Recent observations of galaxy clusters and groups with misalignments between their central AGN jets
and X-ray cavities, or with multiple misaligned cavities, have raised concerns about the jet – bubble
connection in cooling cores, and the processes responsible for jet realignment. To investigate the
frequency and causes of such misalignments, we construct a sample of 16 cool core galaxy clusters and
groups. Using VLBA radio data we measure the parsec-scale position angle of the jets, and compare
it with the position angle of the X-ray cavities detected in Chandra data. Using the overall sample
and selected subsets, we consistently find that there is a 30% – 38% chance to find a misalignment
larger than ∆Ψ = 45◦ when observing a cluster/group with a detected jet and at least one cavity. We
determine that projection may account for an apparently large ∆Ψ only in a fraction of objects (∼35%),
and given that gas dynamical disturbances (as sloshing) are found in both aligned and misaligned
systems, we exclude environmental perturbation as the main driver of cavity – jet misalignment.
Moreover, we find that large misalignments (up to ∼ 90◦
) are favored over smaller ones (45◦ ≤ ∆Ψ ≤
70◦
), and that the change in jet direction can occur on timescales between one and a few tens of Myr.
We conclude that misalignments are more likely related to actual reorientation of the jet axis, and we
discuss several engine-based mechanisms that may cause these dramatic changes.
The document analyzes the merger fractions of radio-loud and radio-quiet active galactic nuclei (AGN) at z > 1 using new Hubble Space Telescope (HST) samples. It finds that 92% (+8%/-14%) of radio-loud galaxies at z > 1 show evidence of recent or ongoing mergers, while only 38% (+16%/-15%) of matched radio-quiet samples exhibit mergers. This provides strong evidence that mergers are the triggering mechanism for radio-loud AGN phenomena like relativistic jet launching, and that major black hole mergers may spin up central supermassive black holes in these objects.
Detection of anisotropic satellite quenching in galaxy clusters up to z ∼ 1Sérgio Sacani
Satellite galaxies in the cluster environment are more likely to be quenched than galaxies in the general field. Recently, it has
been reported that satellite galaxy quenching depends on the orientation relative to their central galaxies: satellites along the
major axis of centrals are more likely to be quenched than those along the minor axis. In this paper, we report a detection
of such anisotropic quenching up to z ∼ 1 based on a large optically selected cluster catalogue constructed from the Hyper
Suprime-Cam Subaru Strategic Program. We calculate the quiescent satellite galaxy fraction as a function of orientation angle
measured from the major axis of central galaxies and find that the quiescent fractions at 0.25 < z < 1 are reasonably fitted
by sinusoidal functions with amplitudes of a few per cent. Anisotropy is clearer in inner regions (<r200m) of clusters and not
significant in cluster outskirts (>r200m). We also confirm that the observed anisotropy cannot be explained by differences in
local galaxy density or stellar mass distribution along the two axes. Quiescent fraction excesses between the two axes suggest
that the quenching efficiency contributing to the anisotropy is almost independent of stellar mass, at least down to our stellar
mass limit of M∗ = 1 × 1010 M. Finally, we argue that the physical origins of the observed anisotropy should have shorter
quenching time-scales than ∼ 1 Gyr, like ram-pressure stripping, because, for anisotropic quenching to be observed, satellites
must be quenched before their initial orientation angles are significantly changed.
HST imaging of star-forming clumps in 6 GASP ram-pressure stripped galaxiesSérgio Sacani
Exploiting broad- and narrow-band images of the Hubble Space Telescope from near-UV to I-band
restframe, we study the star-forming clumps of six galaxies of the GASP sample undergoing strong
ram-pressure stripping (RPS). Clumps are detected in Hα and near-UV, tracing star formation on
different timescales. We consider clumps located in galaxy disks, in the stripped tails and those
formed in stripped gas but still close to the disk, called extraplanar. We detect 2406 Hα-selected
clumps (1708 in disks, 375 in extraplanar regions, and 323 in tails) and 3750 UV-selected clumps (2026
disk clumps, 825 extraplanar clumps and 899 tail clumps). Only ∼ 15% of star-forming clumps are
spatially resolved, meaning that most are smaller than ∼ 140 pc. We study the luminosity and size
distribution functions (LDFs and SDFs, respectively) and the luminosity-size relation. The average
LDF slope is 1.79 ± 0.09, while the average SDF slope is 3.1 ± 0.5. Results suggest the star formation
to be turbulence driven and scale-free, as in main-sequence galaxies. All the clumps, whether they are
in the disks or in the tails, have an enhanced Hα luminosity at a given size, compared to the clumps in
main-sequence galaxies. Indeed, their Hα luminosity is closer to that of clumps in starburst galaxies,
indicating that ram pressure is able to enhance the luminosity. No striking differences are found among
disk and tail clumps, suggesting that the different environments in which they are embedded play a
minor role in influencing the star formation.
HST imaging of star-forming clumps in 6 GASP ram-pressure stripped galaxiesSérgio Sacani
Exploiting broad- and narrow-band images of the Hubble Space Telescope from near-UV to I-band
restframe, we study the star-forming clumps of six galaxies of the GASP sample undergoing strong
ram-pressure stripping (RPS). Clumps are detected in Hα and near-UV, tracing star formation on
different timescales. We consider clumps located in galaxy disks, in the stripped tails and those
formed in stripped gas but still close to the disk, called extraplanar. We detect 2406 Hα-selected
clumps (1708 in disks, 375 in extraplanar regions, and 323 in tails) and 3750 UV-selected clumps (2026
disk clumps, 825 extraplanar clumps and 899 tail clumps). Only ∼ 15% of star-forming clumps are
spatially resolved, meaning that most are smaller than ∼ 140 pc. We study the luminosity and size
distribution functions (LDFs and SDFs, respectively) and the luminosity-size relation. The average
LDF slope is 1.79 ± 0.09, while the average SDF slope is 3.1 ± 0.5. Results suggest the star formation
to be turbulence driven and scale-free, as in main-sequence galaxies. All the clumps, whether they are
in the disks or in the tails, have an enhanced Hα luminosity at a given size, compared to the clumps in
main-sequence galaxies. Indeed, their Hα luminosity is closer to that of clumps in starburst galaxies,
indicating that ram pressure is able to enhance the luminosity. No striking differences are found among
disk and tail clumps, suggesting that the different environments in which they are embedded play a
minor role in influencing the star formation.
HST imaging of star-forming clumps in 6 GASP ram-pressure stripped galaxiesSérgio Sacani
Exploiting broad- and narrow-band images of the Hubble Space Telescope from near-UV to I-band
restframe, we study the star-forming clumps of six galaxies of the GASP sample undergoing strong
ram-pressure stripping (RPS). Clumps are detected in Hα and near-UV, tracing star formation on
different timescales. We consider clumps located in galaxy disks, in the stripped tails and those
formed in stripped gas but still close to the disk, called extraplanar. We detect 2406 Hα-selected
clumps (1708 in disks, 375 in extraplanar regions, and 323 in tails) and 3750 UV-selected clumps (2026
disk clumps, 825 extraplanar clumps and 899 tail clumps). Only ∼ 15% of star-forming clumps are
spatially resolved, meaning that most are smaller than ∼ 140 pc. We study the luminosity and size
distribution functions (LDFs and SDFs, respectively) and the luminosity-size relation. The average
LDF slope is 1.79 ± 0.09, while the average SDF slope is 3.1 ± 0.5. Results suggest the star formation
to be turbulence driven and scale-free, as in main-sequence galaxies. All the clumps, whether they are
in the disks or in the tails, have an enhanced Hα luminosity at a given size, compared to the clumps in
main-sequence galaxies. Indeed, their Hα luminosity is closer to that of clumps in starburst galaxies,
indicating that ram pressure is able to enhance the luminosity. No striking differences are found among
disk and tail clumps, suggesting that the different environments in which they are embedded play a
minor role in influencing the star formation.
Search for an Isotropic Gravitational-wave Background with the Parkes Pulsar ...Sérgio Sacani
Pulsar timing arrays aim to detect nanohertz-frequency gravitational waves (GWs). A background of GWs
modulates pulsar arrival times and manifests as a stochastic process, common to all pulsars, with a signature spatial
correlation. Here we describe a search for an isotropic stochastic gravitational-wave background (GWB) using
observations of 30 millisecond pulsars from the third data release of the Parkes Pulsar Timing Array (PPTA), which
spans 18 yr. Using current Bayesian inference techniques we recover and characterize a common-spectrum noise
process. Represented as a strain spectrum h Af c 1yr = -1 a ( ) , we measure A 3.1 10 0.9 = ´ 1.3 15 -
+ - and
α = −0.45 ± 0.20, respectively (median and 68% credible interval). For a spectral index of α = −2/3,
corresponding to an isotropic background of GWs radiated by inspiraling supermassive black hole binaries, we
recover an amplitude of A 2.04 10 0.22 = ´ 0.25 15 -
+ - . However, we demonstrate that the apparent signal strength is timedependent, as the first half of our data set can be used to place an upper limit on A that is in tension with the inferred
common-spectrum amplitude using the complete data set. We search for spatial correlations in the observations by
hierarchically analyzing individual pulsar pairs, which also allows for significance validation through randomizing
pulsar positions on the sky. For a process with α = −2/3, we measure spatial correlations consistent with a GWB,
with an estimated false-alarm probability of p 0.02 (approx. 2σ). The long timing baselines of the PPTA and the
access to southern pulsars will continue to play an important role in the International Pulsar Timing Array.
AT2023fhn (the Finch): a Luminous Fast Blue Optical Transient at a large offs...Sérgio Sacani
Luminous Fast Blue Optical Transients (LFBOTs) - the prototypical example being AT 2018cow - are a rare class of events
whose origins are poorly understood. They are characterised by rapid evolution, featureless blue spectra at early times, and
luminous X-ray and radio emission. LFBOTs thus far have been found exclusively at small projected offsets from star-forming
host galaxies. We present Hubble Space Telescope, Gemini, Chandra and Very Large Array observations of a new LFBOT,
AT 2023fhn. The Hubble Space Telescope data reveal a large offset (> 3.5 half-light radii) from the two closest galaxies, both
at redshift 𝑧 ∼ 0.24. The location of AT 2023fhn is in stark contrast with previous events, and demonstrates that LFBOTs can
occur in a range of galactic environments.
Hydrogen Column Density Variability in a Sample of Local Compton-Thin AGNSérgio Sacani
We present the analysis of multiepoch observations of a set of 12 variable, Compton-thin, local (z<0.1) active galactic nuclei (AGN) selected from the 100-month BAT catalog. We analyze all available X-ray data from Chandra, XMMNewton, and NuSTAR, adding up to a total of 53 individual observations. This corresponds to between 3 and 7 observations per source, probing variability timescales between a few days and ∼ 20 yr. All sources have at least one NuSTAR observation, ensuring high-energy coverage, which allows us to disentangle the line-of-sight and reflection components in the X-ray spectra. For each source, we model all available spectra simultaneously, using the physical torus models MYTorus, borus02, and UXCLUMPY. The simultaneous fitting, along with the high-energy coverage, allows us to place tight constraints on torus parameters such as the torus covering factor, inclination angle, and torus average column density. We also estimate the line-of-sight column density (NH) for each individual observation. Within the 12 sources, we detect clear line-of-sight NH variability in 5, non-variability in 5, and for 2 of them it is not possible to fully disentangle intrinsic-luminosity and NH variability. We observe large differences between the average values of line-ofsight NH (or NH of the obscurer) and the average NH of the torus (or NH of the reflector), for each source, by a factor between ∼ 2 to > 100. This behavior, which suggests a physical disconnect between the absorber and the reflector, is more extreme in sources that present NH variability. NH-variable AGN also tend to present larger obscuration and broader cloud distributions than their non-variable counterparts. We observe that large changes in obscuration only occur at long timescales, and use this to place tentative lower limits on torus cloud sizes.
The document analyzes the merger fractions of radio-loud and radio-quiet active galactic nuclei (AGN) at z > 1 using new Hubble Space Telescope (HST) samples. It finds that 92% (+8%/-14%) of radio-loud galaxies at z > 1 show evidence of recent or ongoing mergers, while only 38% (+16%/-15%) of matched radio-quiet samples exhibit mergers. This provides strong evidence that mergers are the triggering mechanism for radio-loud AGN phenomena like relativistic jet launching, and that major black hole mergers may spin up central supermassive black holes in these objects.
Detection of anisotropic satellite quenching in galaxy clusters up to z ∼ 1Sérgio Sacani
Satellite galaxies in the cluster environment are more likely to be quenched than galaxies in the general field. Recently, it has
been reported that satellite galaxy quenching depends on the orientation relative to their central galaxies: satellites along the
major axis of centrals are more likely to be quenched than those along the minor axis. In this paper, we report a detection
of such anisotropic quenching up to z ∼ 1 based on a large optically selected cluster catalogue constructed from the Hyper
Suprime-Cam Subaru Strategic Program. We calculate the quiescent satellite galaxy fraction as a function of orientation angle
measured from the major axis of central galaxies and find that the quiescent fractions at 0.25 < z < 1 are reasonably fitted
by sinusoidal functions with amplitudes of a few per cent. Anisotropy is clearer in inner regions (<r200m) of clusters and not
significant in cluster outskirts (>r200m). We also confirm that the observed anisotropy cannot be explained by differences in
local galaxy density or stellar mass distribution along the two axes. Quiescent fraction excesses between the two axes suggest
that the quenching efficiency contributing to the anisotropy is almost independent of stellar mass, at least down to our stellar
mass limit of M∗ = 1 × 1010 M. Finally, we argue that the physical origins of the observed anisotropy should have shorter
quenching time-scales than ∼ 1 Gyr, like ram-pressure stripping, because, for anisotropic quenching to be observed, satellites
must be quenched before their initial orientation angles are significantly changed.
HST imaging of star-forming clumps in 6 GASP ram-pressure stripped galaxiesSérgio Sacani
Exploiting broad- and narrow-band images of the Hubble Space Telescope from near-UV to I-band
restframe, we study the star-forming clumps of six galaxies of the GASP sample undergoing strong
ram-pressure stripping (RPS). Clumps are detected in Hα and near-UV, tracing star formation on
different timescales. We consider clumps located in galaxy disks, in the stripped tails and those
formed in stripped gas but still close to the disk, called extraplanar. We detect 2406 Hα-selected
clumps (1708 in disks, 375 in extraplanar regions, and 323 in tails) and 3750 UV-selected clumps (2026
disk clumps, 825 extraplanar clumps and 899 tail clumps). Only ∼ 15% of star-forming clumps are
spatially resolved, meaning that most are smaller than ∼ 140 pc. We study the luminosity and size
distribution functions (LDFs and SDFs, respectively) and the luminosity-size relation. The average
LDF slope is 1.79 ± 0.09, while the average SDF slope is 3.1 ± 0.5. Results suggest the star formation
to be turbulence driven and scale-free, as in main-sequence galaxies. All the clumps, whether they are
in the disks or in the tails, have an enhanced Hα luminosity at a given size, compared to the clumps in
main-sequence galaxies. Indeed, their Hα luminosity is closer to that of clumps in starburst galaxies,
indicating that ram pressure is able to enhance the luminosity. No striking differences are found among
disk and tail clumps, suggesting that the different environments in which they are embedded play a
minor role in influencing the star formation.
HST imaging of star-forming clumps in 6 GASP ram-pressure stripped galaxiesSérgio Sacani
Exploiting broad- and narrow-band images of the Hubble Space Telescope from near-UV to I-band
restframe, we study the star-forming clumps of six galaxies of the GASP sample undergoing strong
ram-pressure stripping (RPS). Clumps are detected in Hα and near-UV, tracing star formation on
different timescales. We consider clumps located in galaxy disks, in the stripped tails and those
formed in stripped gas but still close to the disk, called extraplanar. We detect 2406 Hα-selected
clumps (1708 in disks, 375 in extraplanar regions, and 323 in tails) and 3750 UV-selected clumps (2026
disk clumps, 825 extraplanar clumps and 899 tail clumps). Only ∼ 15% of star-forming clumps are
spatially resolved, meaning that most are smaller than ∼ 140 pc. We study the luminosity and size
distribution functions (LDFs and SDFs, respectively) and the luminosity-size relation. The average
LDF slope is 1.79 ± 0.09, while the average SDF slope is 3.1 ± 0.5. Results suggest the star formation
to be turbulence driven and scale-free, as in main-sequence galaxies. All the clumps, whether they are
in the disks or in the tails, have an enhanced Hα luminosity at a given size, compared to the clumps in
main-sequence galaxies. Indeed, their Hα luminosity is closer to that of clumps in starburst galaxies,
indicating that ram pressure is able to enhance the luminosity. No striking differences are found among
disk and tail clumps, suggesting that the different environments in which they are embedded play a
minor role in influencing the star formation.
HST imaging of star-forming clumps in 6 GASP ram-pressure stripped galaxiesSérgio Sacani
Exploiting broad- and narrow-band images of the Hubble Space Telescope from near-UV to I-band
restframe, we study the star-forming clumps of six galaxies of the GASP sample undergoing strong
ram-pressure stripping (RPS). Clumps are detected in Hα and near-UV, tracing star formation on
different timescales. We consider clumps located in galaxy disks, in the stripped tails and those
formed in stripped gas but still close to the disk, called extraplanar. We detect 2406 Hα-selected
clumps (1708 in disks, 375 in extraplanar regions, and 323 in tails) and 3750 UV-selected clumps (2026
disk clumps, 825 extraplanar clumps and 899 tail clumps). Only ∼ 15% of star-forming clumps are
spatially resolved, meaning that most are smaller than ∼ 140 pc. We study the luminosity and size
distribution functions (LDFs and SDFs, respectively) and the luminosity-size relation. The average
LDF slope is 1.79 ± 0.09, while the average SDF slope is 3.1 ± 0.5. Results suggest the star formation
to be turbulence driven and scale-free, as in main-sequence galaxies. All the clumps, whether they are
in the disks or in the tails, have an enhanced Hα luminosity at a given size, compared to the clumps in
main-sequence galaxies. Indeed, their Hα luminosity is closer to that of clumps in starburst galaxies,
indicating that ram pressure is able to enhance the luminosity. No striking differences are found among
disk and tail clumps, suggesting that the different environments in which they are embedded play a
minor role in influencing the star formation.
Search for an Isotropic Gravitational-wave Background with the Parkes Pulsar ...Sérgio Sacani
Pulsar timing arrays aim to detect nanohertz-frequency gravitational waves (GWs). A background of GWs
modulates pulsar arrival times and manifests as a stochastic process, common to all pulsars, with a signature spatial
correlation. Here we describe a search for an isotropic stochastic gravitational-wave background (GWB) using
observations of 30 millisecond pulsars from the third data release of the Parkes Pulsar Timing Array (PPTA), which
spans 18 yr. Using current Bayesian inference techniques we recover and characterize a common-spectrum noise
process. Represented as a strain spectrum h Af c 1yr = -1 a ( ) , we measure A 3.1 10 0.9 = ´ 1.3 15 -
+ - and
α = −0.45 ± 0.20, respectively (median and 68% credible interval). For a spectral index of α = −2/3,
corresponding to an isotropic background of GWs radiated by inspiraling supermassive black hole binaries, we
recover an amplitude of A 2.04 10 0.22 = ´ 0.25 15 -
+ - . However, we demonstrate that the apparent signal strength is timedependent, as the first half of our data set can be used to place an upper limit on A that is in tension with the inferred
common-spectrum amplitude using the complete data set. We search for spatial correlations in the observations by
hierarchically analyzing individual pulsar pairs, which also allows for significance validation through randomizing
pulsar positions on the sky. For a process with α = −2/3, we measure spatial correlations consistent with a GWB,
with an estimated false-alarm probability of p 0.02 (approx. 2σ). The long timing baselines of the PPTA and the
access to southern pulsars will continue to play an important role in the International Pulsar Timing Array.
AT2023fhn (the Finch): a Luminous Fast Blue Optical Transient at a large offs...Sérgio Sacani
Luminous Fast Blue Optical Transients (LFBOTs) - the prototypical example being AT 2018cow - are a rare class of events
whose origins are poorly understood. They are characterised by rapid evolution, featureless blue spectra at early times, and
luminous X-ray and radio emission. LFBOTs thus far have been found exclusively at small projected offsets from star-forming
host galaxies. We present Hubble Space Telescope, Gemini, Chandra and Very Large Array observations of a new LFBOT,
AT 2023fhn. The Hubble Space Telescope data reveal a large offset (> 3.5 half-light radii) from the two closest galaxies, both
at redshift 𝑧 ∼ 0.24. The location of AT 2023fhn is in stark contrast with previous events, and demonstrates that LFBOTs can
occur in a range of galactic environments.
Hydrogen Column Density Variability in a Sample of Local Compton-Thin AGNSérgio Sacani
We present the analysis of multiepoch observations of a set of 12 variable, Compton-thin, local (z<0.1) active galactic nuclei (AGN) selected from the 100-month BAT catalog. We analyze all available X-ray data from Chandra, XMMNewton, and NuSTAR, adding up to a total of 53 individual observations. This corresponds to between 3 and 7 observations per source, probing variability timescales between a few days and ∼ 20 yr. All sources have at least one NuSTAR observation, ensuring high-energy coverage, which allows us to disentangle the line-of-sight and reflection components in the X-ray spectra. For each source, we model all available spectra simultaneously, using the physical torus models MYTorus, borus02, and UXCLUMPY. The simultaneous fitting, along with the high-energy coverage, allows us to place tight constraints on torus parameters such as the torus covering factor, inclination angle, and torus average column density. We also estimate the line-of-sight column density (NH) for each individual observation. Within the 12 sources, we detect clear line-of-sight NH variability in 5, non-variability in 5, and for 2 of them it is not possible to fully disentangle intrinsic-luminosity and NH variability. We observe large differences between the average values of line-ofsight NH (or NH of the obscurer) and the average NH of the torus (or NH of the reflector), for each source, by a factor between ∼ 2 to > 100. This behavior, which suggests a physical disconnect between the absorber and the reflector, is more extreme in sources that present NH variability. NH-variable AGN also tend to present larger obscuration and broader cloud distributions than their non-variable counterparts. We observe that large changes in obscuration only occur at long timescales, and use this to place tentative lower limits on torus cloud sizes.
The SPHERE view of three interacting twin disc systems in polarised lightSérgio Sacani
Dense stellar environments as hosts of ongoing star formation increase the probability of gravitational encounters among stellar
systems during the early stages of evolution. Stellar interaction may occur through non-recurring, hyperbolic or parabolic passages
(a so-called ‘fly-by’), through secular binary evolution, or through binary capture. In all three scenarios, the strong gravitational
perturbation is expected to manifest itself in the disc structures around the individual stars. Here, we present near-infrared
polarised light observations that were taken with the SPHERE/IRDIS instrument of three known interacting twin-disc systems:
AS 205, EM* SR 24, and FU Orionis. The scattered light exposes spirals likely caused by the gravitational interaction. On
a larger scale, we observe connecting filaments between the stars. We analyse their very complex polarised intensity and put
particular attention to the presence of multiple light sources in these systems. The local angle of linear polarisation indicates
the source whose light dominates the scattering process from the bridging region between the two stars. Further, we show
that the polarised intensity from scattering with multiple relevant light sources results from an incoherent summation of the
individuals’ contribution. This can produce nulls of polarised intensity in an image, as potentially observed in AS 205.We discuss
the geometry and content of the systems by comparing the polarised light observations with other data at similar resolution,
namely with ALMA continuum and gas emission. Collective observational data can constrain the systems’ geometry and stellar
trajectories, with the important potential to differentiate between dynamical scenarios of stellar interaction.
Galaxy interactions are the dominant trigger for local type 2 quasarsSérgio Sacani
The triggering mechanism for the most luminous, quasar-like active galactic nuclei (AGN) remains a source of debate, with
some studies favouring triggering via galaxy mergers, but others finding little evidence to support this mechanism. Here, we
present deep Isaac Newton Telescope/Wide Field Camera imaging observations of a complete sample of 48 optically selected
type 2 quasars – the QSOFEED sample (L[O III] > 108.5 L; z < 0.14). Based on visual inspection by eight classifiers, we find
clear evidence that galaxy interactions are the dominant triggering mechanism for quasar activity in the local universe, with
65+6
−7 per cent of the type 2 quasar hosts showing morphological features consistent with galaxy mergers or encounters, compared
with only 22+5
−4 per cent of a stellar-mass- and redshift-matched comparison sample of non-AGN galaxies – a 5σ difference. The
type 2 quasar hosts are a factor of 3.0+0.5 −0.8 more likely to be morphologically disturbed than their matched non-AGN counterparts,
similar to our previous results for powerful 3CR radio AGN of comparable [O III] emission-line luminosity and redshift. In
contrast to the idea that quasars are triggered at the peaks of galaxy mergers as the two nuclei coalesce, and only become
visible post-coalescence, the majority of morphologically disturbed type 2 quasar sources in our sample are observed in the
pre-coalescence phase (61+8
−9 per cent). We argue that much of the apparent ambiguity that surrounds observational results in this
field is a result of differences in the surface brightness depths of the observations, combined with the effects of cosmological
surface brightness dimming.
The network of filaments with embedded clusters surrounding voids, which has been seen in maps derived from
redshift surveys and reproduced in simulations, has been referred to as the cosmic web. A complementary
description is provided by considering the shear in the velocity field of galaxies. The eigenvalues of the shear
provide information regarding whether or not a region is collapsing in three dimensions, which is the condition for
a knot, expanding in three dimensions, which is the condition for a void, or in the intermediate condition of a
filament or sheet. The structures that are quantitatively defined by the eigenvalues can be approximated by isocontours
that provide a visual representation of the cosmic velocity (V) web. The current application is based on
radial peculiar velocities from the Cosmicflows-2 collection of distances. The three-dimensional velocity field is
constructed using the Wiener filter methodology in the linear approximation. Eigenvalues of the velocity shear are
calculated at each point on a grid. Here, knots and filaments are visualized across a local domain of
diameter ~0.1c
Os astrônomos descobriram um processo único sobre como as maiores galáxias elípticas do universo continuam gerando estrelas muito tempo depois do anos de pico de nascimentos estelares. A alta resolução e a sensibilidade à radiação ultravioleta do Hubble, permitiu aos astrônomos observarem nós brilhantes de estrelas azuis, quentes, se formando juntamente com jatos de buracos negros ativos encontrados nos centros das gigantescas galáxias elípticas.
Combinando dados do Huubble com observações feitas por um conjunto de telescópios baseados tanto em Terra como no espaço, duas equipes independentes descobriram que os jatos dos buracos negros, e as estrelas recém-nascidas são todos partes de um ciclo auto-regulado. Jatos de alta energia atirados do buraco negro aquecem um halo de gás circulante, controlando a taxa com a qual o gás esfria e cai na galáxia.
“Pense no gás ao redor da galáxia como uma atmosfera”, explicou o líder do primeiro estudo, Megan Donahue, da Universidade Estadual do Michigan. “Essa atmosfera pode conter material em diferentes estados, do mesmo modo que a nossa atmosfera tem gás, nuvens e chuva. O que nós estamos vendo é um processo parecido com uma tempestade. À medida que os jatos impulsionam o gás para fora do centro da galáxia, parte do gás esfria e precipita em aglomerados frios que caem de volta para o centro da galáxia como gotas de chuvas”.
“As gotas de chuva eventualmente esfriam o suficiente para tornar-se nuvens de formação de estrelas de gás frio molecular, e a capacidade de observar no ultravioleta distante do Hubble, nos permitiu observar diretamente esses chuviscos de formação de estrelas”, explicou o líder do segundo estudo, Grant Tremblay, da Universidade de Yale. “Nós sabemos que esses chuviscos estão linkados com os jatos, pois eles foram encontrados em filamentos que se dobram ao redor dos jatos, ou abraçam as bordas de bolhas gigantes que os jatos inflaram”, disse Tremblay. “E eles terminam fazendo um redemoinho de gás de formação de estrelas ao redor do buraco negro central”.
Evidence for the_thermal_sunyaev-zeldovich_effect_associated_with_quasar_feed...Sérgio Sacani
Using a radio-quiet subsample of the Sloan Digital Sky Survey spectroscopic quasar
catalogue, spanning redshifts 0.5–3.5, we derive the mean millimetre and far-infrared
quasar spectral energy distributions (SEDs) via a stacking analysis of Atacama Cosmology
Telescope and Herschel-Spectral and Photometric Imaging REceiver data. We
constrain the form of the far-infrared emission and find 3σ–4σ evidence for the thermal
Sunyaev-Zel’dovich (SZ) effect, characteristic of a hot ionized gas component with
thermal energy (6.2 ± 1.7) × 1060 erg. This amount of thermal energy is greater than
expected assuming only hot gas in virial equilibrium with the dark matter haloes of
(1 − 5) × 1012h
−1M that these systems are expected to occupy, though the highest
quasar mass estimates found in the literature could explain a large fraction of this
energy. Our measurements are consistent with quasars depositing up to (14.5±3.3) τ
−1
8
per cent of their radiative energy into their circumgalactic environment if their typical
period of quasar activity is τ8 × 108 yr. For high quasar host masses, ∼ 1013h
−1M,
this percentage will be reduced. Furthermore, the uncertainty on this percentage is
only statistical and additional systematic uncertainties enter at the 40 per cent level.
The SEDs are dust dominated in all bands and we consider various models for dust
emission. While sufficiently complex dust models can obviate the SZ effect, the SZ
interpretation remains favoured at the 3σ–4σ level for most models.
This document summarizes evidence that submillimeter galaxies (SMGs) at redshift 3-6 may be progenitors of compact quiescent galaxies observed at redshift 2. It compares properties of a sample of z~2 quiescent galaxies with a statistical sample of z>3 SMGs in the COSMOS field. It finds that the formation redshifts of the z~2 galaxies match the observed redshift distribution of z>3 SMGs. It also finds that the space densities and properties such as sizes, stellar masses, and internal velocities of the two populations are consistent with an evolutionary connection, assuming SMG starbursts have a duty cycle of 42+40 Myr. This suggests SMGs may represent an early burst
Identification of Superclusters and Their Properties in the Sloan Digital Sky...Sérgio Sacani
Superclusters are the largest massive structures in the cosmic web, on tens to hundreds of megaparsec scales. They
are the largest assembly of galaxy clusters in the Universe. Apart from a few detailed studies of such structures,
their evolutionary mechanism is still an open question. In order to address and answer the relevant questions, a
statistically significant, large catalog of superclusters covering a wide range of redshifts and sky areas is essential.
Here, we present a large catalog of 662 superclusters identified using a modified friends-of-friends algorithm
applied on the WHL (Wen–Han–Liu) cluster catalog within a redshift range of 0.05 z 0.42. We name the most
massive supercluster at z ∼ 0.25 as the Einasto Supercluster. We find that the median mass of superclusters is
∼5.8 × 10 15 Me and the median size ∼65 Mpc. We find that the supercluster environment slightly affects the
growth of clusters. We compare the properties of the observed superclusters with the mock superclusters extracted
from the Horizon Run 4 cosmological simulation. The properties of the superclusters in the mocks and
observations are in broad agreement. We find that the density contrast of a supercluster is correlated with its
maximum extent with a power-law index, α ∼ −2. The phase-space distribution of mock superclusters shows that,
on average, ∼90% of part of a supercluster has a gravitational influence on its constituents. We also show the mock
halos’ average number density and peculiar velocity profiles in and around the superclusters.
Imaging the Milky Way with Millihertz Gravitational WavesSérgio Sacani
Modern astronomers enjoy access to all-sky images across a wide range of the electromagnetic spectrum from
long-wavelength radio to high-energy gamma rays. The most prominent feature in many of these images is our
own Galaxy, with different features revealed in each wave band. Gravitational waves (GWs) have recently been
added to the astronomers’ toolkit as a nonelectromagnetic messenger. To date, all identified GW sources have been
extra-Galactic and transient. However, the Milky Way hosts a population of ultracompact binaries (UCBs), which
radiate persistent GWs in the milliHertz band that is not observable with today’s terrestrial gravitational-wave
detectors. Space-based detectors such as the Laser Interferometer Space Antenna will measure this population and
provide a census of their location, masses, and orbital properties. In this work, we will show how this data can be
used to form a false-color image of the Galaxy that represents the intensity and frequency of the gravitational
waves produced by the UCB population. Such images can be used to study the morphology of the Galaxy, identify
interesting multimessenger sources through cross-matching, and for educational and outreach purposes.
The most luminous_galaxies_discovered_by_wiseSérgio Sacani
This document presents a sample of 20 extremely luminous galaxies discovered by the Wide-field Infrared Survey Explorer (WISE). Five of these galaxies have infrared luminosities exceeding 1014 solar luminosities, the highest infrared luminosity threshold yet observed. They were selected using criteria requiring weak or no detection in the first two WISE bands but strong detections in the third and fourth bands. Spectral energy distribution modeling suggests their high luminosities are powered by obscured active galactic nuclei with hot dust temperatures around 450 Kelvin. The existence of such luminous galaxies at redshifts above 3 provides constraints on the early growth of supermassive black holes through rapid accretion.
This document summarizes observations of the lensed galaxy HATLAS J142935.3-002836 (H1429-0028) from the Herschel-ATLAS survey. Optical spectroscopy revealed the foreground lens is at redshift 0.218, while the background galaxy is at redshift 1.027. High-resolution imaging from Hubble Space Telescope and Keck adaptive optics show the background galaxy is comprised of two components and a tidal tail, resembling a major merger. Analysis of ALMA observations of CO emission provides a dynamical mass estimate of one component as 5.8 ± 1.7 × 1010 M☉. Modeling of the spectral energy distribution indicates the total stellar mass is 1.32
The abundance of_x_shpoaed_radio_sources_implications_for_the_gravitational_w...Sérgio Sacani
Devem existir menos buracos negros supermassivos binários nos núcleos das galáxias do que se pensava anteriormente, disse uma equipe de cientistas da Universidade de Brandeis em Waltaham, Massachussets, e do Instituto de Pesquisa Raman em Bangalore, na Índia.
A maior parte das galáxias massivas no universo devem abrigar no mínimo um buraco negro supermassivo em seus núcleos.
Quando duas galáxias colidem, seus buracos negros se juntam, formando uma dança colossal que resulta numa combinação de par. Esse processo é a mais intensa fonte de ondas gravitacionais no universo, que ainda precisam ser diretamente detectadas.
“As ondas gravitacionais representam a próxima fronteira da astrofísica, e sua detecção levará a novas ideias sobre o universo. É importante se ter a maior quantidade de informação possível sobre as fontes dessas ondas”, disse o Dr. David Roberts, um membro da equipe da Universidade de Brandeis.
Dust in the_polar_region_as_a_major_contributor_to_the_infrared_emission_of_a...Sérgio Sacani
The mid-infrared emission of the active galactic nucleus NGC 3783 was observed using interferometry over multiple epochs, providing dense coverage of position angles and baselines. The emission was found to be strongly elongated along a position angle of -52 degrees, closely aligned with the polar axis orientation of -45 degrees. The half-light radii were measured to be 20.0 mas by 6.7 mas, corresponding to an axis ratio of 3:1. This implies that 60-90% of the 8-13 micron emission is from the polar-elongated component. The observations support a scenario where the majority of mid-infrared emission in Seyfert galaxies originates from a dusty wind in the polar region,
Is the atmosphere of the ultra-hot Jupiter WASP-121 b variable?Sérgio Sacani
We present a comprehensive analysis of the Hubble Space Telescope observations of the atmosphere
of WASP-121 b, a ultra-hot Jupiter. After reducing the transit, eclipse, and phase-curve observations
with a uniform methodology and addressing the biases from instrument systematics, sophisticated
atmospheric retrievals are used to extract robust constraints on the thermal structure, chemistry, and
cloud properties of the atmosphere. Our analysis shows that the observations are consistent with a
strong thermal inversion beginning at ∼104 Pa on the dayside, solar to subsolar metallicity Z (i.e.,
−0.77 < log(Z) < 0.05), and super-solar C/O ratio (i.e., 0.59 < C/O < 0.87). More importantly,
utilizing the high signal-to-noise ratio and repeated observations of the planet, we identify the following
unambiguous time-varying signals in the data: i) a shift of the putative hotspot offset between the
two phase-curves and ii) varying spectral signatures in the transits and eclipses. By simulating the
global dynamics of WASP-121 b atmosphere at high-resolution, we show that the identified signals are
consistent with quasi-periodic weather patterns, hence atmospheric variability, with signatures at the
level probed by the observations (∼5% to ∼10%) that change on a timescale of ∼5 planet days; in
the simulations, the weather patterns arise from the formation and movement of storms and fronts,
causing hot (as well as cold) patches of atmosphere to deform, separate, and mix in time.
A spectroscopic sample_of_massive_galaxiesSérgio Sacani
This document describes a study of 16 massive galaxies at z ~ 2 selected from the 3D-HST spectroscopic survey based on the detection of a strong 4000 Angstrom break in their spectra. Spectroscopy and imaging from HST/WFC3 are used to determine accurate redshifts, stellar population properties, and structural parameters. The sample significantly increases the number of spectroscopically confirmed evolved galaxies at z ~ 2 with robust size measurements. The analysis populates the mass-size relation and finds it is consistent with local relations but with smaller sizes by a factor of 2-3. A model is presented where the observed size evolution is explained by quenching of increasingly larger star-forming galaxies at a rate set by
DISCOVERY OF A GALAXY CLUSTER WITH A VIOLENTLY STARBURSTING CORE AT z = 2:506Sérgio Sacani
We report the discovery of a remarkable concentration of massive galaxies with extended X-ray
emission at zspec = 2:506, which contains 11 massive (M & 1011M) galaxies in the central 80kpc
region (11.6 overdensity). We have spectroscopically conrmed 17 member galaxies with 11 from CO
and the remaining ones from H. The X-ray luminosity, stellar mass content and velocity dispersion
all point to a collapsed, cluster-sized dark matter halo with mass M200c = 1013:90:2M, making it
the most distant X-ray-detected cluster known to date. Unlike other clusters discovered so far, this
structure is dominated by star-forming galaxies (SFGs) in the core with only 2 out of the 11 massive
galaxies classied as quiescent. The star formation rate (SFR) in the 80kpc core reaches 3400 M
yr 1 with a gas depletion time of 200 Myr, suggesting that we caught this cluster in rapid build-up
of a dense core. The high SFR is driven by both a high abundance of SFGs and a higher starburst
fraction ( 25%, compared to 3%-5% in the eld). The presence of both a collapsed, cluster-sized
halo and a predominant population of massive SFGs suggests that this structure could represent an
important transition phase between protoclusters and mature clusters. It provides evidence that the
main phase of massive galaxy passivization will take place after galaxies accrete onto the cluster,
providing new insights into massive cluster formation at early epochs. The large integrated stellar
mass at such high redshift challenges our understanding of massive cluster formation.
A giant ring_like_structure_at_078_z_086_displayed_by_gr_bsSérgio Sacani
This document describes the discovery of a giant ring-like structure in the observable universe displayed by 9 gamma ray bursts (GRBs) between redshifts of 0.78 and 0.86. The ring has a diameter of 1720 Mpc, over five times larger than the expected transition scale to homogeneity. The ring lies at a distance of 2770 Mpc with major and minor diameters of 43° and 30°, respectively. The probability of this structure occurring by random chance is calculated to be 2 × 10-6. This ring-shaped feature contradicts the cosmological principle of large-scale homogeneity and isotropy, and the physical mechanism responsible is unknown.
The galaxy morphology–density relation in the EAGLE simulationSérgio Sacani
This study uses a convolutional neural network trained on observed galaxy images to classify galaxies in the EAGLE cosmological hydrodynamical simulation by visual morphology. It finds that EAGLE reproduces both the observed relationships between galaxy morphology and local density (the morphology-density relation), and between morphology and galaxy mass. Through analysis of the simulations, the key processes identified as driving the morphology-density relation are: (1) the transformation of disc galaxies into lenticular galaxies via gas stripping in dense environments, (2) the formation of lenticular galaxies through merger-induced black hole feedback in less dense environments, and (3) the increasing fraction of more elliptical, high-mass galaxies at higher densities.
Storm in teacup_a_radio_quiet_quasar_with_radio_emitting_bubblesSérgio Sacani
Artigo descreve descoberta feita com o VLA de uma tempestade nas ondas de rádio em uma galáxia até então calma, o que traz conclusões sobre a evolução das galáxias.
A High-mass, Young Star-forming Core Escaping from Its Parental FilamentSérgio Sacani
We studied the unique kinematic properties in massive filament G352.63-1.07 at 103 au spatial scale with the dense
molecular tracers observed with the Atacama Large Millimeter/submillimeter Array. We find the central massive
core M1 (12 Me) being separated from the surrounding filament with a velocity difference of
- =- - v vsys 2 km s 1 and a transverse separation within 3″. Meanwhile, as shown in multiple dense-gas
tracers, M1 has a spatial extension closely aligned with the main filament and is connected to the filament toward
both its ends. M1 thus represents a very beginning state for a massive, young star-forming core escaping from the
parental filament, within a timescale of ∼4000 yr. Based on its kinetic energy (3.5 × 1044 erg), the core escape is
unlikely solely due to the original filament motion or magnetic field but requires more energetic events such as a
rapid intense anisotropic collapse. The released energy also seems to noticeably increase the environmental
turbulence. This may help the filament to become stabilized again.
The binding of cosmological structures by massless topological defectsSérgio Sacani
Assuming spherical symmetry and weak field, it is shown that if one solves the Poisson equation or the Einstein field
equations sourced by a topological defect, i.e. a singularity of a very specific form, the result is a localized gravitational
field capable of driving flat rotation (i.e. Keplerian circular orbits at a constant speed for all radii) of test masses on a thin
spherical shell without any underlying mass. Moreover, a large-scale structure which exploits this solution by assembling
concentrically a number of such topological defects can establish a flat stellar or galactic rotation curve, and can also deflect
light in the same manner as an equipotential (isothermal) sphere. Thus, the need for dark matter or modified gravity theory is
mitigated, at least in part.
EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Weste...Sérgio Sacani
Context. With a mass exceeding several 104 M⊙ and a rich and dense population of massive stars, supermassive young star clusters
represent the most massive star-forming environment that is dominated by the feedback from massive stars and gravitational interactions
among stars.
Aims. In this paper we present the Extended Westerlund 1 and 2 Open Clusters Survey (EWOCS) project, which aims to investigate
the influence of the starburst environment on the formation of stars and planets, and on the evolution of both low and high mass stars.
The primary targets of this project are Westerlund 1 and 2, the closest supermassive star clusters to the Sun.
Methods. The project is based primarily on recent observations conducted with the Chandra and JWST observatories. Specifically,
the Chandra survey of Westerlund 1 consists of 36 new ACIS-I observations, nearly co-pointed, for a total exposure time of 1 Msec.
Additionally, we included 8 archival Chandra/ACIS-S observations. This paper presents the resulting catalog of X-ray sources within
and around Westerlund 1. Sources were detected by combining various existing methods, and photon extraction and source validation
were carried out using the ACIS-Extract software.
Results. The EWOCS X-ray catalog comprises 5963 validated sources out of the 9420 initially provided to ACIS-Extract, reaching a
photon flux threshold of approximately 2 × 10−8 photons cm−2
s
−1
. The X-ray sources exhibit a highly concentrated spatial distribution,
with 1075 sources located within the central 1 arcmin. We have successfully detected X-ray emissions from 126 out of the 166 known
massive stars of the cluster, and we have collected over 71 000 photons from the magnetar CXO J164710.20-455217.
More Related Content
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The SPHERE view of three interacting twin disc systems in polarised lightSérgio Sacani
Dense stellar environments as hosts of ongoing star formation increase the probability of gravitational encounters among stellar
systems during the early stages of evolution. Stellar interaction may occur through non-recurring, hyperbolic or parabolic passages
(a so-called ‘fly-by’), through secular binary evolution, or through binary capture. In all three scenarios, the strong gravitational
perturbation is expected to manifest itself in the disc structures around the individual stars. Here, we present near-infrared
polarised light observations that were taken with the SPHERE/IRDIS instrument of three known interacting twin-disc systems:
AS 205, EM* SR 24, and FU Orionis. The scattered light exposes spirals likely caused by the gravitational interaction. On
a larger scale, we observe connecting filaments between the stars. We analyse their very complex polarised intensity and put
particular attention to the presence of multiple light sources in these systems. The local angle of linear polarisation indicates
the source whose light dominates the scattering process from the bridging region between the two stars. Further, we show
that the polarised intensity from scattering with multiple relevant light sources results from an incoherent summation of the
individuals’ contribution. This can produce nulls of polarised intensity in an image, as potentially observed in AS 205.We discuss
the geometry and content of the systems by comparing the polarised light observations with other data at similar resolution,
namely with ALMA continuum and gas emission. Collective observational data can constrain the systems’ geometry and stellar
trajectories, with the important potential to differentiate between dynamical scenarios of stellar interaction.
Galaxy interactions are the dominant trigger for local type 2 quasarsSérgio Sacani
The triggering mechanism for the most luminous, quasar-like active galactic nuclei (AGN) remains a source of debate, with
some studies favouring triggering via galaxy mergers, but others finding little evidence to support this mechanism. Here, we
present deep Isaac Newton Telescope/Wide Field Camera imaging observations of a complete sample of 48 optically selected
type 2 quasars – the QSOFEED sample (L[O III] > 108.5 L; z < 0.14). Based on visual inspection by eight classifiers, we find
clear evidence that galaxy interactions are the dominant triggering mechanism for quasar activity in the local universe, with
65+6
−7 per cent of the type 2 quasar hosts showing morphological features consistent with galaxy mergers or encounters, compared
with only 22+5
−4 per cent of a stellar-mass- and redshift-matched comparison sample of non-AGN galaxies – a 5σ difference. The
type 2 quasar hosts are a factor of 3.0+0.5 −0.8 more likely to be morphologically disturbed than their matched non-AGN counterparts,
similar to our previous results for powerful 3CR radio AGN of comparable [O III] emission-line luminosity and redshift. In
contrast to the idea that quasars are triggered at the peaks of galaxy mergers as the two nuclei coalesce, and only become
visible post-coalescence, the majority of morphologically disturbed type 2 quasar sources in our sample are observed in the
pre-coalescence phase (61+8
−9 per cent). We argue that much of the apparent ambiguity that surrounds observational results in this
field is a result of differences in the surface brightness depths of the observations, combined with the effects of cosmological
surface brightness dimming.
The network of filaments with embedded clusters surrounding voids, which has been seen in maps derived from
redshift surveys and reproduced in simulations, has been referred to as the cosmic web. A complementary
description is provided by considering the shear in the velocity field of galaxies. The eigenvalues of the shear
provide information regarding whether or not a region is collapsing in three dimensions, which is the condition for
a knot, expanding in three dimensions, which is the condition for a void, or in the intermediate condition of a
filament or sheet. The structures that are quantitatively defined by the eigenvalues can be approximated by isocontours
that provide a visual representation of the cosmic velocity (V) web. The current application is based on
radial peculiar velocities from the Cosmicflows-2 collection of distances. The three-dimensional velocity field is
constructed using the Wiener filter methodology in the linear approximation. Eigenvalues of the velocity shear are
calculated at each point on a grid. Here, knots and filaments are visualized across a local domain of
diameter ~0.1c
Os astrônomos descobriram um processo único sobre como as maiores galáxias elípticas do universo continuam gerando estrelas muito tempo depois do anos de pico de nascimentos estelares. A alta resolução e a sensibilidade à radiação ultravioleta do Hubble, permitiu aos astrônomos observarem nós brilhantes de estrelas azuis, quentes, se formando juntamente com jatos de buracos negros ativos encontrados nos centros das gigantescas galáxias elípticas.
Combinando dados do Huubble com observações feitas por um conjunto de telescópios baseados tanto em Terra como no espaço, duas equipes independentes descobriram que os jatos dos buracos negros, e as estrelas recém-nascidas são todos partes de um ciclo auto-regulado. Jatos de alta energia atirados do buraco negro aquecem um halo de gás circulante, controlando a taxa com a qual o gás esfria e cai na galáxia.
“Pense no gás ao redor da galáxia como uma atmosfera”, explicou o líder do primeiro estudo, Megan Donahue, da Universidade Estadual do Michigan. “Essa atmosfera pode conter material em diferentes estados, do mesmo modo que a nossa atmosfera tem gás, nuvens e chuva. O que nós estamos vendo é um processo parecido com uma tempestade. À medida que os jatos impulsionam o gás para fora do centro da galáxia, parte do gás esfria e precipita em aglomerados frios que caem de volta para o centro da galáxia como gotas de chuvas”.
“As gotas de chuva eventualmente esfriam o suficiente para tornar-se nuvens de formação de estrelas de gás frio molecular, e a capacidade de observar no ultravioleta distante do Hubble, nos permitiu observar diretamente esses chuviscos de formação de estrelas”, explicou o líder do segundo estudo, Grant Tremblay, da Universidade de Yale. “Nós sabemos que esses chuviscos estão linkados com os jatos, pois eles foram encontrados em filamentos que se dobram ao redor dos jatos, ou abraçam as bordas de bolhas gigantes que os jatos inflaram”, disse Tremblay. “E eles terminam fazendo um redemoinho de gás de formação de estrelas ao redor do buraco negro central”.
Evidence for the_thermal_sunyaev-zeldovich_effect_associated_with_quasar_feed...Sérgio Sacani
Using a radio-quiet subsample of the Sloan Digital Sky Survey spectroscopic quasar
catalogue, spanning redshifts 0.5–3.5, we derive the mean millimetre and far-infrared
quasar spectral energy distributions (SEDs) via a stacking analysis of Atacama Cosmology
Telescope and Herschel-Spectral and Photometric Imaging REceiver data. We
constrain the form of the far-infrared emission and find 3σ–4σ evidence for the thermal
Sunyaev-Zel’dovich (SZ) effect, characteristic of a hot ionized gas component with
thermal energy (6.2 ± 1.7) × 1060 erg. This amount of thermal energy is greater than
expected assuming only hot gas in virial equilibrium with the dark matter haloes of
(1 − 5) × 1012h
−1M that these systems are expected to occupy, though the highest
quasar mass estimates found in the literature could explain a large fraction of this
energy. Our measurements are consistent with quasars depositing up to (14.5±3.3) τ
−1
8
per cent of their radiative energy into their circumgalactic environment if their typical
period of quasar activity is τ8 × 108 yr. For high quasar host masses, ∼ 1013h
−1M,
this percentage will be reduced. Furthermore, the uncertainty on this percentage is
only statistical and additional systematic uncertainties enter at the 40 per cent level.
The SEDs are dust dominated in all bands and we consider various models for dust
emission. While sufficiently complex dust models can obviate the SZ effect, the SZ
interpretation remains favoured at the 3σ–4σ level for most models.
This document summarizes evidence that submillimeter galaxies (SMGs) at redshift 3-6 may be progenitors of compact quiescent galaxies observed at redshift 2. It compares properties of a sample of z~2 quiescent galaxies with a statistical sample of z>3 SMGs in the COSMOS field. It finds that the formation redshifts of the z~2 galaxies match the observed redshift distribution of z>3 SMGs. It also finds that the space densities and properties such as sizes, stellar masses, and internal velocities of the two populations are consistent with an evolutionary connection, assuming SMG starbursts have a duty cycle of 42+40 Myr. This suggests SMGs may represent an early burst
Identification of Superclusters and Their Properties in the Sloan Digital Sky...Sérgio Sacani
Superclusters are the largest massive structures in the cosmic web, on tens to hundreds of megaparsec scales. They
are the largest assembly of galaxy clusters in the Universe. Apart from a few detailed studies of such structures,
their evolutionary mechanism is still an open question. In order to address and answer the relevant questions, a
statistically significant, large catalog of superclusters covering a wide range of redshifts and sky areas is essential.
Here, we present a large catalog of 662 superclusters identified using a modified friends-of-friends algorithm
applied on the WHL (Wen–Han–Liu) cluster catalog within a redshift range of 0.05 z 0.42. We name the most
massive supercluster at z ∼ 0.25 as the Einasto Supercluster. We find that the median mass of superclusters is
∼5.8 × 10 15 Me and the median size ∼65 Mpc. We find that the supercluster environment slightly affects the
growth of clusters. We compare the properties of the observed superclusters with the mock superclusters extracted
from the Horizon Run 4 cosmological simulation. The properties of the superclusters in the mocks and
observations are in broad agreement. We find that the density contrast of a supercluster is correlated with its
maximum extent with a power-law index, α ∼ −2. The phase-space distribution of mock superclusters shows that,
on average, ∼90% of part of a supercluster has a gravitational influence on its constituents. We also show the mock
halos’ average number density and peculiar velocity profiles in and around the superclusters.
Imaging the Milky Way with Millihertz Gravitational WavesSérgio Sacani
Modern astronomers enjoy access to all-sky images across a wide range of the electromagnetic spectrum from
long-wavelength radio to high-energy gamma rays. The most prominent feature in many of these images is our
own Galaxy, with different features revealed in each wave band. Gravitational waves (GWs) have recently been
added to the astronomers’ toolkit as a nonelectromagnetic messenger. To date, all identified GW sources have been
extra-Galactic and transient. However, the Milky Way hosts a population of ultracompact binaries (UCBs), which
radiate persistent GWs in the milliHertz band that is not observable with today’s terrestrial gravitational-wave
detectors. Space-based detectors such as the Laser Interferometer Space Antenna will measure this population and
provide a census of their location, masses, and orbital properties. In this work, we will show how this data can be
used to form a false-color image of the Galaxy that represents the intensity and frequency of the gravitational
waves produced by the UCB population. Such images can be used to study the morphology of the Galaxy, identify
interesting multimessenger sources through cross-matching, and for educational and outreach purposes.
The most luminous_galaxies_discovered_by_wiseSérgio Sacani
This document presents a sample of 20 extremely luminous galaxies discovered by the Wide-field Infrared Survey Explorer (WISE). Five of these galaxies have infrared luminosities exceeding 1014 solar luminosities, the highest infrared luminosity threshold yet observed. They were selected using criteria requiring weak or no detection in the first two WISE bands but strong detections in the third and fourth bands. Spectral energy distribution modeling suggests their high luminosities are powered by obscured active galactic nuclei with hot dust temperatures around 450 Kelvin. The existence of such luminous galaxies at redshifts above 3 provides constraints on the early growth of supermassive black holes through rapid accretion.
This document summarizes observations of the lensed galaxy HATLAS J142935.3-002836 (H1429-0028) from the Herschel-ATLAS survey. Optical spectroscopy revealed the foreground lens is at redshift 0.218, while the background galaxy is at redshift 1.027. High-resolution imaging from Hubble Space Telescope and Keck adaptive optics show the background galaxy is comprised of two components and a tidal tail, resembling a major merger. Analysis of ALMA observations of CO emission provides a dynamical mass estimate of one component as 5.8 ± 1.7 × 1010 M☉. Modeling of the spectral energy distribution indicates the total stellar mass is 1.32
The abundance of_x_shpoaed_radio_sources_implications_for_the_gravitational_w...Sérgio Sacani
Devem existir menos buracos negros supermassivos binários nos núcleos das galáxias do que se pensava anteriormente, disse uma equipe de cientistas da Universidade de Brandeis em Waltaham, Massachussets, e do Instituto de Pesquisa Raman em Bangalore, na Índia.
A maior parte das galáxias massivas no universo devem abrigar no mínimo um buraco negro supermassivo em seus núcleos.
Quando duas galáxias colidem, seus buracos negros se juntam, formando uma dança colossal que resulta numa combinação de par. Esse processo é a mais intensa fonte de ondas gravitacionais no universo, que ainda precisam ser diretamente detectadas.
“As ondas gravitacionais representam a próxima fronteira da astrofísica, e sua detecção levará a novas ideias sobre o universo. É importante se ter a maior quantidade de informação possível sobre as fontes dessas ondas”, disse o Dr. David Roberts, um membro da equipe da Universidade de Brandeis.
Dust in the_polar_region_as_a_major_contributor_to_the_infrared_emission_of_a...Sérgio Sacani
The mid-infrared emission of the active galactic nucleus NGC 3783 was observed using interferometry over multiple epochs, providing dense coverage of position angles and baselines. The emission was found to be strongly elongated along a position angle of -52 degrees, closely aligned with the polar axis orientation of -45 degrees. The half-light radii were measured to be 20.0 mas by 6.7 mas, corresponding to an axis ratio of 3:1. This implies that 60-90% of the 8-13 micron emission is from the polar-elongated component. The observations support a scenario where the majority of mid-infrared emission in Seyfert galaxies originates from a dusty wind in the polar region,
Is the atmosphere of the ultra-hot Jupiter WASP-121 b variable?Sérgio Sacani
We present a comprehensive analysis of the Hubble Space Telescope observations of the atmosphere
of WASP-121 b, a ultra-hot Jupiter. After reducing the transit, eclipse, and phase-curve observations
with a uniform methodology and addressing the biases from instrument systematics, sophisticated
atmospheric retrievals are used to extract robust constraints on the thermal structure, chemistry, and
cloud properties of the atmosphere. Our analysis shows that the observations are consistent with a
strong thermal inversion beginning at ∼104 Pa on the dayside, solar to subsolar metallicity Z (i.e.,
−0.77 < log(Z) < 0.05), and super-solar C/O ratio (i.e., 0.59 < C/O < 0.87). More importantly,
utilizing the high signal-to-noise ratio and repeated observations of the planet, we identify the following
unambiguous time-varying signals in the data: i) a shift of the putative hotspot offset between the
two phase-curves and ii) varying spectral signatures in the transits and eclipses. By simulating the
global dynamics of WASP-121 b atmosphere at high-resolution, we show that the identified signals are
consistent with quasi-periodic weather patterns, hence atmospheric variability, with signatures at the
level probed by the observations (∼5% to ∼10%) that change on a timescale of ∼5 planet days; in
the simulations, the weather patterns arise from the formation and movement of storms and fronts,
causing hot (as well as cold) patches of atmosphere to deform, separate, and mix in time.
A spectroscopic sample_of_massive_galaxiesSérgio Sacani
This document describes a study of 16 massive galaxies at z ~ 2 selected from the 3D-HST spectroscopic survey based on the detection of a strong 4000 Angstrom break in their spectra. Spectroscopy and imaging from HST/WFC3 are used to determine accurate redshifts, stellar population properties, and structural parameters. The sample significantly increases the number of spectroscopically confirmed evolved galaxies at z ~ 2 with robust size measurements. The analysis populates the mass-size relation and finds it is consistent with local relations but with smaller sizes by a factor of 2-3. A model is presented where the observed size evolution is explained by quenching of increasingly larger star-forming galaxies at a rate set by
DISCOVERY OF A GALAXY CLUSTER WITH A VIOLENTLY STARBURSTING CORE AT z = 2:506Sérgio Sacani
We report the discovery of a remarkable concentration of massive galaxies with extended X-ray
emission at zspec = 2:506, which contains 11 massive (M & 1011M) galaxies in the central 80kpc
region (11.6 overdensity). We have spectroscopically conrmed 17 member galaxies with 11 from CO
and the remaining ones from H. The X-ray luminosity, stellar mass content and velocity dispersion
all point to a collapsed, cluster-sized dark matter halo with mass M200c = 1013:90:2M, making it
the most distant X-ray-detected cluster known to date. Unlike other clusters discovered so far, this
structure is dominated by star-forming galaxies (SFGs) in the core with only 2 out of the 11 massive
galaxies classied as quiescent. The star formation rate (SFR) in the 80kpc core reaches 3400 M
yr 1 with a gas depletion time of 200 Myr, suggesting that we caught this cluster in rapid build-up
of a dense core. The high SFR is driven by both a high abundance of SFGs and a higher starburst
fraction ( 25%, compared to 3%-5% in the eld). The presence of both a collapsed, cluster-sized
halo and a predominant population of massive SFGs suggests that this structure could represent an
important transition phase between protoclusters and mature clusters. It provides evidence that the
main phase of massive galaxy passivization will take place after galaxies accrete onto the cluster,
providing new insights into massive cluster formation at early epochs. The large integrated stellar
mass at such high redshift challenges our understanding of massive cluster formation.
A giant ring_like_structure_at_078_z_086_displayed_by_gr_bsSérgio Sacani
This document describes the discovery of a giant ring-like structure in the observable universe displayed by 9 gamma ray bursts (GRBs) between redshifts of 0.78 and 0.86. The ring has a diameter of 1720 Mpc, over five times larger than the expected transition scale to homogeneity. The ring lies at a distance of 2770 Mpc with major and minor diameters of 43° and 30°, respectively. The probability of this structure occurring by random chance is calculated to be 2 × 10-6. This ring-shaped feature contradicts the cosmological principle of large-scale homogeneity and isotropy, and the physical mechanism responsible is unknown.
The galaxy morphology–density relation in the EAGLE simulationSérgio Sacani
This study uses a convolutional neural network trained on observed galaxy images to classify galaxies in the EAGLE cosmological hydrodynamical simulation by visual morphology. It finds that EAGLE reproduces both the observed relationships between galaxy morphology and local density (the morphology-density relation), and between morphology and galaxy mass. Through analysis of the simulations, the key processes identified as driving the morphology-density relation are: (1) the transformation of disc galaxies into lenticular galaxies via gas stripping in dense environments, (2) the formation of lenticular galaxies through merger-induced black hole feedback in less dense environments, and (3) the increasing fraction of more elliptical, high-mass galaxies at higher densities.
Storm in teacup_a_radio_quiet_quasar_with_radio_emitting_bubblesSérgio Sacani
Artigo descreve descoberta feita com o VLA de uma tempestade nas ondas de rádio em uma galáxia até então calma, o que traz conclusões sobre a evolução das galáxias.
A High-mass, Young Star-forming Core Escaping from Its Parental FilamentSérgio Sacani
We studied the unique kinematic properties in massive filament G352.63-1.07 at 103 au spatial scale with the dense
molecular tracers observed with the Atacama Large Millimeter/submillimeter Array. We find the central massive
core M1 (12 Me) being separated from the surrounding filament with a velocity difference of
- =- - v vsys 2 km s 1 and a transverse separation within 3″. Meanwhile, as shown in multiple dense-gas
tracers, M1 has a spatial extension closely aligned with the main filament and is connected to the filament toward
both its ends. M1 thus represents a very beginning state for a massive, young star-forming core escaping from the
parental filament, within a timescale of ∼4000 yr. Based on its kinetic energy (3.5 × 1044 erg), the core escape is
unlikely solely due to the original filament motion or magnetic field but requires more energetic events such as a
rapid intense anisotropic collapse. The released energy also seems to noticeably increase the environmental
turbulence. This may help the filament to become stabilized again.
Similar to Jet reorientation in central galaxies of clusters and groups: insights from VLBA and Chandra data (20)
The binding of cosmological structures by massless topological defectsSérgio Sacani
Assuming spherical symmetry and weak field, it is shown that if one solves the Poisson equation or the Einstein field
equations sourced by a topological defect, i.e. a singularity of a very specific form, the result is a localized gravitational
field capable of driving flat rotation (i.e. Keplerian circular orbits at a constant speed for all radii) of test masses on a thin
spherical shell without any underlying mass. Moreover, a large-scale structure which exploits this solution by assembling
concentrically a number of such topological defects can establish a flat stellar or galactic rotation curve, and can also deflect
light in the same manner as an equipotential (isothermal) sphere. Thus, the need for dark matter or modified gravity theory is
mitigated, at least in part.
EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Weste...Sérgio Sacani
Context. With a mass exceeding several 104 M⊙ and a rich and dense population of massive stars, supermassive young star clusters
represent the most massive star-forming environment that is dominated by the feedback from massive stars and gravitational interactions
among stars.
Aims. In this paper we present the Extended Westerlund 1 and 2 Open Clusters Survey (EWOCS) project, which aims to investigate
the influence of the starburst environment on the formation of stars and planets, and on the evolution of both low and high mass stars.
The primary targets of this project are Westerlund 1 and 2, the closest supermassive star clusters to the Sun.
Methods. The project is based primarily on recent observations conducted with the Chandra and JWST observatories. Specifically,
the Chandra survey of Westerlund 1 consists of 36 new ACIS-I observations, nearly co-pointed, for a total exposure time of 1 Msec.
Additionally, we included 8 archival Chandra/ACIS-S observations. This paper presents the resulting catalog of X-ray sources within
and around Westerlund 1. Sources were detected by combining various existing methods, and photon extraction and source validation
were carried out using the ACIS-Extract software.
Results. The EWOCS X-ray catalog comprises 5963 validated sources out of the 9420 initially provided to ACIS-Extract, reaching a
photon flux threshold of approximately 2 × 10−8 photons cm−2
s
−1
. The X-ray sources exhibit a highly concentrated spatial distribution,
with 1075 sources located within the central 1 arcmin. We have successfully detected X-ray emissions from 126 out of the 166 known
massive stars of the cluster, and we have collected over 71 000 photons from the magnetar CXO J164710.20-455217.
The debris of the ‘last major merger’ is dynamically youngSérgio Sacani
The Milky Way’s (MW) inner stellar halo contains an [Fe/H]-rich component with highly eccentric orbits, often referred to as the
‘last major merger.’ Hypotheses for the origin of this component include Gaia-Sausage/Enceladus (GSE), where the progenitor
collided with the MW proto-disc 8–11 Gyr ago, and the Virgo Radial Merger (VRM), where the progenitor collided with the
MW disc within the last 3 Gyr. These two scenarios make different predictions about observable structure in local phase space,
because the morphology of debris depends on how long it has had to phase mix. The recently identified phase-space folds in Gaia
DR3 have positive caustic velocities, making them fundamentally different than the phase-mixed chevrons found in simulations
at late times. Roughly 20 per cent of the stars in the prograde local stellar halo are associated with the observed caustics. Based
on a simple phase-mixing model, the observed number of caustics are consistent with a merger that occurred 1–2 Gyr ago.
We also compare the observed phase-space distribution to FIRE-2 Latte simulations of GSE-like mergers, using a quantitative
measurement of phase mixing (2D causticality). The observed local phase-space distribution best matches the simulated data
1–2 Gyr after collision, and certainly not later than 3 Gyr. This is further evidence that the progenitor of the ‘last major merger’
did not collide with the MW proto-disc at early times, as is thought for the GSE, but instead collided with the MW disc within
the last few Gyr, consistent with the body of work surrounding the VRM.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
Multi-source connectivity as the driver of solar wind variability in the heli...Sérgio Sacani
The ambient solar wind that flls the heliosphere originates from multiple
sources in the solar corona and is highly structured. It is often described
as high-speed, relatively homogeneous, plasma streams from coronal
holes and slow-speed, highly variable, streams whose source regions are
under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify
solar wind sources and understand what drives the complexity seen in the
heliosphere. By combining magnetic feld modelling and spectroscopic
techniques with high-resolution observations and measurements, we show
that the solar wind variability detected in situ by Solar Orbiter in March
2022 is driven by spatio-temporal changes in the magnetic connectivity to
multiple sources in the solar atmosphere. The magnetic feld footpoints
connected to the spacecraft moved from the boundaries of a coronal hole
to one active region (12961) and then across to another region (12957). This
is refected in the in situ measurements, which show the transition from fast
to highly Alfvénic then to slow solar wind that is disrupted by the arrival of
a coronal mass ejection. Our results describe solar wind variability at 0.5 au
but are applicable to near-Earth observatories.
Gliese 12 b: A Temperate Earth-sized Planet at 12 pc Ideal for Atmospheric Tr...Sérgio Sacani
Recent discoveries of Earth-sized planets transiting nearby M dwarfs have made it possible to characterize the
atmospheres of terrestrial planets via follow-up spectroscopic observations. However, the number of such planets
receiving low insolation is still small, limiting our ability to understand the diversity of the atmospheric
composition and climates of temperate terrestrial planets. We report the discovery of an Earth-sized planet
transiting the nearby (12 pc) inactive M3.0 dwarf Gliese 12 (TOI-6251) with an orbital period (Porb) of 12.76 days.
The planet, Gliese 12 b, was initially identified as a candidate with an ambiguous Porb from TESS data. We
confirmed the transit signal and Porb using ground-based photometry with MuSCAT2 and MuSCAT3, and
validated the planetary nature of the signal using high-resolution images from Gemini/NIRI and Keck/NIRC2 as
well as radial velocity (RV) measurements from the InfraRed Doppler instrument on the Subaru 8.2 m telescope
and from CARMENES on the CAHA 3.5 m telescope. X-ray observations with XMM-Newton showed the host
star is inactive, with an X-ray-to-bolometric luminosity ratio of log 5.7 L L X bol » - . Joint analysis of the light
curves and RV measurements revealed that Gliese 12 b has a radius of 0.96 ± 0.05 R⊕,a3σ mass upper limit of
3.9 M⊕, and an equilibrium temperature of 315 ± 6 K assuming zero albedo. The transmission spectroscopy metric
(TSM) value of Gliese 12 b is close to the TSM values of the TRAPPIST-1 planets, adding Gliese 12 b to the small
list of potentially terrestrial, temperate planets amenable to atmospheric characterization with JWST.
Gliese 12 b, a temperate Earth-sized planet at 12 parsecs discovered with TES...Sérgio Sacani
We report on the discovery of Gliese 12 b, the nearest transiting temperate, Earth-sized planet found to date. Gliese 12 is a
bright (V = 12.6 mag, K = 7.8 mag) metal-poor M4V star only 12.162 ± 0.005 pc away from the Solar system with one of the
lowest stellar activity levels known for M-dwarfs. A planet candidate was detected by TESS based on only 3 transits in sectors
42, 43, and 57, with an ambiguity in the orbital period due to observational gaps. We performed follow-up transit observations
with CHEOPS and ground-based photometry with MINERVA-Australis, SPECULOOS, and Purple Mountain Observatory,
as well as further TESS observations in sector 70. We statistically validate Gliese 12 b as a planet with an orbital period of
12.76144 ± 0.00006 d and a radius of 1.0 ± 0.1 R⊕, resulting in an equilibrium temperature of ∼315 K. Gliese 12 b has excellent
future prospects for precise mass measurement, which may inform how planetary internal structure is affected by the stellar
compositional environment. Gliese 12 b also represents one of the best targets to study whether Earth-like planets orbiting cool
stars can retain their atmospheres, a crucial step to advance our understanding of habitability on Earth and across the galaxy.
The importance of continents, oceans and plate tectonics for the evolution of...Sérgio Sacani
Within the uncertainties of involved astronomical and biological parameters, the Drake Equation
typically predicts that there should be many exoplanets in our galaxy hosting active, communicative
civilizations (ACCs). These optimistic calculations are however not supported by evidence, which is
often referred to as the Fermi Paradox. Here, we elaborate on this long-standing enigma by showing
the importance of planetary tectonic style for biological evolution. We summarize growing evidence
that a prolonged transition from Mesoproterozoic active single lid tectonics (1.6 to 1.0 Ga) to modern
plate tectonics occurred in the Neoproterozoic Era (1.0 to 0.541 Ga), which dramatically accelerated
emergence and evolution of complex species. We further suggest that both continents and oceans
are required for ACCs because early evolution of simple life must happen in water but late evolution
of advanced life capable of creating technology must happen on land. We resolve the Fermi Paradox
(1) by adding two additional terms to the Drake Equation: foc
(the fraction of habitable exoplanets
with significant continents and oceans) and fpt
(the fraction of habitable exoplanets with significant
continents and oceans that have had plate tectonics operating for at least 0.5 Ga); and (2) by
demonstrating that the product of foc
and fpt
is very small (< 0.00003–0.002). We propose that the lack
of evidence for ACCs reflects the scarcity of long-lived plate tectonics and/or continents and oceans on
exoplanets with primitive life.
A Giant Impact Origin for the First Subduction on EarthSérgio Sacani
Hadean zircons provide a potential record of Earth's earliest subduction 4.3 billion years ago. Itremains enigmatic how subduction could be initiated so soon after the presumably Moon‐forming giant impact(MGI). Earlier studies found an increase in Earth's core‐mantle boundary (CMB) temperature due to theaccumulation of the impactor's core, and our recent work shows Earth's lower mantle remains largely solid, withsome of the impactor's mantle potentially surviving as the large low‐shear velocity provinces (LLSVPs). Here,we show that a hot post‐impact CMB drives the initiation of strong mantle plumes that can induce subductioninitiation ∼200 Myr after the MGI. 2D and 3D thermomechanical computations show that a high CMBtemperature is the primary factor triggering early subduction, with enrichment of heat‐producing elements inLLSVPs as another potential factor. The models link the earliest subduction to the MGI with implications forunderstanding the diverse tectonic regimes of rocky planets.
Climate extremes likely to drive land mammal extinction during next supercont...Sérgio Sacani
Mammals have dominated Earth for approximately 55 Myr thanks to their
adaptations and resilience to warming and cooling during the Cenozoic. All
life will eventually perish in a runaway greenhouse once absorbed solar
radiation exceeds the emission of thermal radiation in several billions of
years. However, conditions rendering the Earth naturally inhospitable to
mammals may develop sooner because of long-term processes linked to
plate tectonics (short-term perturbations are not considered here). In
~250 Myr, all continents will converge to form Earth’s next supercontinent,
Pangea Ultima. A natural consequence of the creation and decay of Pangea
Ultima will be extremes in pCO2 due to changes in volcanic rifting and
outgassing. Here we show that increased pCO2, solar energy (F⨀;
approximately +2.5% W m−2 greater than today) and continentality (larger
range in temperatures away from the ocean) lead to increasing warming
hostile to mammalian life. We assess their impact on mammalian
physiological limits (dry bulb, wet bulb and Humidex heat stress indicators)
as well as a planetary habitability index. Given mammals’ continued survival,
predicted background pCO2 levels of 410–816 ppm combined with increased
F⨀ will probably lead to a climate tipping point and their mass extinction.
The results also highlight how global landmass configuration, pCO2 and F⨀
play a critical role in planetary habitability.
Constraints on Neutrino Natal Kicks from Black-Hole Binary VFTS 243Sérgio Sacani
The recently reported observation of VFTS 243 is the first example of a massive black-hole binary
system with negligible binary interaction following black-hole formation. The black-hole mass (≈10M⊙)
and near-circular orbit (e ≈ 0.02) of VFTS 243 suggest that the progenitor star experienced complete
collapse, with energy-momentum being lost predominantly through neutrinos. VFTS 243 enables us to
constrain the natal kick and neutrino-emission asymmetry during black-hole formation. At 68% confidence
level, the natal kick velocity (mass decrement) is ≲10 km=s (≲1.0M⊙), with a full probability distribution
that peaks when ≈0.3M⊙ were ejected, presumably in neutrinos, and the black hole experienced a natal
kick of 4 km=s. The neutrino-emission asymmetry is ≲4%, with best fit values of ∼0–0.2%. Such a small
neutrino natal kick accompanying black-hole formation is in agreement with theoretical predictions.
Detectability of Solar Panels as a TechnosignatureSérgio Sacani
In this work, we assess the potential detectability of solar panels made of silicon on an Earth-like
exoplanet as a potential technosignature. Silicon-based photovoltaic cells have high reflectance in the
UV-VIS and in the near-IR, within the wavelength range of a space-based flagship mission concept
like the Habitable Worlds Observatory (HWO). Assuming that only solar energy is used to provide
the 2022 human energy needs with a land cover of ∼ 2.4%, and projecting the future energy demand
assuming various growth-rate scenarios, we assess the detectability with an 8 m HWO-like telescope.
Assuming the most favorable viewing orientation, and focusing on the strong absorption edge in the
ultraviolet-to-visible (0.34 − 0.52 µm), we find that several 100s of hours of observation time is needed
to reach a SNR of 5 for an Earth-like planet around a Sun-like star at 10pc, even with a solar panel
coverage of ∼ 23% land coverage of a future Earth. We discuss the necessity of concepts like Kardeshev
Type I/II civilizations and Dyson spheres, which would aim to harness vast amounts of energy. Even
with much larger populations than today, the total energy use of human civilization would be orders of
magnitude below the threshold for causing direct thermal heating or reaching the scale of a Kardashev
Type I civilization. Any extraterrrestrial civilization that likewise achieves sustainable population
levels may also find a limit on its need to expand, which suggests that a galaxy-spanning civilization
as imagined in the Fermi paradox may not exist.
The solar dynamo begins near the surfaceSérgio Sacani
The magnetic dynamo cycle of the Sun features a distinct pattern: a propagating
region of sunspot emergence appears around 30° latitude and vanishes near the
equator every 11 years (ref. 1). Moreover, longitudinal flows called torsional oscillations
closely shadow sunspot migration, undoubtedly sharing a common cause2. Contrary
to theories suggesting deep origins of these phenomena, helioseismology pinpoints
low-latitude torsional oscillations to the outer 5–10% of the Sun, the near-surface
shear layer3,4. Within this zone, inwardly increasing differential rotation coupled with
a poloidal magnetic field strongly implicates the magneto-rotational instability5,6,
prominent in accretion-disk theory and observed in laboratory experiments7.
Together, these two facts prompt the general question: whether the solar dynamo is
possibly a near-surface instability. Here we report strong affirmative evidence in stark
contrast to traditional models8 focusing on the deeper tachocline. Simple analytic
estimates show that the near-surface magneto-rotational instability better explains
the spatiotemporal scales of the torsional oscillations and inferred subsurface
magnetic field amplitudes9. State-of-the-art numerical simulations corroborate these
estimates and reproduce hemispherical magnetic current helicity laws10. The dynamo
resulting from a well-understood near-surface phenomenon improves prospects
for accurate predictions of full magnetic cycles and space weather, affecting the
electromagnetic infrastructure of Earth.
Extensive Pollution of Uranus and Neptune’s Atmospheres by Upsweep of Icy Mat...Sérgio Sacani
In the Nice model of solar system formation, Uranus and Neptune undergo an orbital upheaval,
sweeping through a planetesimal disk. The region of the disk from which material is accreted by
the ice giants during this phase of their evolution has not previously been identified. We perform
direct N-body orbital simulations of the four giant planets to determine the amount and origin of solid
accretion during this orbital upheaval. We find that the ice giants undergo an extreme bombardment
event, with collision rates as much as ∼3 per hour assuming km-sized planetesimals, increasing the
total planet mass by up to ∼0.35%. In all cases, the initially outermost ice giant experiences the
largest total enhancement. We determine that for some plausible planetesimal properties, the resulting
atmospheric enrichment could potentially produce sufficient latent heat to alter the planetary cooling
timescale according to existing models. Our findings suggest that substantial accretion during this
phase of planetary evolution may have been sufficient to impact the atmospheric composition and
thermal evolution of the ice giants, motivating future work on the fate of deposited solid material.
Exomoons & Exorings with the Habitable Worlds Observatory I: On the Detection...Sérgio Sacani
The highest priority recommendation of the Astro2020 Decadal Survey for space-based astronomy
was the construction of an observatory capable of characterizing habitable worlds. In this paper series
we explore the detectability of and interference from exomoons and exorings serendipitously observed
with the proposed Habitable Worlds Observatory (HWO) as it seeks to characterize exoplanets, starting
in this manuscript with Earth-Moon analog mutual events. Unlike transits, which only occur in systems
viewed near edge-on, shadow (i.e., solar eclipse) and lunar eclipse mutual events occur in almost every
star-planet-moon system. The cadence of these events can vary widely from ∼yearly to multiple events
per day, as was the case in our younger Earth-Moon system. Leveraging previous space-based (EPOXI)
lightcurves of a Moon transit and performance predictions from the LUVOIR-B concept, we derive
the detectability of Moon analogs with HWO. We determine that Earth-Moon analogs are detectable
with observation of ∼2-20 mutual events for systems within 10 pc, and larger moons should remain
detectable out to 20 pc. We explore the extent to which exomoon mutual events can mimic planet
features and weather. We find that HWO wavelength coverage in the near-IR, specifically in the 1.4 µm
water band where large moons can outshine their host planet, will aid in differentiating exomoon signals
from exoplanet variability. Finally, we predict that exomoons formed through collision processes akin
to our Moon are more likely to be detected in younger systems, where shorter orbital periods and
favorable geometry enhance the probability and frequency of mutual events.
Emergent ribozyme behaviors in oxychlorine brines indicate a unique niche for...Sérgio Sacani
Mars is a particularly attractive candidate among known astronomical objects
to potentially host life. Results from space exploration missions have provided
insights into Martian geochemistry that indicate oxychlorine species, particularly perchlorate, are ubiquitous features of the Martian geochemical landscape. Perchlorate presents potential obstacles for known forms of life due to
its toxicity. However, it can also provide potential benefits, such as producing
brines by deliquescence, like those thought to exist on present-day Mars. Here
we show perchlorate brines support folding and catalysis of functional RNAs,
while inactivating representative protein enzymes. Additionally, we show
perchlorate and other oxychlorine species enable ribozyme functions,
including homeostasis-like regulatory behavior and ribozyme-catalyzed
chlorination of organic molecules. We suggest nucleic acids are uniquely wellsuited to hypersaline Martian environments. Furthermore, Martian near- or
subsurface oxychlorine brines, and brines found in potential lifeforms, could
provide a unique niche for biomolecular evolution.
Continuum emission from within the plunging region of black hole discsSérgio Sacani
The thermal continuum emission observed from accreting black holes across X-ray bands has the potential to be leveraged as a
powerful probe of the mass and spin of the central black hole. The vast majority of existing ‘continuum fitting’ models neglect
emission sourced at and within the innermost stable circular orbit (ISCO) of the black hole. Numerical simulations, however,
find non-zero emission sourced from these regions. In this work, we extend existing techniques by including the emission
sourced from within the plunging region, utilizing new analytical models that reproduce the properties of numerical accretion
simulations. We show that in general the neglected intra-ISCO emission produces a hot-and-small quasi-blackbody component,
but can also produce a weak power-law tail for more extreme parameter regions. A similar hot-and-small blackbody component
has been added in by hand in an ad hoc manner to previous analyses of X-ray binary spectra. We show that the X-ray spectrum
of MAXI J1820+070 in a soft-state outburst is extremely well described by a full Kerr black hole disc, while conventional
models that neglect intra-ISCO emission are unable to reproduce the data. We believe this represents the first robust detection of
intra-ISCO emission in the literature, and allows additional constraints to be placed on the MAXI J1820 + 070 black hole spin
which must be low a• < 0.5 to allow a detectable intra-ISCO region. Emission from within the ISCO is the dominant emission
component in the MAXI J1820 + 070 spectrum between 6 and 10 keV, highlighting the necessity of including this region. Our
continuum fitting model is made publicly available.
WASP-69b’s Escaping Envelope Is Confined to a Tail Extending at Least 7 RpSérgio Sacani
Studying the escaping atmospheres of highly irradiated exoplanets is critical for understanding the physical
mechanisms that shape the demographics of close-in planets. A number of planetary outflows have been observed
as excess H/He absorption during/after transit. Such an outflow has been observed for WASP-69b by multiple
groups that disagree on the geometry and velocity structure of the outflow. Here, we report the detection of this
planet’s outflow using Keck/NIRSPEC for the first time. We observed the outflow 1.28 hr after egress until the
target set, demonstrating the outflow extends at least 5.8 × 105 km or 7.5 Rp This detection is significantly longer
than previous observations, which report an outflow extending ∼2.2 planet radii just 1 yr prior. The outflow is
blueshifted by −23 km s−1 in the planetary rest frame. We estimate a current mass-loss rate of 1 M⊕ Gyr−1
. Our
observations are most consistent with an outflow that is strongly sculpted by ram pressure from the stellar wind.
However, potential variability in the outflow could be due to time-varying interactions with the stellar wind or
differences in instrumental precision.
When I was asked to give a companion lecture in support of ‘The Philosophy of Science’ (https://shorturl.at/4pUXz) I decided not to walk through the detail of the many methodologies in order of use. Instead, I chose to employ a long standing, and ongoing, scientific development as an exemplar. And so, I chose the ever evolving story of Thermodynamics as a scientific investigation at its best.
Conducted over a period of >200 years, Thermodynamics R&D, and application, benefitted from the highest levels of professionalism, collaboration, and technical thoroughness. New layers of application, methodology, and practice were made possible by the progressive advance of technology. In turn, this has seen measurement and modelling accuracy continually improved at a micro and macro level.
Perhaps most importantly, Thermodynamics rapidly became a primary tool in the advance of applied science/engineering/technology, spanning micro-tech, to aerospace and cosmology. I can think of no better a story to illustrate the breadth of scientific methodologies and applications at their best.
The cost of acquiring information by natural selectionCarl Bergstrom
This is a short talk that I gave at the Banff International Research Station workshop on Modeling and Theory in Population Biology. The idea is to try to understand how the burden of natural selection relates to the amount of information that selection puts into the genome.
It's based on the first part of this research paper:
The cost of information acquisition by natural selection
Ryan Seamus McGee, Olivia Kosterlitz, Artem Kaznatcheev, Benjamin Kerr, Carl T. Bergstrom
bioRxiv 2022.07.02.498577; doi: https://doi.org/10.1101/2022.07.02.498577
(June 12, 2024) Webinar: Development of PET theranostics targeting the molecu...Scintica Instrumentation
Targeting Hsp90 and its pathogen Orthologs with Tethered Inhibitors as a Diagnostic and Therapeutic Strategy for cancer and infectious diseases with Dr. Timothy Haystead.
ESA/ACT Science Coffee: Diego Blas - Gravitational wave detection with orbita...Advanced-Concepts-Team
Presentation in the Science Coffee of the Advanced Concepts Team of the European Space Agency on the 07.06.2024.
Speaker: Diego Blas (IFAE/ICREA)
Title: Gravitational wave detection with orbital motion of Moon and artificial
Abstract:
In this talk I will describe some recent ideas to find gravitational waves from supermassive black holes or of primordial origin by studying their secular effect on the orbital motion of the Moon or satellites that are laser ranged.
PPT on Direct Seeded Rice presented at the three-day 'Training and Validation Workshop on Modules of Climate Smart Agriculture (CSA) Technologies in South Asia' workshop on April 22, 2024.
aziz sancar nobel prize winner: from mardin to nobel
Jet reorientation in central galaxies of clusters and groups: insights from VLBA and Chandra data
1. Draft version December 6, 2023
Typeset using L
A
TEX twocolumn style in AASTeX631
Jet reorientation in central galaxies of clusters and groups: insights from VLBA and Chandra data
Francesco Ubertosi ,1, 2
Gerrit Schellenberger ,3
Ewan O’Sullivan ,3
Jan Vrtilek ,3
Simona Giacintucci ,4
Laurence P. David,3
William Forman ,3
Myriam Gitti ,1, 5
Tiziana Venturi ,5
Christine Jones,3
and Fabrizio Brighenti 1, 6
1Dipartimento di Fisica e Astronomia, Università di Bologna, via Gobetti 93/2, I-40129 Bologna, Italy
2Istituto Nazionale di Astrofisica - Osservatorio di Astrofisica e Scienza dello Spazio (OAS), via Gobetti 101, I-40129 Bologna, Italy
3Center for Astrophysics | Harvard & Smithsonian, 60 Garden Street, Cambridge, MA 02138, USA
4Naval Research Laboratory, 4555 Overlook Avenue SW, Code 7213, Washington, DC 20375, USA
5Istituto Nazionale di Astrofisica - Istituto di Radioastronomia (IRA), via Gobetti 101, I-40129 Bologna, Italy
6University of California Observatories/Lick Observatory, Department of Astronomy and Astrophysics, Santa Cruz, CA 95064, USA
(Received August 29, 2023; Accepted December 3, 2023)
ABSTRACT
Recent observations of galaxy clusters and groups with misalignments between their central AGN jets
and X-ray cavities, or with multiple misaligned cavities, have raised concerns about the jet – bubble
connection in cooling cores, and the processes responsible for jet realignment. To investigate the
frequency and causes of such misalignments, we construct a sample of 16 cool core galaxy clusters and
groups. Using VLBA radio data we measure the parsec-scale position angle of the jets, and compare
it with the position angle of the X-ray cavities detected in Chandra data. Using the overall sample
and selected subsets, we consistently find that there is a 30% – 38% chance to find a misalignment
larger than ∆Ψ = 45◦
when observing a cluster/group with a detected jet and at least one cavity. We
determine that projection may account for an apparently large ∆Ψ only in a fraction of objects (∼35%),
and given that gas dynamical disturbances (as sloshing) are found in both aligned and misaligned
systems, we exclude environmental perturbation as the main driver of cavity – jet misalignment.
Moreover, we find that large misalignments (up to ∼ 90◦
) are favored over smaller ones (45◦
≤ ∆Ψ ≤
70◦
), and that the change in jet direction can occur on timescales between one and a few tens of Myr.
We conclude that misalignments are more likely related to actual reorientation of the jet axis, and we
discuss several engine-based mechanisms that may cause these dramatic changes.
1. INTRODUCTION
In the context of groups and clusters of galaxies in
the local Universe, it is now clear that the co-evolution
of supermassive black holes (SMBH) and their envi-
ronment is regulated by a feedback mechanism. Gas,
cooling out of the hot intracluster/intragroup medium
(ICM/IGrM), fuels the central active galactic nucleus
(AGN), that in turn drives jets and outflows propagating
to tens or hundreds of kpc. These outbursts can pierce
and mechanically heat the surrounding gas, thereby
delaying further cooling (e.g., for reviews Mathews &
Brighenti 2003; McNamara & Nulsen 2007; Fabian 2012;
Corresponding author: Francesco Ubertosi
francesco.ubertosi2@unibo.it
Gitti et al. 2012; McNamara & Nulsen 2012; Werner
et al. 2019; Eckert et al. 2021; Donahue & Voit 2022).
The clearest footprints of jet activity on the ICM/IGrM
are X-ray-void bubbles (or cavities) inflated in the gas
by the expanding jet plasma, which can remain visible
in X-ray observations for tens of Myr after the outburst
began (e.g., Churazov et al. 2000; Wise et al. 2007; Gitti
et al. 2010; O’Sullivan et al. 2011; Randall et al. 2015;
Giacintucci et al. 2020; Ubertosi et al. 2021; Schellen-
berger et al. 2023).
The observation and investigation of X-ray cavities in
clusters and groups highlights several characteristics of
SMBH activity. First, the presence of multiple bubbles
in the cluster or group reflects the transitory and repet-
itive nature of radio activity in central galaxies. Many
systems have several pairs of cavities at increasing dis-
tance from the center (from a few kpc to ∼ 102
kpc),
arXiv:2312.02283v1
[astro-ph.GA]
4
Dec
2023
2. 2
with each pair related to a jet episode that lasted around
107
yr (e.g., Bı̂rzan et al. 2004; Fabian et al. 2005; Dunn
et al. 2005; Wise et al. 2007; Babul et al. 2013; Hlavacek-
Larrondo et al. 2015; Randall et al. 2015; Biava et al.
2021). The multiple bubbles are evidence for successive
jet – ICM/IGrM interactions, providing valuable infor-
mation on the duty cycle and mechanical energy of AGN
in dense environments.
Second, the AGN activity is directional. While the
mechanical energy can be distributed in every direc-
tion (through e.g. cocoon shock fronts, see Brighenti &
Mathews 2006; Huško et al. 2022, or internal waves gen-
erated by the buoyant cavities, see Zhang et al. 2019),
the bipolar jets that deposited such energy were driven
in specific and opposite directions from the SMBH. In
this context, in the absence of other effects, the posi-
tion of bubbles in the cluster or group atmosphere maps
the direction of the corresponding radio jets. In sev-
eral cases, older and younger pairs of X-ray cavities are
aligned along a common axis, suggesting that the jet has
been pointing in a similar direction over time (e.g., Wise
et al. 2007; Randall et al. 2015). However, observations
of objects with jets pointing to a very different direction
than the cavity location, or with multiple X-ray cavities
spread over the whole azimuth, support the idea that
the jet axis can also change its orientation over time
(e.g., Falceta-Gonçalves et al. 2010; Chon et al. 2012;
Babul et al. 2013; Schellenberger et al. 2021; Ubertosi
et al. 2021). Since the connection between the AGN jets
and the X-ray cavities is vital to support the idea of an
AGN feedback mechanism, several scenarios have been
investigated to understand the cause behind these dra-
matic misalignments.
Many possibilities are related to the physics of the
SMBH and the conditions of the innermost parsecs of
the central galaxy. Intervening obstacles or strong mag-
netic fields could bend or deflect the jets and change
their direction over time (McKinney et al. 2013; Morris
et al. 2022). A periodic precession of the jet axis, pos-
sibly caused by the jet-accretion disk interaction, may
also cause successive outbursts to appear rotated (Liska
et al. 2018; Lalakos et al. 2022; Huško et al. 2022). Alter-
natively, binary SMBH could explain both a progressive
change in the jets axis, due to the interaction between
the active SMBH and the orbiting one, and the exis-
tence of multiple jets and cavities in different directions,
if both SMBHs are active (e.g., Hudson et al. 2006; Ru-
binur et al. 2018; Ubertosi et al. 2021). Verifying these
possibilities is non-trivial, as the involved spatial scales
can be beyond the reach of radio observations.
Another possibility is that projection effects can cause
a large apparent offset, while the actual misalignment
between jets and cavity direction is small (see Singal
2016; Schellenberger et al. 2021). This explanation may
alleviate the difference in relative position of jets and
cavities observed in a fraction of systems.
Ultimately, environmental effects might play a major
role. Dynamical disturbances can trigger sloshing mo-
tions of the hot gas, that oscillates in the potential
well of the host cluster or group. Investigations of
these motions and X-ray cavities revealed that slosh-
ing may move X-ray cavities around the cluster atmo-
sphere (e.g., Falceta-Gonçalves et al. 2010; Randall et al.
2010; Paterno-Mahler et al. 2013; Kolokythas et al. 2020;
ZuHone et al. 2021), potentially perturbing the bubble
motion away from the original axis of the radio jets.
As feedback models rely on the central AGN to balance
cooling, the observations of jets, in cool core clusters and
groups, misaligned with the X-ray cavities has raised
concerns on the connection between the direct evidence
(the jets) and the smoking gun (the X-ray cavities) of
feedback. Such concerns have typically been addressed
by focusing on single peculiar objects, but it is essential
to analyze a larger sample of clusters and groups to pro-
vide a broader picture.
In this work we present the investigation of jets and X-
ray cavity alignment using a sample of galaxy clusters
and groups, to assess the relative importance of pro-
jection and environmental effects, to evaluate how rare
these misalignments are, and to gain new insights on the
mechanism through which AGN jets change direction
over time. Combining Chandra and Very Long Base-
line Array (VLBA) data, we observationally address the
alignment of X-ray cavities (on kpc scales) and radio jets
(on pc scales).
This paper is organized as follows. Section 2 presents
the criteria for the sample selection; Section 3 and 4 de-
scribe the data and the methods use to measure position
angles of jets and X-ray cavities, and Section 5 shows the
results. We discuss our findings in Section 6, while Sec-
tion 7 summarizes our work. Throughout this work we
assume a ΛCDM cosmology with H0=70 km s−1
Mpc−1
,
Ωm = 0.3, and ΩΛ = 0.7. Uncertainties are reported at
the 1σ confidence level. We define the radio spectrum as
Fν ∝ να
, where Fν is the flux density at frequency ν.
2. SAMPLE SELECTION
We select groups and clusters from the parent cata-
log presented in Hogan (2014); Hogan et al. (2015a,b),
where 59 central cluster and group galaxies have been
classified by their radio morphology on parsec scales.
The fairly uniform VLBA observations at 5 GHz are
suited to determine the presence and direction of jets in
the central dominant galaxies. Since we are driven by
3. 3
the aim of a Chandra – VLBA comparison, we include
only the sources that have more than 10ks of observa-
tions in the Chandra archive (45 out of 59 objects). By
excluding the objects that do not show evidence for ex-
tended radio jets in VLBA data and of X-ray cavities in
the Chandra data (see the analysis performed in Sect.
3 and 4), we obtain a final sample of 16 systems (see
Tab. 1). We note that all these systems host ionized
gas nebulae at their centers (as probed by optical line
emission, such as Hα; see Hogan 2014 and references
therein), strongly indicating the presence of a cooling
core in the host cluster or group.
The 59 radio-bright BCGs in the sample of Hogan et al.
(2015a,b) do not form a complete sample, but were
treated as representative of their parent, complete cat-
alog of over 700 clusters. Our further selection (as de-
tailed above and in Sect. 3) is mainly based on the pres-
ence of at least one jet in the radio images. Compact
radio sources may either be pointing directly towards us
(meaning that any jet would be projected on the core),
or may be in a fading phase (they were driving jets in
the past that are no longer visible). Thus, the sources
in our sub-sample constitute the BCGs with the most
active AGN at their centers, and with a small jet in-
clination angle to the plane of the sky. Far from being
complete, the clusters and groups in our sample (Tab.
1) are representative of systems where AGN feedback
activity is ongoing and vigorous. This matches our aim
to understand how frequently and why the pc-scale and
kpc-scale evidence of feedback are misaligned.
3. DATA AND METHODS
In the following, we describe the procedure used to
calibrate and analyze the VLBA and Chandra data, and
to obtain the final sample shown in Tab. 1.
3.1. VLBA radio data
Data reduction — The 5 GHz VLBA observa-
tions presented in Hogan (2014); Hogan et al.
(2015a,b) were performed in phase referencing mode
(project codes BE056A, BE056B, BE056C, BE063B,
BE063C, BE063E, BE063F, BE063H, BE063I, BE063J,
BE063K). The average time spent on each target source
was 20 minutes. The strategy we adopted to process the
data is based on standard reduction techniques in AIPS.
We first performed a correction of Earth orientation
parameters and ionospheric delays (tasks VLBAEOPS,
VLBATECR). Then, we solved for delays and amplitudes,
by applying digital sampling corrections (VLBACCOR),
removing instrumental delays on phases (VLBAMPCL),
calibrating the bandpass (BPASS), and applying the
corrections (VLBAAMP). To correct the time-dependent
Table 1. Our final sample of galaxy clusters and groups,
ordered by decreasing M500. The mass is taken from the
MCXC catalogue, which is based on the ROSAT X-ray lu-
minosity (Piffaretti et al. 2011). For 4C+55.16 (not present
in MCXC) the mass is taken from Zou et al. (2021).
Name redshift kpc/” M500
[1014
M⊙]
Abell 2390 0.230 3.67 8.95
ClG J1532+3021 0.362 5.04 8.16
4C+55.16 0.242 3.82 7.40
Abell 478 0.088 1.65 6.42
RX J1447.4+0827 0.376 5.16 4.60
Abell 1664 0.128 2.28 4.06
RXC J1558.3-1410 0.097 1.79 3.87
ZwCl 8276 0.076 1.44 3.24
Abell 496 0.033 0.65 2.91
ZwCl 235 0.083 1.56 2.80
Abell 2052 0.035 0.69 2.49
Abell 3581 0.022 0.44 1.08
NGC 6338 0.027 0.55 0.87
IC 1262 0.033 0.65 0.86
NGC 5098 0.036 0.72 0.52
NGC 5044 0.009 0.18 0.51
delays in phases, we fringe-fitted the data (FRING).
Sources with a flux density larger than 20 mJy – 30
mJy were self-fringed, while the others were referenced
to the phase calibrator. Ultimately, we applied the
calibration to the data and averaged the different IFs.
Between two and ten cycles of self-calibration were at-
tempted, and we found a significant improvement in
sensitivity only for sources with a flux density larger
than ∼50 mJy.
Morphological classification of the sources — Hogan (2014)
classified their radio sources as extended or unresolved
based on the morphology of the detected emission or as
undetected. We re-analyzed the calibrated data using
the software DIFMAP, which can be used to image, char-
acterize the morphology, and measure the flux density of
a source by fitting its calibrated visibilities with different
functions (an unresolved δ-function, a circular gaussian,
an elliptical gaussian, or a combination of these). Based
on our analysis, we classified as undetected the targets
for which no component with a flux density above 3 × σ
could be fit to the visibilities; as unresolved the tar-
gets described with a single component smaller than the
4. 4
beam area; and as extended the targets described by
least two components.
We verified the presence of extensions in all of the
sources classified as extended in the parent catalogue
of Hogan (2014). Out of the sources classified as un-
resolved in Hogan (2014), we found evidence for ex-
tended jet-like emission in NGC 5098, ZwCl 8276, and
RX J1447.4+0828. Specifically, Hogan (2014) reported
the possible presence of extended emission in NGC 5098
(based on a visual inspection), which we confirm to be
detected by fitting the visibilities in DIFMAP with an un-
resolved δ-function (the core) and a gaussian (the ex-
tended jet). The extended components we detected in
ZwCl 8276 and RXJ 1447+0828 are located along the
beam major axis and, on the basis of a by-eye inspec-
tion of the images, the sources would be classified as
unresolved; however, the best fit with DIFMAP is a com-
bination of a central bright component and two more
components on each side of the core in both clusters.
Of the sources classified as undetected in the parent
sample of Hogan (2014), our analysis revealed that
Abell 795 is in fact detected (but unresolved) at 20σ
(with σ = 50 µJy/beam), having a flux density of 1 mJy.
The location of the detected radio emission matches the
optical center of the BCG (RA, DEC = 9:24:05.3017,
+14:10:21.524), while the phase center of the observa-
tion is offset by ∼5′′
north-west, which may explain why
it was missed in the analysis of Hogan (2014).
Overall, the fitting procedure in DIFMAP allowed us to
confirm the presence of jets (at more than 5σ signifi-
cance) in 23 sources (out of the starting 45 BCGs, see
Sect. 2).
3.2. Chandra X-ray data
Data reduction — We retrieved the data from the Chan-
dra archive (cda.harvard.edu/chaser) and reprocessed
the observations using CIAO-4.14. Point sources were
identified using the tool wavdetect, and masked dur-
ing the analysis. For each target, we verified if the as-
trometry of the Chandra observation needed further cor-
rections beyond its nominal pointing accuracy (0.4′′
),
and proceeded to update the coordinates using the
wcs match and wcs update tools. We filtered the data
from periods contaminated by background flares. The
blank-sky event files have been selected as background
file, and normalized by the 9-12 keV count-rate of the
observation.
To investigate, in detail, the morphology of the ICM,
we produced images and corresponding background and
exposure maps in the 0.5 – 2 keV energy band. We
also used the software SHERPA to fit the images with
two-dimensional, elliptical double β models and produce
residual images, that can emphasize substructures in the
ICM/IGrM (see Fig. 3).
4. MEASUREMENT OF POSITION ANGLES
In the following, we describe the methods we employed
to measure the position angle of jets (on the parsec scale)
and of X-ray cavities (on the kpc scale). A schematic
representation is shown in Fig. 1.
Measuring the jet position angle in the plane of the sky —
The DIFMAP analysis returned the integrated flux (F)
and position relative to phase center in polar coordi-
nates (r, θ) of each component (see Appendix D). To
measure the position angle of the jet in the reference
frame centered on the core, we adopted the following
approach. We identified the core as the component with
the highest radio flux density in the image (see Fig. 2).
The position angle Φ⊥LOS in the plane of the sky of the
extended jet-like component at (r2, θ2) in the reference
frame centered on the core at (r1, θ1) is defined as:
Φ⊥LOS = arctan
r2 sin θ2 − r1 sin θ1
r2 cos θ2 − r1 cos θ1
, (1)
that is the angle between the line connecting (r2, θ2)
to (r1, θ1) and the horizontal (right ascension) axis. If
more than one jet is present (i.e. two sided sources),
we considered the average between the angles of the two
jets as the best estimate of the overall position angle.
We note that the statistical errors on the parameters ob-
tained from the DIFMAP fit may underestimate the real
uncertainties (see e.g., Deller et al. 2018). As a more ro-
bust estimate of the position angle uncertainty, δΦ⊥LOS,
we used the deconvolved angular width of the compo-
nent (circle or ellipse) describing the jet emission at its
distance from the core. In cases where the jet emission
was unresolved by the DIFMAP fitting procedure (i.e. the
component is a δ-function), we considered the angular
width of the beam at the distance of the jet from the
core. In practice, given a jet-like component described
by an ellipse with major semi-axis a and minor semi-
axis b, and located at a distance R from the core, the
uncertainty (in degrees) was determined as:
δΦ⊥LOS =
√
ab
R
!
×
180
π
, (2)
where a and b, in the case of an unresolved component,
are the beam major semi-axis and minor semi-axis, re-
spectively. We list in Tab. 2 our measurements of the
jet position angle perpendicular to the line of sight for
the systems in our sample. In Appendix A we show
the comparison with two alternative methods that pro-
vided consistent results with those presented here. Fur-
themore, we show in Appendix B that using archival
5. 5
Table 2. Position and inclination angles of the radio jets from the VLBA data and position angle of the X-ray cavities from the
Chandra data. (1) Cluster name. (2) Position angle in the plane perpendicular to the line of sight. (3) Jet/counter-jet ratio.
(4) Inclination angle in the plane parallel to the line of sight. (5) Name of the cavity (I stands for inner, O stands for outer).
(6) Cavity position angle. (7) Literature reference for the X-ray cavities. (8) Degree of misalignment between the jet direction
and the X-ray cavity direction (measured as the difference between columns 2 and 6).
Cluster Φ⊥LOS [◦
] R Φ∥LOS Cavity Θcav [◦
] Ref. ∆Ψ
Abell 2390 100.9 ± 28.5 2.1 20.3 ± 7.2 I1 5.2 ± 20.1 1, 2, 3 84.3
O1 152.4 ± 21.8 51.5
O2 -7.7 ± 22.4 71.4
ClG J1532+3021 353.2 ± 16.0 3.6 35.4 ± 11.3 I1 203.6 ± 26.9 4 30.4
I2 23.6 ± 26.9 30.4
4C+55.16 16.2 ± 67.2 16.4 57.5 ± 9.3 I1 268.1 ± 29.7 5 71.9
I2 36.7 ± 21.7 20.5
Abell 478 241.3 ± 25.4 5.8 49.5 ± 16.7 I1 99.0 ± 21.1 6, 7 37.7
I2 206.5 ± 28.6 34.8
RX J1447.4+0827 68.1 ± 15.5 1.1 3.6 ± 5.1 I1 80.4 ± 33.1 8 12.3
I2 265.6 ± 17.9 17.5
Abell 1664 280.9 ± 8.3 6.0 49.9 ± 16.3 I1 4.9 ± 24.5 9 84.0
I2 184.9 ± 24.5 84.0
O1 46.4 ± 30.6 54.5
O2 226.4 ± 30.6 54.5
RXC J1558.3-1410 153.4 ± 9.6 4.2 39.8 ± 12.8 I1∗
215.1 ± 19.7 This work 61.7
ZwCl 8276 265.8 ± 60.3 1.0 0.3 ± 5.0 I1 77.9 ± 30.2 10, This work 7.9
I2 257.9 ± 30.2 7.9
O1∗
114.9 ± 23.9 29.1
Abell 496 136.9 ± 15.6 1.1 2.4 ± 5.0 I1 126.6 ± 17.8 11, 12 10.3
I2 322.0 ± 33.1 5.1
O1 128.9 ± 20.5 8.0
ZwCl 235 153.4 ± 38.9 1.3 7.2 ± 5.3 I1 141.7 ± 17.3 13 11.7
I2 291.3 ± 13.1 42.1
Abell 2052 253.3 ± 17.5 1.1 3.6 ± 5.1 I1 84.3 ± 49.5 14 11.0
I2 271.6 ± 56.8 18.3
O1 37.1 ± 20.8 36.2
O2 248.2 ± 25.4 5.1
Abell 3581 189.7 ± 59.8 10.2 54.1 ± 12.4 I1 163.3 ± 27.4 15, 16 26.4
I2 325.9 ± 26.8 43.8
O1 338.8 ± 21.2 30.9
NGC 6338 293.7 ± 21.2 3.3 32.9 ± 10.9 I1 137.9 ± 44.2 17, 18 24.2
I2 317.9 ± 44.2 24.2
O1 210.0 ± 20.2 83.7
IC 1262 284.2 ± 15.6 7.0 51.2 ± 15.1 I1 85.3 ± 24.1 19 18.9
I2 265.3 ± 24.1 18.9
O1 286.9 ± 25.1 2.7
NGC 5098 244.7 ± 21.2 6.7 50.8 ± 15.4 I1 72.1 ± 32.5 20 7.4
I2 221.1 ± 30.3 23.6
NGC 5044 140.3 ± 19.4 1.2 4.4 ± 5.3 I1 68.7 ± 40.5 21, 22 71.6
I2 209.4 ± 35.9 69.1
O1 64.5 ± 16.1 75.8
O2 250.3 ± 21.9 70.0
Note—[1] Lima Neto Ulmer (2011); [2] Sonkamble et al. (2015); [3] Bı̂rzan et al. (2020); [4] Hlavacek-Larrondo et al. (2013b); [5]
Hlavacek-Larrondo et al. (2011); [6] Sun et al. (2003); [7] Giacintucci et al. (2014); [8] Prasow-Émond et al. (2020); [9] Calzadilla et al. (2019); [10]
Ettori et al. (2013); [11] Giacintucci (2016); [12] Dupke White (2002); [13] Ubertosi et al. (2023a); [14] Blanton et al. (2011); [15] Johnstone
et al. (2005); [16] Canning et al. (2013); [17] O’Sullivan et al. (2019); [18] Schellenberger et al. (2023); [19] Pandge et al. (2019); [20] Randall et al.
(2009); [21] O’Sullivan et al. (2014); [22] Schellenberger et al. (2021).
∗
: the X-ray cavity was identified in this work (see Appendix C for RXC J1558.3-1410 and Appendix E for the outer cavity in ZwCl 8276).
VLBA data at different frequencies returns position an-
gle measurements that are in good agreement with those
derived here from the 5 GHz radio maps.
Measuring the jet inclination angle along the line-of-sight —
As we are interested in the 3D geometry of the jets, we
used the jet/counter-jet flux ratio to constrain the incli-
nation angle of the jets with respect to the line of sight,
6. 6
Line of sight
Φ∥LOS
DEC axis
Plane of
the sky
RA axis
Φ⊥LOS
Jet
Line of sight
DEC axis
Plane of
the sky
RA axis
Θcav
Cavity
δΘcav
AGN
Core
Figure 1. Left: schematic representation of a core+jet system, showing the jet position angle Φ⊥LOS and the jet inclination
angle Φ∥LOS. Right: schematic representation of an AGN + cavity system, showing the bubble position angle in the plane of
the sky, Θcav, and the associated uncertainty, δΘcav.
which allows us to weight the importance of projection.
The jet/counter-jet flux ratio, Rj, is defined as:
Rj =
Fjet
Fc-jet
(3)
where Fjet and Fc-jet are the integrated fluxes of the
jet and of the counter-jet, respectively, measured in re-
gions placed over each feature. For one-sided objects,
the counter-jet flux was assumed to be lower than 5×σ.
The inclination angle of the jet in a plane parallel to
the line of sight, Φ∥LOS, can be computed using (e.g.,
Scheuer Readhead 1979):
cos Φ∥LOS =
1
β
×
R
1
2+α
j − 1
R
1
2+α
j + 1
, (4)
where α is the radio spectral index of the jets, assumed
to be α = −0.6. As the VLBA data probe the par-
sec scales, where the jets are still mildly relativistic, we
assumed a Lorentz factor 0.6 ≤ β ≤ 1 (see e.g., Giro-
letti et al. 2004; Giovannini et al. 2011). This returned
a possible range of inclination angles along the line of
sight. Thus, we used the median angle as our estimate
of Φ∥LOS, and the range width as the statistical uncer-
tainty. We also added in quadrature a systematic uncer-
tainty of 5◦
(that is Rj = 1.2, which could be intrinsic;
see e.g., McCarthy et al. 1991).
Measuring the X-ray cavities position angle — Out of
the 23 objects where we could detect one or two sided
jets from the VLBA data, there are literature indica-
tions for X-ray cavities in 15 objects. We inspected
the counts and residual images of the other 8 ob-
jects, searching for ∼ 20% − 30% decrements in sur-
face brightness at a signal-to-noise ratio greater than 3.
We found one object where a clear cavity was visible,
that is RXC J1558.3-1410 (see Appendix C). Hlavacek-
Larrondo et al. (2013a) noted the presence of cavities in
this cluster, but without detailing its/their position(s).
Thus, we are unable to confirm that the structure we
detect is coincident with the cavities they identified. We
also found evidence of an external cavity in ZwCl 8276,
besides the two inner bubbles noticed by Ettori et al.
(2013). The existence of this external cavity, (shown
in Fig. 3), is supported by the LOFAR detection of
lobe-like radio emission matching the position of this
outer bubble (Bı̂rzan et al. 2020).
Overall, there are 16 systems in which the Chandra data
allows us to measure the position angle of at least one
X-ray cavity. The following method was systematically
adopted to measure the position angle of the cavities
in the Chandra images of the 16 systems. For each
cluster or group, we measured the angle Θcav between
the center of the ellipse describing a cavity and the RA
axis with respect to the core of the central AGN, whose
precise location is known from the VLBA data. The
uncertainty in the position angle of the cavity, δΘcav, is
given by the width of the cavity in the direction perpen-
dicular to the line connecting the AGN and the center
7. 7
A
B
A
D
B
C
A
B
A
B
Abell 2390 ClG J1532+3021 4C+55.16 Abell 478
A
B
C
A
B
C
A
C
B
B A
C
Abell 496 ZwCl 235 Abell 2052 Abell 3581
A
B
C
A
B
A
B
A
B
NGC 6338 IC 1262 NGC 5098 NGC 5044
A
B
A
B
C
A
B
C
A
B
RX J1447.4+0827 Abell 1664 RXC J1558.3-1410 ZwCl 8276
Figure 2. VLBA images at 5 GHz of the systems in our sample. Labels indicate the position of the components identified
using DIFMAP (see Tab. 3). The contours overlaid in black start from 5 × σ (see the values in Tab. 3) and increase by a factor
of 2. The beam is overlaid with an orange ellipse in the bottom left corner. See Sect. 3.1 for details.
of the cavity (for a schematic representation see Fig. 1,
right panel).
We point out that we do not measure the inclination
angle of cavities to the line of sight, as done for the
radio jets. Relativistic arguments can constrain pro-
jection effects of radio jets on the pc-scale (see Eq. 4
and Scheuer Readhead 1979), whereas the depth of
cavities in a cluster or group atmosphere is non-trivial
to directly estimate from X-ray observations. Very few
works have attempted to constrain cavity inclination
angles, only in systems with remarkably deep cavities
(as in e.g., RBS 797, Cavagnolo et al. 2011) and with
several assumptions. Besides, the detectability of X-ray
cavities is hampered when the structures lie at large
angles (greater than 45◦
) from the plane of the sky (see
Enßlin Heinz 2002; Mroczkowski et al. 2022), so that
the majority of detected X-ray cavities in groups and
clusters lie at less than 45◦
from the plane of the sky
8. 8
Abell 2390 ClG J1532+3021 4C+55.16 Abell 478
RX J1447.4+0827 Abell 1664 RXC J1558.3-1410 ZwCl 8276
Abell 496 ZwCl 235 Abell 2052 Abell 3581
NGC 6338 IC 1262 NGC 5098 NGC 5044
I1
O1
O2
I1
I2
I1
I2
I1
I2
I2
I1
I2
I1
O1
O2
I1
I1
I2
O1
I2
I1
O1
I1
I2
I2
I1
O1
O2
O1
I1
I2
I2
I1
O1
I1
I2
O1
I1
I2
I1
I2
O2
O1
50’’ 20’’ 15’’ 25’’
10’’ 15’’ 30’’ 20’’
40’’ 15’’ 30’’ 45’’
50’’ 80’’ 10’’ 30’’
Figure 3. Residual Chandra images of the systems in our sample. Overlaid in green are the X-ray cavities (see Tab. 2 for
details and literature references), while the white line shows the orientation of the radio jet in the plane of the sky, Φ⊥LOS. The
red cross shows the position of the central AGN. See Sect. 6.2 for details.
(Brüggen et al. 2009). Thus, we assume that the X-ray
cavities in our sample are not far from the plane of the
sky. While this represents a limitation of this work, we
are confident that any tentative cavity inclination angle
would likely be smaller than the associated uncertainty.
Out of the 45/59 objects of Hogan et al. (2015b,a)
with more than 10 ks of Chandra data, the above pro-
cedures led us to consider only the 23/45 with one- or
two-sided jets, and then the 16/23 with at least one
X-ray cavity. Our final sample, thus comprising 16 ob-
jects, is listed in Tab. 1. The sample covers a mass
range of 5 × 1013
M⊙ ≤ M500 ≤ 9 × 1014
M⊙, and is
composed of 11 galaxy clusters and 5 galaxy groups.
For each object we were able to measure the position
and inclination angles of the jets (Φ⊥LOS, Φ∥LOS) and
the position angle of the cavities (Θcav). These values
are reported in Tab. 2.
5. RESULTS
5.1. Jet – cavity misalignments in the plane of the sky
Focusing on the position angles in the plane of the
sky of jets and X-ray cavities, we defined the quantity
∆Ψ = |Φ⊥LOS − Θcav|, which represents the degree of
misalignment between the jet direction (measured on
parsec scales) and the X-ray cavity direction (measured
on kiloparsec scales). The values that ∆Ψ can assume
range between 0◦
– 90◦
, with ∆Ψ = 0◦
indicating a per-
9. 9
ntot = 43
nΔΨ 45 = 14
fΔΨ 45 = 0.33
Every jet-cavity pair per system
ntot = 16
nΔΨ 45 = 6
fΔΨ 45 = 0.38
Most misaligned jet-cavity pair per system
ntot = 16
nΔΨ 45 = 5
fΔΨ 45 = 0.31
Innermost jet-cavity pair per system
Figure 4. Left: Plot of jet position angle in the plane of the sky versus cavity position angle for the 16 systems in our sample.
Each point is a jet – cavity pair, meaning that systems with more than one X-ray cavity are represented by more than one point
on the plot. The gray shaded areas represent spaces of the plot where the difference ∆Ψ = Φ⊥LOS − Θcav is greater than 45◦
.
Jet – cavity pairs falling inside these areas are represented with circles, while those falling outside these areas are represented
with squares. The points are color-coded according to the cluster or group they belong to (see the top legend). Labels on the
right of each point indicate the corresponding cavity (see Tab. 2). Top right: histogram of ∆Ψ for the 43 jet – cavity pairs
of the systems in our sample. Center right: histogram of the jet – cavity pairs with the largest ∆Ψ for each systems. Bottom
right: histogram of the jet – innermost cavity pair for each system. In each panel, the red dashed line shows the threshold of
45◦
between aligned and misaligned jet – cavity pairs.
fect alignment and ∆Ψ = 90◦
indicating an orthogonal
misalignment. For the sake of clarity, we note that for
a cluster or a group with a number N of X-ray cavities,
there are N pairs of (Φ⊥LOS, Θcav) for which an esti-
mate of ∆Ψ can be obtained.
From now on, we arbitrarily classify as aligned the jet
– cavity pairs for which ∆Ψ 45◦
, and as misaligned
the jet – cavity pairs for which ∆Ψ 45◦
. In the last
10. 10
column of Tab. 2 we list the values of ∆Ψ for the cavi-
ties of each cluster or group in our sample. Additionally,
we show in Fig. 4 a plot of Θcav versus Φ⊥LOS for the
jet – cavity pairs in our sample. Given that the 180◦
ambiguity in the definition of the position angle does
not allow one to immediately evaluate ∆Ψ from this fig-
ure, we overplot as gray shaded areas the regions where
∆Ψ 45◦
.
Among the 16 systems in our sample, there are 10
systems in which all the detected X-ray cavities are
aligned with the radio jet seen at 5 GHz; these
are ClG J1532+3021, Abell 478, RX J1447.4+0827,
ZwCl 8276, Abell 496, ZwCl 235, Abell 2052, Abell 3581,
IC 1262 and NGC 5098. An additional 2/16 objects,
4C+55.16 and NGC 6338, have at least one X-ray cav-
ity that is aligned with the radio jet. In the remaining
4/16 objects, Abell 2390, Abell 1664, RXC J1558.3-1410
and NGC 5044, all the detected X-ray cavities are found
at more than 45◦
from the axis of the radio jet. We pro-
vide a short summary of the properties of each system
in Appendix E.
To further investigate the fraction of misaligned
systems/X-ray cavities, we show in Fig. 4 (top right)
the histogram of ∆Ψ for the 43 jet – cavity pairs of our
sample. As expected from models of cavity formation,
the majority of the X-ray cavities are aligned with the
radio jet. However, as noted in the introduction, cases of
spatial misalignment are known. Indeed, taking 45◦
as
a threshold for a misaligned cavity-pair, there are 14/43
misaligned jet – cavity pairs, that corresponds to a frac-
tion of 33%. A similar argument can be made by con-
sidering, for each cluster or group, only the jet – cavity
pair with the largest ∆Ψ. The corresponding histogram
in Fig. 4 (center right) shows that in 6/16 systems there
is a cavity – jet pair with ∆Ψ 45◦
, corresponding to a
fraction of 38%. Moreover, restricting the histogram to
the jet – innermost cavity pair for each system (Fig. 4,
bottom right), we find a fraction of 5/16 = 31% of sys-
tems with ∆Ψ 45◦
. These results suggest that there
is a 30%-40% chance to find a misalignment larger than
∆Ψ = 45◦
when observing a cluster/group with a de-
tected jet and at least one X-ray cavity.
We note that in the histograms of Fig. 4 there is a peak
at ∆Ψ ≈ 70◦
− 80◦
, which comprises the cases where
the jet and the cavity are nearly orthogonal. We discuss
this feature and its interpretation in Sect. 6.3.
5.2. Jet inclination angle with respect to the line of
sight
As reported in Sect. 4, we constrained the jet incli-
nation in a plane parallel to the line of sight using the
jet – counterjet flux density ratio (see Tab. 2). The
angle Φ∥LOS ranges between 0◦
(jets lying in the plane
of the sky) to ∼ 60◦
. There are 6/16 systems with 0◦
≤
Φ∥LOS ≤ 10◦
(RX J1447.4+0827, ZwCl 8276, Abell 496,
ZwCl 235, Abell 2052, and NGC 5044), 4/16 systems
with 10◦
≤ Φ∥LOS ≤ 45◦
(Abell 2390, ClG J1532+3021,
RXC J1558.3-1410, and NGC 6338), and 6/16 systems
with Φ∥LOS ≥ 45◦
(4C+55.16, Abell 478, Abell 1664,
Abell 3581, IC 1262, and NGC 5098).
We notice that the lack of systems with jets nearly
aligned along the line of sight is set by the combination
(1) of our criterion of having at least one jet in the ra-
dio images (we are avoiding objects with Φ∥LOS ≈ 90◦
);
(2) of the assumptions on β and α in Eq. 4 (that is,
we do not consider superluminal motion, β 1, or jets
with an inverted spectrum, α ≥ 0); (3) of the limited
dynamic range of the VLBA snapshot data (∼20 min
of time on source), thay may hide faint counterjets in
one-sided sources; (4) of spherical geometry arguments:
a given polar angle interval ∆Φ covers more area on the
sphere near the equator than near the poles, thus we ex-
pect only a small fraction of randomly pointed vectors
to be pointed at us.
6. DISCUSSION
In the following, we test different scenarios to explain
the alignments and misalignments between jets and X-
ray cavities in our sample. After assessing the relative
importance of external factors, that is projection effects
and environmental disturbances, we turn to the discus-
sion of effects related to the central engine. Specifically,
we show how the distribution of ∆Ψ for the clusters and
groups in our sample can provide insights on the likeli-
hood of jet reorientation, and we consider the timescales
of such mechanisms.
6.1. Projection effects
As noted in Sect. 5.1, there are systems in our sample
where some X-ray cavities are misaligned by more than
45◦
from the radio jet of the AGN. However, there is
the possibility that the misalignment is only apparent.
Indeed, projection effects may cause a large apparent
offset, even though the actual 3D misalignment between
jets and cavity directions is small. Using the informa-
tion obtained from the analysis of the jet direction with
respect to the line of sight (Sect. 4 and 5.2) we can sys-
tematically reconstruct the 3D geometry of jets and ver-
ify whether projection effects may reconcile the largest
misalignments we found.
We show in Fig. 5 (left panel) the jet inclination along
the line of sight, Φ∥LOS, plotted against the difference
between the jet and the cavity position angles in the
plane of the sky, ∆Ψ. This figure can be used as a di-
agnostic plot for the degree of misalignment of each jet
11. 11
ntot = 43
nΔΨ 45 = 14
fΔΨ 45 = 0.33
ntot = 27
nΔΨ 45 = 9
fΔΨ 45 = 0.3
Every jet-
cavity pair
per system
Only those
mainly in the
plane of the sky
Figure 5. Left: Diagnostic plot of misaligned jets and X-ray cavities. The jet inclination angle along the line of sight, Φ∥LOS, is
plotted against the difference between the jet and the cavities position angles in the plane of the sky, ∆Ψ. Points are color-coded
according to the cluster or group they belong to (see the top legend). Labels on the right of each point indicate the corresponding
cavity (see Tab. 2). Top right: same as in Fig. 4 (top right panel), but with the addition of the orange line, that is the fit
with a Gaussian function to the systems with ∆Ψ ≤ 45◦
(see Sect. 6.3 for details). Bottom right: same as the top panel but
including only the systems for which projection effects are negligible, that is Φ∥LOS 45◦
. In both panels, the red dashed line
shows the threshold of 45◦
used to classify jet – cavity pairs as aligned or misaligned.
– cavity pair in the systems of our sample. As done be-
fore, we use Φ∥LOS = 45◦
and ∆Ψ = 45◦
as thresholds
between jets in the plane of the sky or along the line
of sight and between aligned or misaligned jet – cav-
ity pairs, respectively. We can thus divide the 43 jet
– cavity pairs between the four quadrants of the plot,
obtaining the following results:
• Bottom-left quadrant: aligned jet – cavity pairs which
are mainly lying in the plane of the sky.
• Upper-left quadrant: aligned jet – cavity pairs where
the jet is primarily oriented towards us.
• Upper-right quadrant: misaligned jet – cavity pairs
where the jet is primarily oriented towards us.
• Bottom-right quadrant: misaligned jet – cavity where
the jet is mainly lying in the plane of the sky.
Overall, the (mis)alignments of jet – cavity pairs that are
located in the two bottom quadrants, where projection
effects are relatively negligible, are robustly confirmed
even in 3D. By restricting the analysis to these jet – cav-
ity pairs (a total of 27 pairs), we still find that a fraction
of 9/27 = 30% is misaligned by more than 45◦
, up to
nearly orthogonal misalignments. Such fraction of mis-
aligned jets in the plane of the sky is clearly independent
of the inclination angle along the line of sight. There-
fore, projection effects may account for an apparently
large ∆Ψ only in a fraction (∼35%) of the misaligned
jet – cavity pairs in our sample (as in Abell 1664 or for
the cavity I1 in 4C+55.16).
6.2. The environment
In this subsection we consider whether environmen-
tal effects may favor misalignments between successive
AGN outbursts. First, we note that over the mass range
covered by our sample (5 × 1013
M⊙ ≤ M500 ≤ 9 × 1014
M⊙) there is no clear evidence for the degree of mis-
alignment of the different jet – cavity pairs being re-
lated to the mass of the host halo. Based on the 16
systems in our sample, dramatic changes in jet direction
can be found both in massive galaxy clusters (such as
Abell 2390, with ∆Ψmax = 84.3◦
) and in galaxy groups
12. 12
(such as NGC 6338, with ∆Ψmax = 83.7◦
, or NGC 5044,
with ∆Ψmax = 75.8◦
).
A potentially important question is whether gravita-
tional perturbances that trigger large scale gas motions
could play a major role. Specifically, cavities pointing to
a different direction than the jets may have been shifted
from their original axis by the gas motions.
If gas bulk motions (such as sloshing) were responsi-
ble for the jet – cavity misalignments, we should expect
misaligned pairs to be more likely found in disturbed
clusters and groups. Typical evidence of sloshing in-
clude a spiral morphology of the ICM/IGrM, and/or
the presence of one or more cold fronts. We checked in
the literature if the objects in our sample are reported
to be in a sloshing state. Interestingly, all the systems
are dynamically disturbed, with all but one (NGC 6338,
which is merging with another group) showing evidence
of sloshing. The relevant references are given in Tab. 2.
Even though no dedicated X-ray studies are available for
RXC J1558.3-1410, we remark that the Chandra image
reveals a bright spiral residual feature in the ICM (see
Fig. 9 in Appendix C), which indicates that sloshing is
likely present also in this system.
Nice comparisons are offered by Abell 496, Abell 3581,
Abell 1664 and NGC 6338 (see Fig. 3), which are all
strongly disturbed systems. In Abell 496 and Abell 3581
the different generations of X-ray cavities are nearly
aligned with each other and with the radio jet. Con-
versely, in Abell 1664 and NGC 6338 the different gen-
erations of X-ray cavities are largely misaligned by more
than 45◦
from each other and from the radio jet. Even
though we cannot exclude that in some systems the
present position of the X-ray cavities may have been
influenced by the large scale motions, we argue that the
environment does not play the major role, as gas dy-
namical perturbations are present in the whole sample.
Sloshing may become a dominant mechanism for the dy-
namics of X-ray cavities at later times (as for the oldest,
detached radio lobe of NGC 5044, see O’Sullivan et al.
2014), since sloshing timescales (around 108
− 109
yr,
e.g., Su et al. 2017) are usually an order of magnitude
larger than the age of X-ray cavities (around 106
−107
yr,
e.g., Bı̂rzan et al. 2004; see also Sect. 6.4).
6.3. The likelihood of jet reorientation
The above results argue against projections or envi-
ronmental effects, alone, being able to explain the jet
– cavity misalignments. All in all, it seems more likely
that the large changes in direction are related to actual
reorientation of the SMBH-driven jets. We now turn to
the questions of how likely it is for jets to experience
reorientation, and whether there is a favored angle.
Our analysis of Sect. 5.1 unveiled that ∼ 30% − 40% of
the jet – cavity pairs in our sample have a ∆Ψ larger
than 45◦
. Furthermore, when excluding systems that
may be biased by projection effects (see Sect. 6.1), we
find that 30% of jet – cavity pairs are misaligned by an
angle (in the plane of the sky) ranging between 45◦
and
90◦
. This suggests that a change in the jet position an-
gle of AGN may be a relatively common mechanism, as
roughly 1/3 of the X-ray cavities in our sample are more
than 45◦
away from the currently driven jets.
A peculiar feature in the distribution of ∆Ψ is the peak
around ≈ 75◦
. We note that the peak is resilient to
the systems aligned along the line of sight being re-
moved from the histogram (see Fig. 5, bottom right
panel). If no changes in time of the position angle of
the jets occurred, one might expect that cavities and
corresponding jets should always be perfectly aligned,
i.e. ∆Ψ = 0◦
. This is clearly an idealized case, as
there are several effects that contribute to widening the
distribution around zero. These can be both intrinsic
to the physics of jets and X-ray cavities (such as slow
precession of the jet axis over time, cavities expanding
asymmetrically, or buoyant forces governing the motion
of bubbles at later times1
) and related to observational
biases (cavities not being perfect ellipses, resolution of
radio and X-ray observations, projection effects). All of
these likely result in a broadening of the distribution to
a nearly Gaussian shape. This is indeed the case for the
jet – cavity pairs with ∆Ψ ≤ 45◦
: fitting a Gaussian
function to this side of the distribution we find a mean
µ = 0.0◦
±1.2◦
with standard deviation σ = 27.6◦
±1.6◦
(see Fig. 5, top right panel). This scatter of ∼ 30◦
ex-
presses the above widening effects.
The effect of jet reorientation on the histogram de-
pends on whether there is a favored angle by which
jets are reoriented. If jet reorientation caused a ran-
dom change in the position angle of the jets, one would
expect a uniform distribution of misaligned jets and
X-ray cavities combined with the Gaussian-like distri-
bution at ∆Ψ 45◦
. However, the presence of the
peak at ∆Ψ ∼ 75◦
in Fig. 5 (right panels) may sug-
gest that when a change in jet orientation between suc-
cessive AGN outbursts occurs, the change in position
angle is more likely to be large, rather than randomly
1 In case of a non-spherical potential well, a buoyant bubble will
preferentially rise in the direction of the shallower potential (that
is the minor axis of the dominant galaxy, in case of an elliptical
morphology). However, the majority of radio galaxies already
have their jets oriented within ∼ 30◦ of the optical minor axis of
their host (Palimaka et al. 1979; Battye Browne 2009; Vazquez
Najar Andernach 2019), which limits the magnitude of mis-
alignments induced by an asymmetric potential.
13. 13
distributed between 0◦
− 90◦
. That is, we may cau-
tiously propose that the mechanism of jet re-orientation
favors large changes in jet position angle, causing nearly
orthogonal misalignments between the successive AGN
outbursts.
We note that these conclusions would strongly benefit
from increasing the sample size to include a larger num-
ber of objects. We can estimate the robustness of the
above result for our sample of 16 clusters with a total
of 43 X-ray cavities. We performed 103
realizations of
drawing 43 values between 0◦
−90◦
from the combination
of a Gaussian (with µ, σ set to those derived above) and
a uniform distribution. The relative number of points
drawn from the Gaussian was set to 29/43 (the jet –
cavity pairs with ∆Ψ ≤ 45◦
), while the remaining 14/43
values (the jet – cavity pairs with ∆Ψ ≥ 45◦
) were drawn
from the uniform component. We find that the proba-
bility of having n70◦−90◦ /n45◦−70◦ 2 (as observed) is
of 1.6%, thus we can reject the uniform distribution at
∼ 2.5σ confidence.
We also note that this is not the first time that a sec-
ondary peak at large angles is found when studying small
and large scales misalignments. Earlier works found a
secondary peak at around 90◦
(Pearson Readhead
1988; Wehrle et al. 1996; Cao 2000), more recently con-
firmed in Kharb et al. (2010). These works were based
on radio data (misalignments were evaluated through
VLA and VLBA comparisons), and the sources of those
samples were mainly blazars or quasars, for which pro-
jection effects are certainly not negligible. In our study
we find a very similar result (a peak at ∆Ψ ∼ 70◦
−80◦
)
using the X-ray counterparts of large scale radio lobes
(the cavities), and, most importantly, even when re-
stricting the analysis to sources where projection effects
are negligible (see Fig. 5, bottom right panel). There-
fore, while limited by the statistics of our sample, we
confirm the earlier claims of a bimodality in the distri-
bution of misalignments. In turn, this supports the idea
that the mechanism behind the changes in jet orienta-
tion favors large misalignments over small ones.
6.4. The timescales and mechanism of jet reorientation
The observed misalignments raise the question of how
quickly jets can change propagation direction over time.
To investigate this point, we searched in the literature
references listed in Tab. 2 which X-ray cavities in our
sample had an estimate of their ages (24 out of 43 X-ray
cavities). We show in Fig. 6 (left panel) a plot of ∆Ψ
versus the age of each X-ray cavity (obtained through
different methods, which typically agree within a factor
of two; see Bı̂rzan et al. 2004). No clear trend is visible
in this figure. This may indicate that larger changes
in jet axis orientation do not always occur on longer
timescales. By focusing on the systems with ∆Ψ 45◦
,
we see that the young X-ray cavities in NGC 5044 and
in Abell 1664, likely formed only a few Myrs ago, are
already misaligned by a large angle from the radio jet
currently being driven by the central engine. The case
of NGC 5044 is remarkable, with the 1 Myr old inner X-
ray cavities being at ∼ 70◦
from the jet seen in VLBA
images. Schellenberger et al. (2021) discussed many
possibilities for such misalignment, ruling out binary
black holes and precession scenarios.
In the case that the jet’s direction of propagation is
linked to the spin of the rotating SMBH only, dra-
matically altering the SMBH rotation axis on short
timescales is non-trivial. To address this issue, the
case has been made that the jet direction could be
influenced by the accreting material. We point out
that, in the following discussion, we do not assume a
one-to-one relation between an accretion episode and
a jet episode. Rather, during continuous gas accre-
tion, the variations of the accretion rate, the magnetic
field, or the spin of the SMBH may drive the for-
mation of a relativistic jet (e.g., Blandford Znajek
1977; Meier 2001; Wu Cao 2008; Čemeljić et al. 2022).
Babul et al. (2013) argued that infalling clouds may
form a thin accretion disk misaligned from the spin axis
of the SMBH. In this case, the orientation of the disk
would influence the direction of the emerging jet. Thin
accretion disks are usually associated with radiatively
efficient AGN with high accretion rates, such as quasars
and Seyferts. By contrast, radiatively inefficient radio
galaxies, which are common at the center of galaxy
groups and clusters, are more likely powered by geomet-
rically thick accretion flows with a low accretion rate
(Ghisellini Celotti 2001). We also note that our anal-
ysis in Sect. 6.3 suggests that the change in jet position
angle over time is more likely to be nearly orthogonal,
rather than completely random between 0◦
− 90◦
. This
is reminiscent of X-shaped radio galaxies, where the
Bardeen – Petterson mechanism (Bardeen Petter-
son 1975) may cause orthogonal reorientation of the
jets (Liu 2004). However, X-shaped radio galaxies are
preferentially high accretion rate AGN (e.g., Machalski
et al. 2016; Garofalo et al. 2020; Giri et al. 2022).
The question thus arises whether the systems with
reoriented jets can have larger accretion rates, thus
temporarily allowing the disk to influence the spin of
the SMBH. To investigate this point, we derived the
Eddington ratio of the systems in our sample. The
14. 14
0 5 10 15 20 25 30 35 40
tcav [Myr]
0
10
20
30
40
50
60
70
80
90
[°]
I1 I2
I1
I2
I1
I2
I1
I2
I1
I2
I1
I2
I1
I2
O1
I1 I2
O1
I1
I2
I1
I2
I1
I2
O1
O2
ClGJ1532+3021
4C+55.16
Abell478
RXJ1447.4+0827
Abell1664
ZwCl235
Abell3581
NGC6338
IC1262
NGC5098
NGC5044
10 7 10 6 10 5 10 4 10 3
Eddington ratio Lbol/LEdd
0
20
40
60
80
100
[°]
Abell2390
4C+55.16
Abell478
Abell1664
RXCJ1558.3-1410
ZwCl8276
Abell496
ZwCl235
Abell2052
Abell3581
IC1262
NGC6338
NGC5098
NGC5044
Figure 6. Left panel: Jet – cavity position angle difference ∆Ψ versus cavity age tcav for the cavities in the systems of Tab.
2 with an available estimate of the age from the literature. Right panel: Largest jet – cavity position angle difference ∆Ψ for
each system in our sample versus the Eddington ratio of the central AGN (see Sect. 6.4 for details). In the right panel, only
the 14/16 systems with available measurements of Lbol and LEdd are plotted.
Eddington ratio is defined as:
fEdd =
Lbol
LEdd
, (5)
where Lbol is the AGN bolometric luminosity, and LEdd
is the Eddington luminosity. The latter is defined as:
LEdd = 1.3 × 1038
M[M⊙] erg/s, (6)
where M is the mass of the SMBH (see Czerny You
2016 for a review). The Lbol and LEdd for the majority
of the systems in our sample were retrieved from Mezcua
et al. (2018), who used the 2 – 10 keV X-ray nuclear lu-
minosity and a bolometric correction factor of 20 to es-
timate Lbol. For NGC 6338, NGC 5044, and 4C+55.16
the bolometric and Eddington luminosities were derived
from the X-ray nuclear luminosity and black hole mass
reported in Russell et al. (2013), respectively, adopting
the same bolometric conversion factor of Mezcua et al.
(2018). A similar method has been used to derive Lbol,
LEdd from the literature references of NGC 5098 (Ran-
dall et al. 2009; Arzoumanian et al. 2021) and IC 1262
(Bi et al. 2020; Arzoumanian et al. 2021). No useful data
is available for ClG J1532+3021 and RX J1447.4+0827.
Fig. 6 (right panel) shows the largest degree of mis-
alignment of each cluster or group in our sample ver-
sus the Eddington ratio. We find low levels of accre-
tion, fEdd ≤ 10−3
, for all the AGN, with an aver-
age of fEdd = 1.5 × 10−5
. For comparison, the iso-
lated X-shaped radio galaxies in Joshi et al. (2019) have
fEdd = 4 × 10−3
. Additionally, the systems in our sam-
ple with and without reoriented jets have similar accre-
tion efficiencies.
Likely, the Eddington ratios we measure represent the
current accretion efficiencies. Since the accretion rate
can flicker over time (e.g., Schawinski et al. 2015; King
Nixon 2015), we may hypothesize that the AGN with
reoriented jets have been highly accreting in the past,
thus allowing the Bardeen-Petterson effect to trigger
the reorientation of the jets. While we cannot verify
this hypothesis, the above result suggests that any high-
accretion efficiency phase must have been short enough
to allow the AGN to quickly transition back to a low-
accretion efficiency phase (the one observed at present).
In this context, theoretical and computational works
have argued that the radiatively inefficient, geometri-
cally thick disk (ADAF-like, Narayan Yi 1995) in the
core of cluster and group-central galaxies may be fed by
individually infalling molecular clouds, whose angular
momentum varies over time (e.g., Gaspari et al. 2017;
Soker 2022). These parcels of cold gas may temporarily
boost the accretion rate (e.g., Gaspari et al. 2015).
For completeness, Lalakos et al. (2022) showed how
during the first phases of AGN activity the jets can
naturally experience intermittency and fast (down to
10−2
Myr) changes in orientation, even at low accre-
tion efficiencies. However, the timescales shown in Fig.
6 (left panel) do not reflect a rapid flickering of jet di-
rection in the first ∼ 1 Myr of AGN activity, before
stabilizing to a collimated and stable structure. Indeed,
in NGC 5044 there are at least two aligned outbursts
(with an age of ∼13 Myr) that preceded the youngest,
misaligned one (the one seen on VLBA scales), which
indicates that flickering would have had to last at least
an order of magnitude longer than the timescales ex-
plored in Lalakos et al. (2022). The same holds e.g., for
NGC 6338, and likely for Abell 2390 (note that although
there are no estimates of the X-ray cavity ages in this
system, the 100 kpc – scale bubbles O1 and O2 are plau-
15. 15
sibly older by 10 − 100 Myr than the current radio jet -
see also Alcorn et al. 2023).
Therefore, if jet reorientation in cluster and group-
central galaxies is driven by a temporary phase of high
accretion efficiency, this phase must be short lived.
Babul et al. (2013) and Garofalo et al. (2020) estimated
that the quasar-like phase should last a few Myrs to al-
low any appreciable changes in the jets direction. This
is a reasonable timescale for most of the AGN in our
sample, for which the cavity ages shown in Fig. 6 (left
panel) are larger than ∼ 5 − 10 Myr.
However, NGC 5044 is an exception. The difference
in time between the two most recent outbursts in
NGC 5044 is of ≤1 Myr, meaning that the thin disk
phase in this system should have lasted only a few
104
− 105
yr (see also Schellenberger et al. 2021). Thus,
it is possible that other scenarios apply to this peculiar
system. For example, McKinney et al. (2013) showed
that while the innermost region of a thick accretion flow
remains aligned with the BH spin axis over time, the
outer accretion flow can be tilted by a large angle. This
outer thick disk can gradually push away and deflect the
jet, which can eventually bend by up to 90◦
and con-
tinue to propagate orthogonal to the SBMH spin axis.
Such deflection occurs at 100 gravitational radii (rg),
and by 300 rg the orthogonal deflection is completed.
For NGC 5044 (M = 2 × 108
M⊙ and 1′′
= 150 pc, see
Schellenberger et al. 2021), resolving such scales with
radio observations would require a resolution of ≤ 0.5
mas. If any outer thick disk is deflecting the jets in
NGC 5044, this can only be confirmed with radio obser-
vations that have a resolution of an order of magnitude
higher than those currently available.
Overall, we are unable to pinpoint the mechanism that
can exhaustively explain the observed properties of the
jet reorientation mechanism: the re-alignment of the jets
can be fast (down to ≤ 1 Myr) and nearly orthogonal
changes in position angle seem favored. If any tempo-
rary highly-efficient accretion phase has driven jet reori-
entation in the past, it must have been rather short lived
(≤ a few Myr). The solution may be provided in the fu-
ture by models, simulations and observations that can
account for the properties of AGN outbursts on scales
that span several orders of magnitude (between 10−4
pc
to 104
pc).
7. CONCLUSIONS
In this work we presented the analysis of VLBA and
Chandra data of 16 cool core galaxy clusters and galaxy
groups, to understand how common jet and cavities mis-
alignments are and which causes may be responsible for
such mismatch. Below we report our main findings.
• For each system we measured the jet position an-
gle (Φ⊥LOS) and the cavity position angle (Θcav) in
the plane of the sky. Using the full sample and se-
lected subsets, we found that between 30% to 38%
of the jet – cavity pairs are misaligned by more than
∆Ψ = Φ⊥LOS − Θcav = 45◦
.
• By measuring the jet inclination angle along the line
of sight (Φ∥LOS) we determined that projection effects
may bias our measurement of ∆Ψ in around half of the
sample. Restricting the analysis to the AGN whose
jets lie in the plane of the sky, we still found a fraction
of ∼ 30% of misaligned systems, supporting the above
conclusions.
• We retrieved information on the dynamical state of the
host clusters and groups, finding that all are examples
of disturbed systems. Even though we cannot exclude
that gas motions may have perturbed X-ray cavities
away from their original trajectory in some systems,
the ubiquity of disturbances excludes the possibility
that a perturbed environment plays the major role in
producing large misalignments.
• The distribution of ∆Ψ appears to be the combination
of a Gaussian centered at 0◦
with σ = 27.6◦
± 1.6◦
plus a peak around ∆Ψ ∼ 75◦
. We conclude that, at
2.5σ significance, large misalignments are favored over
small ones.
• By considering the age of the X-ray cavities, we find
that larger misalignments (∆Ψ 75◦
) do not occur
on longer timescales, with the shortest time difference
being around 1 Myr in NGC 5044. Considering our
findings and reviewing previous literature results, we
cautiously propose that in addition to the spin axis
of the SMBH, the geometry of the accretion flow may
influence the direction of jet propagation.
8. ACKNOWLEDGMENTS
We thank the referee for their useful comments on our
work. FU thanks the Smithsonian Astrophysical Obser-
vatory for the hospitality and support during his visit.
FU acknowledges support provided by the Marco Polo
program. The authors acknowledge support for this
work provided by the National Aeronautics and Space
Administration (NASA) through Chandra Award Num-
ber GO1-22125X issued by the Chandra X-ray Center,
which is operated by the Smithsonian Astrophysical Ob-
servatory for and on behalf of the National Aeronautics
Space Administration under contract NAS8-03060. Ba-
sic research at the Naval Research Laboratory (NRL)
is supported by 6.1 Base funding. WF acknowledges
support from the Smithsonian Institution, the Chandra
High Resolution Camera Project through NASA con-
tract NAS8-03060, and NASA Grants 80NSSC19K0116,
16. 16
GO1-22132X, and GO9-20109X. The National Radio
Astronomy Observatory is a facility of the National Sci-
ence Foundation operated under cooperative agreement
by Associated Universities, Inc. This work made use of
the Swinburne University of Technology software cor-
relator, developed as part of the Australian Major Na-
tional Research Facilities Programme and operated un-
der licence. This research has made use of data obtained
from the Chandra Data Archive and the Chandra Source
Catalog, and software provided by the Chandra X-ray
Center (CXC) in the application packages CIAO and
Sherpa.
Facilities: NRAO,CXO
Software: astropy (Astropy Collaboration et al.
2013, 2018), APLpy (Robitaille Bressert 2012), Numpy
(Harris et al. 2020), CIAO (Fruscione et al. 2006), AIPS
(Greisen 2003), DIFMAP (Shepherd et al. 1994), SHERPA
(Burke et al. 2021).
APPENDIX
A. ALTERNATIVE METHODS TO MEASURE JETS POSITION ANGLES ON VLBA SCALES
In this Appendix we show the two other methods we adopted to measure the position angle of the jets in a plane
perpendicular to the line of sight.
• Largest linear size: we filtered the VLBA images to exclude all the pixels with a flux density lower than 5σ.
Then, we computed the distance of each pixel from all the others. The two most distant pixels set the largest
linear size of the radio source. The jet position angle is thus measured as the slope of the line that connects the
two most distant pixels. The uncertainty on the position angle is the relative angular width of the beam with
respect to the linear size, meaning that larger sources have smaller relative uncertainties. A potential weakness
of this method is that in radio images the pixels are usually not independent, as the real resolution element is the
beam, not the individual pixel. Local substructures (smaller than than the beam) may generate large differences
in position angle for small differences in distance between adjacent pixels.
• Fitting the radio image: assuming that in the simplest configuration a core+jet morphology can be described as
a straight line connecting two points (the core and the jet), we fitted the coordinates of the pixels (above 5σ) in
the VLBA images with a straight line, thus treating the image as a scatter plot. Following this analogy, the jet
position angle is the slope of the best-fit linear regression. During fitting, the pixels were weighted by their flux
densities. Again, a potential weakness is that the pixels are not independent (there is the effect of the beam).
Additionally, the assumption of a single line describing a core+jet morphology may not be accurate for highly
resolved sources.
In Fig. 7 we show the comparison between the Largest linear size, the Fitting the radio image, and the DIFMAP methods.
Reassuringly, we find that the three methods provide consistent results. We note that the scatter of the points around
the bisector of the plot is smaller than the errorbars: this is likely caused by the relatively large uncertainties that we
assigned to the Largest linear size and the Fitting the radio image methods being conservatively overestimated. We
decided to continue the analysis with the DIFMAP results because of its advantages: first, the beam shape is taken into
account when fitting components to the visibilities; second, the DIFMAP method does not rely on cleaned images where
pixel-scale artifacts may be present, as it works in the uv-domain.
B. INSIGHTS FROM VLBA DATA AT OTHER FREQUENCIES
Three sources in our sample are VLBA calibrators2
, meaning that there are archival snapshot observations at
multiple frequencies other than 5 GHz. These are 4C+55.16 (2.3 GHz and 7.6 GHz), RXC J1558.3-1410 (2.3 GHz and
8.7 GHz), and Abell 3581 (8.7 GHz). We used the archival observations of these three systems to validate our method
of measuring Φ⊥LOS from the 5 GHz maps. In practice, we applied the same fitting procedure in DIFMAP described
in Sect. 4. The left panel of Fig. 8 shows the results. It is clear that our measurements of Φ⊥LOS are consistent
2 https://obs.vlba.nrao.edu/cst/, Charlot et al. (2020).
17. 17
Figure 7. Comparison between the three methods we tested to measure the position angle of the radio jet in the plane of the
sky (Ψ⊥LOS). In the three panels, the black line represents the bisector of the plot and not a fit to the points. See Appendix A
for details.
between the different frequencies, thus strengthening our results. Radical changes in jet position angle with frequency
are known (e.g., Issaoun et al. 2022), but these are typically found when not only the frequency but also the observed
spatial scales change (e.g. from the parsec to the tens of parsecs scales). As the VLBA data at different frequencies
probe relatively similar scales, it is likely that the observations used in this work do not suffer from this effect.
It is interesting to discuss the case of RXC J1558.3-1410, which unveils a limitation of our work in terms of angle w.r.t.
the line of sight, Φ∥LOS. For this AGN, the data at 8.7 GHz reveal a bright, unresolved component (labeled ’C’) that is
undetected at 5 GHz (see Fig. 8, right panel). If this component was a knot of the jet with a relatively steep spectral
index (α ≤ −0.5), it should have been detectable at 5 GHz. Its non-detection suggests that it may be characterized
by an inverted spectral index (α ≥ 0), which is typical of the synchrotron self-absorbed cores of compact radio sources
(e.g., Sadler 2016). While from the 5 GHz data alone we identified the core of the AGN as the brightest component,
it is likely that the true core is located, in fact, between the two components detected at 5 GHz. While this is not an
issue when measuring Φ⊥LOS, as the whole structure remains aligned, it biases our measurement of Φ∥LOS. Indeed,
using the 5 GHz data alone we would mis-classify the jet and the counter-jet in this system. Component A in the
5 GHz map, previously classified as the core, has to be considered as the jet, while component B, previously classified
as jet, is in fact the counter-jet. Incidentally, for RXC 1558.3-1410, the old and new Φ∥LOS remain consistent with
each other (changing from 39.8◦
± 11.8◦
to 25.1◦
± 6.7◦
). However, this system highlights a limitation that may affect
our measurements of Φ∥LOS, especially for one-sided sources. We verified the absence of an hidden core in all the
other objects of our sample with available archival data at high frequency. For the remaining one-sided sources in our
sample (ClG J1532+3021, Abell 478, Abell 1664, NGC 6338, IC 1262, and NGC 5098) no data at other frequencies
exist, but we plan to observe them with deeper and multi-frequency VLBA observations in the future.
Ultimately, we note that we are currently unable to measure the spectral index of the different components, which
would benefit their classification as jets or core. The available multi-frequency data were not acquired close in time,
meaning that flux variability at parsec scales could strongly bias the results of any spectral index study. Obtaining
coeval multifrequency observations of our sample is a future perspective of this work.
C. RXC J1558.3-1410: X-RAY MORPHOLOGICAL ANALYSIS
As reported in the main text, RXC J1558.3-1410 lacks a dedicated X-ray study of the ICM morphology. To verify the
existence of X-ray cavities in this system, we inspected both the Chandra 0.5 – 2 keV counts image and the residual
image. In both of them, a depression in surface brightness is visible east of the center (see Fig. 9). The depression is
nearly circular, and it is located at ∼ 20′′
= 36 kpc from the center. The signal-to-noise ratio (SNR) of this feature
was measured in the Chandra counts image by comparing the number of net counts within this region, Cc, with the
average number of counts in similar regions with the same size at the same distance from the center, Cs, through the
following expression:
SNR =
|Cc − Cs|
√
Cc + Cs
(C1)
18. 18
RXC J1558.3-1410
8.7 GHz
RXC J1558.3-1410
5 GHz
A
B
A
B
C
RXC J1558.3-1410
8.7 GHz
RXC J1558.3-1410
5 GHz
A
B
A
B
C
Figure 8. Left panel: comparison between Φ⊥LOS at 5 GHz and Φ⊥LOS measured at other frequencies for the sources in our
sample that are VLBA calibrators. The dashed line shows the y = x bisector. Right panel: VLBA images of RXC J1558.3-1410
at 8.7 GHz and at 5 GHz. The components identified in DIFMAP are labeled.
For the depression shown in Fig. 9 (left panel) we measure a SNR = 4.8 (with Cc = 892 and Cs = 1107), which allows us
to identify the feature as a reliable structure. Other depressions that are visible in the residual image do not represent
statistically significant drops in the counts image (either they represent small deficits, around 5%, or the SNR is lower
than 3). Furthermore, we note that based on archival VLA data at 1.4 GHz (see http://www.vla.nrao.edu/astro/nvas/)
there is evidence for radio emission extended towards this depression. This supports the classification of the X-ray
depression as an AGN-inflated cavity in the ICM.
We also note that on larger scales, the surface brightness distribution has a spiral morphology, with a bright edge west
and south-west of the center (see Fig. 9, right panel). This is typical of clusters experiencing sloshing of the hot gas,
which is thus likely present also in RXC J1558.3-1410. The spiral structure is wrapped around the cluster core, and
is visible up to a distance of ∼100 kpc from the center.
30’’ ~ 50 kpc 60’’ ~ 110 kpc
Figure 9. Chandra images of RXC J1558.3-1410. Left panel: 0.5 – 2 keV counts image, smoothed with a Gaussian of kernel
size 3′′
. Green contours are the 1.4 GHz radio emission seen in archival VLA data, starting from 3 ×σ (with σ = 0.4 mJy/beam,
resolution of 2′′
) and increasing in steps of 2. Right panel: residual Chandra image, smoothed with a Gaussian of kernel size
5′′
. Cyan arrows show the spiral morphology of the ICM. In both panels, the green dashed circle shows the identified X-ray
cavity, while the red cross shows the position of the central AGN.
19. 19
D. RADIO DATA AND DIFMAP RESULTS
In this Appendix we present the results of fitting the VLBA data for our sample in DIFMAP. Tab. 3 reports, for
each system, the properties of the radio image shown in Fig. 2 and the parameters of the components used to fit the
visibilities in the uv-domain.
E. COMMENTS ON INDIVIDUAL SOURCES
Abell 2390: galaxy cluster at z = 0.23. The VLBA image shows a two-sided jet structure in the north-south direction,
predominantly in the plane of the sky (consistent with Augusto et al. 2006). From the X-ray point of view, no unique
view on the presence of cavities in this system is present in the literature. From a heavily smoothed and filtered image,
Sonkamble et al. (2015) identified a total of 4 X-ray cavities surrounding the central AGN. From our re-analysis of the
X-ray data (using all the three available ObsIDs) we find compelling evidence for the existence of one of the X-ray
cavities identified by Sonkamble et al. (2015), west of the radio core. Additionally, there are large X-ray cavities east –
west of the core, at a distance from the center of ∼200 kpc (see Lima Neto Ulmer 2011). These structures are filled
by radio emission in the form of large lobes in LOFAR images (see Bı̂rzan et al. 2020). Between the two generations
of X-ray cavities and the inner jets we find a misalignment of almost 90◦
, with projection effects playing at most a
minor role.
ClG J1532+3021: galaxy cluster at z = 0.362 studied by Hlavacek-Larrondo et al. (2013b), who revealed the
presence of sloshing motions and X-ray cavities. Two X-ray cavities are clearly visible east – west of the radio core
in the Chandra image. The VLBA observations reveal a relatively faint source with a small one-sided jet west of the
core, nearly aligned with the X-ray cavities.
• 4C+55.16: galaxy cluster at z=0.242. Hlavacek-Larrondo et al. (2011) discovered two X-ray cavities on opposite
sides of the radio core. The authors noted a surface brightness edge, interpreted as a cold front, south of the cluster’s
center. Whyborn et al. (1985) revealed a pair of radio lobes in the southeast – northwest direction, that coincide with
the X-ray cavities. On VLBA scales we find resolved extended emission that is well fitted in DIFMAP by two components,
that we identify as the core and a jet. Such interpretation is consistent with the EVN images at 5 GHz published by
Whyborn et al. (1985). The northwest cavity is aligned with the radio jet, while the southeast one is misaligned. It is
important to note that projection effects may be relatively important in this system, where Ψ∥LOS ∼ 60◦
.
Abell 478: galaxy cluster at z = 0.088. Sun et al. (2003) and Giacintucci et al. (2014) reported the presence of small
X-ray cavities in the north – south direction, and the disturbed state of the cluster. From the VLBA data we recover
a one-sided source, misaligned by ∼35◦
from the X-ray cavities. The source has a jet-counterjet ratio of roughly 6.
Thus, projection effects may be important in this system. Overall, given the mild difference in P.A. between jet and
X-ray cavities, and projection effects, it is unclear whether this system can be classified as aligned or misaligned.
RX J1447.4+0827: galaxy cluster at z = 0.376. The presence of small X-ray cavities and sloshing signatures in
this object has been reported by Prasow-Émond et al. (2020). On VLBA scales, the source is clearly resolved in a
two-sided structure oriented northwest – southeast. The jets are aligned with the cavities on larger scales, and the low
jet – counterjet ratio (1.1) indicates that projection effects are likely negligible.
Abell 1664: galaxy cluster at z = 0.128. Calzadilla et al. (2019), revealed the presence of two pairs of X-ray cavities
(the inner pair in the east – west direction, the outer pair in the southeast – northwest direction), and of a disturbed
ICM. The VLBA data are difficult to interpret: there is extended, diffuse emission south of the brightest component,
however its morphology is not straightforwardly reminiscent of a jet. By interpreting the radio source as a core + jet
system, the position angle of the AGN jet is misaligned w.r.t. the cavities. The source is also apparently one-sided,
with an angle w.r.t. the line of sight of ∼ 50◦
.
RXC J1558.3-1410: galaxy cluster at z=0.097. As no dedicated studies of the Chandra observations of this object
exist in the literature, we analyzed the data (see Appendix C). We identify a cavity southeast of the AGN (the
depression is significant at a signal-to-noise ratio of SNR=6). We also identify a positive residual spiral from the
residual Chandra image, that we attribute to sloshing of the ICM. Archival VLA observations at 1.4 GHz reveal a
jet feature headed towards the depression, supporting its cavity classification. Being a VLBA calibrator, this radio
galaxy has multi-frequency coverage in the archive. An inspection of the 8.7 GHz observations reveals a two-sided
source. Based on the 5 GHz observations only, the brightest component (A) may be misinterpreted as the radio core.
However, the 8.7 GHz map reveals a third component left of the brightest one. This third component is likely the true
core, self-absorbed (thus invisible) at lower frequencies (see Appendix B for details).
ZwCl 8276: galaxy cluster at z = 0.076. Several structures in the ICM support the idea that the cluster is experiencing
20. 20
Table 3. Properties of the VLBA images shown in Fig. 2 and results of fitting the visibilities in DIFMAP. (1) Name of the
system; (2) size and position angle (from the north axis) of the restoring beam; (3) noise of the VLBA image; (4 – 10) DIFMAP
results: label of the component, flux density, distance from phase center (polar coordinates), angle from the phase center (polar
coordinates, with θ starting from the north axis), major semi-axis, axes ratio, orientation of the component (from the north
axis). When a = 0 the component is a δ-function. When b/a = 1 the component is a circle. When a ̸= 0 and b/a ̸= 1 the
component is an ellipse with orientation ψ.
Cluster Beam, PA σ Comp. Flux r θ a b/a ψ
[mas×mas, ◦
] [mJy/beam] [mJy] [mas] [deg] [mas] [deg]
Abell 2390 3.5 × 1.2, 0.6 0.1 A 118 0.002 -160.2 0 1.0 -8.3
B 7.6 4.68 178.6 1.2 1.0 0
C 57.5 3.43 -7.0 0 1.0 0
D 22.8 22.2 -24.1 14.9 1.0 0
ClG J1532+3021 5.0 × 1.4, 25.1 0.05 A 6.2 11.40 108.5 0 1.0 0
B 1.5 8.59 117.8 1.8 1.0 0
4C+55.16 3.5 × 1.7, 4.4 5.0 A 2136 0.67 83.1 0 1.0 0
B 1561 1.58 -64.3 8.4 0.37 -51.6
Abell 478 4.0 × 1.6, 11.4 0.05 A 5.4 11.21 106.4 0.8 1.0 0
B 0.9 14.28 117.6 0 1.0 0
RX J1447.4+0827 3.2 × 1.1, -6.0 0.05 A 8.1 86.69 84.7 0.4 1.0 0
B 5.6 86.11 83.2 0.6 1.0 0
C 3.8 87.39 86.0 1.0 1.0 0
Abell 1664 3.3 × 1.0, -3.6 0.05 A 9.5 500.45 144.5 0 1.0 0
B 2.5 503.46 144.9 1.3 1.0 0
RXC J1558.3-1410 3.5 × 1.2, 0.5 1.5 A 287 0.04 -24.0 1.2 1.0 0
B 117 7.74 63.9 1.2 1.0 0
ZwCl 8276 3.5 × 1.2, -9.0 0.08 A 72.8 0.11 -11.4 0 1.0 0
B 5.6 1.67 -3.2 0 1.0 0
C 15.7 1.09 174.8 0 1.0 0
Abell 496 3.6 × 1.2, 1.5 0.06 A 44.3 69.49 29.3 0.7 1.0 0
B 7.3 74.79 30.6 0 1.0 0
C 5.3 62.84 28.5 0 1.0 0
ZwCl 235 3.3 × 1.2, -1.9 0.07 A 16.0 65.54 -145.5 0.7 1.0 0
B 3.6 64.36 -146.0 1.2 1.0 0
C 5.3 66.63 -145.0 1.2 1.0 0
Abell 2052 3.3 × 1.2, 1.9 1.7 A 267 0.03 72.6 0.6 1.0 0
B 64.5 4.56 170.8 1.9 1.0 0
C 57.5 4.06 -17.2 1.9 1.0 0
Abell 3581 4.1 × 1.2, 0.6 0.3 A 99.2 0.04 -22.5 0.8 1.0 0
B 128 0.34 58.5 4.8 1.0 0
C 35.6 7.25 . 97.9 3.0 1.0 0
NGC 6338 4.3 × 1.3, -10.6 0.1 A 19.9 0.09 1.8 0.8 1.0 0
B 5.3 4.12 -155.8 3.1 1.0 0
IC 1262∗
5.3 × 3.8, -11.9 0.04 A 3.1 395.39 117.8 0.7 1.0 0
B 0.3 397.27 118.9 4.2 1.0 0
NGC 5098 5.0 × 1.6, 15.5 0.05 A 4.7 34.19 35.6 1.7 1.0 0
B 1.1 33.12 39.2 0.7 1.0 0
NGC 5044 3.9 × 1.3, -4.4 0.03 A 16.5 147.03 -67.8 1.9 1.0 0
B 4.8 150.99 -70.5 6.6 1.0 0
C 0.8 149.64 -64.5 0 1.0 0
Note—∗
The radio map has been created by applying an uv-taper of 30 Mλ to the visibilities.
sloshing (see Ettori et al. (2013)); X-ray cavities (in the north – south direction) have been identified by Ettori et al.
(2013). From our Chandra images, and guided by the recent LOFAR observations of this cluster (Bı̂rzan et al. 2020),
21. 21
we identify a third, outer and larger X-ray cavity northeast of the AGN. In the VLBA images there are compelling
evidence for barely resolved north – south extensions, aligned with the inner X-ray cavities.
Abell 496: galaxy cluster at z = 0.033. Several studies have focused on the dynamical status of the ICM in this
object, given the clear sloshing spiral visible in X-ray observations (e.g., Roediger et al. (2012); Ghizzardi et al. (2014)).
However, no dedicated studies on AGN feedback in this system are available, despite the clear presence of multiple,
aligned X-ray cavities in the northeast – southwest direction, coincident with extended radio emission from the central
AGN (see Giacintucci 2016; Giacintucci et al. in prep.). The VLBA data reveal a two-sided structure in the same
direction, suggesting that over 3 cycles of radio activity the AGN’s jet axis has remained nearly constant. From the
jet-counterjet ratio we exclude that projection effects play a major role.
ZwCl 235: galaxy cluster at z = 0.083. Ubertosi et al. (2023b) revealed two radio-filled cavities in the core of the
cluster oriented in the northeast – southwest direction, and of a sloshing spiral wrapped around the core. The VLBA
data unveil a two-sided radio source nearly aligned with the X-ray cavities, mainly in the plane of the sky.
Abell 2052: well-studied galaxy cluster at z = 0.035. The ICM in this object shows multiple X-ray cavities and
shock fronts around the central AGN, signals of multiple outbursts of the radio galaxy (see Blanton et al. (2011) and
references therein). The two pairs of X-ray cavities are roughly oriented in the north-south direction. The VLBA
reveal a two-sided source extended in the north-south direction. The position angle of the jets is consistent with the
results obtained from multifrequency imaging by Venturi et al. (2004). Overall, the jets and the cavities are roughly
aligned in this system, where projection effects are likely negligible.
Abell 3581: galaxy group at z=0.022. Johnstone et al. (2005); Canning et al. (2013) reported the presence of a
sloshing ICM spiral wrapped around the core and two clear cavities east – west of the central AGN, filled by the radio
lobes of the radio galaxy. A third X-ray cavity is found beyond the west cavity and roughly aligned with the inner
pair. From the VLBA data (5 GHz and 8.7 GHz) we observe a strongly one-sided source, with a core-jet morphology
in the east-west direction, in good agreement with the position of the X-ray cavities.
NGC 6338: merging galaxy group at z=0.027. The multifrequency study of this object has been carried out by
O’Sullivan et al. (2019), who found radio-filled X-ray cavities in both groups. For our analysis we focus on the
southern, larger subgroup, that has two inner X-ray cavities oriented northeast – southwest, and at least one X-ray
cavity on larger scales, west of the core (see also Bı̂rzan et al. 2020; Schellenberger et al. 2023). The VLBA data
reveal a core + jet morphology. The source appears one-sided, although at a level of 3σ (∼0.4 mJy/beam) there are
indications for a counterjet. The radio source is oriented northeast – southwest, thus being aligned with the inner
X-ray cavities but misaligned w.r.t. the older, outer outburst.
IC 1262: galaxy group at z = 0.033. The hot gas in this object shows several substructures (ripples, edges and
depressions). There are two inner X-ray cavities (oriented north –south) and an outer, larger X-ray cavity south of the
center (see Pandge et al. 2019). The VLBA data reveal an extended feature south of the core, that is recovered only
by tapering the visibilities during imaging. The position angle of the jet is in relatively good agreement with that of
the inner and outer X-ray cavities.
NGC 5098: galaxy group at z=0.036. Randall et al. (2009) reported the presence of two X-ray cavities filled by
radio emission and mainly oriented in the north – south direction. The group also shows signs of minor merger with
a galaxy, that is causing sloshing of the IGrM. On VLBA scales we find a core dominated source with a small jet
southeast of the core, nearly aligned with the X-ray cavities.
NGC 5044: well-studied galaxy group at z=0.009. Several works reported the presence of multiple X-ray cavities in
the intragroup medium of this object, with the different pairs approximately aligned along the southeast – northwest
direction (see Schellenberger et al. 2021 and references therein). The VLBA data reveal a two-sided core-jet structure
rotated by ∼90◦
with respect to the successive cavity pairs (see also Schellenberger et al. 2021). Based on the jet-
counterjet ratio the inner jets, the difference in position angle of the jets and the cavities is real and not strongly
influenced by projection effects.
REFERENCES
Alcorn, L. Y., Yee, H. K. C., Drissen, L., et al. 2023,
MNRAS, 522, 1521, doi: 10.1093/mnras/stad948
Arzoumanian, Z., Baker, P. T., Brazier, A., et al. 2021,
ApJ, 914, 121, doi: 10.3847/1538-4357/abfcd3
Astropy Collaboration, Robitaille, T. P., Tollerud, E. J.,
et al. 2013, AA, 558, A33,
doi: 10.1051/0004-6361/201322068
22. 22
Astropy Collaboration, Price-Whelan, A. M., Sipőcz, B. M.,
et al. 2018, AJ, 156, 123, doi: 10.3847/1538-3881/aabc4f
Augusto, P., Edge, A. C., Chandler, C. J. 2006, MNRAS,
367, 366, doi: 10.1111/j.1365-2966.2005.09965.x
Babul, A., Sharma, P., Reynolds, C. S. 2013, ApJ, 768,
11, doi: 10.1088/0004-637X/768/1/11
Bardeen, J. M., Petterson, J. A. 1975, ApJL, 195, L65,
doi: 10.1086/181711
Battye, R. A., Browne, I. W. A. 2009, MNRAS, 399,
1888, doi: 10.1111/j.1365-2966.2009.15429.x
Bi, S., Feng, H., Ho, L. C. 2020, ApJ, 900, 124,
doi: 10.3847/1538-4357/aba761
Biava, N., Brienza, M., Bonafede, A., et al. 2021, AA,
650, A170, doi: 10.1051/0004-6361/202040063
Bı̂rzan, L., Rafferty, D. A., McNamara, B. R., Wise,
M. W., Nulsen, P. E. J. 2004, ApJ, 607, 800,
doi: 10.1086/383519
Bı̂rzan, L., Rafferty, D. A., Brüggen, M., et al. 2020,
MNRAS, 496, 2613, doi: 10.1093/mnras/staa1594
Blandford, R. D., Znajek, R. L. 1977, MNRAS, 179, 433,
doi: 10.1093/mnras/179.3.433
Blanton, E. L., Randall, S. W., Clarke, T. E., et al. 2011,
ApJ, 737, 99, doi: 10.1088/0004-637X/737/2/99
Brighenti, F., Mathews, W. G. 2006, ApJ, 643, 120,
doi: 10.1086/502645
Brüggen, M., Scannapieco, E., Heinz, S. 2009, MNRAS,
395, 2210, doi: 10.1111/j.1365-2966.2009.14684.x
Burke, D., Laurino, O., Wmclaugh, et al. 2021,
sherpa/sherpa: Sherpa 4.14.0, 4.14.0, Zenodo, Zenodo,
doi: 10.5281/zenodo.5554957
Calzadilla, M. S., Russell, H. R., McDonald, M. A., et al.
2019, ApJ, 875, 65, doi: 10.3847/1538-4357/ab09f6
Canning, R. E. A., Sun, M., Sanders, J. S., et al. 2013,
MNRAS, 435, 1108, doi: 10.1093/mnras/stt1345
Cao, X. 2000, AA, 355, 44,
doi: 10.48550/arXiv.astro-ph/0001168
Cavagnolo, K. W., McNamara, B. R., Wise, M. W., et al.
2011, ApJ, 732, 71, doi: 10.1088/0004-637X/732/2/71
Charlot, P., Jacobs, C. S., Gordon, D., et al. 2020, AA,
644, A159, doi: 10.1051/0004-6361/202038368
Chon, G., Böhringer, H., Krause, M., Trümper, J. 2012,
AA, 545, L3, doi: 10.1051/0004-6361/201219538
Churazov, E., Forman, W., Jones, C., Böhringer, H. 2000,
AA, 356, 788, doi: 10.48550/arXiv.astro-ph/0002375
Czerny, B., You, B. 2016, Astronomische Nachrichten,
337, 73, doi: 10.1002/asna.201512268
Deller, A. T., Weisberg, J. M., Nice, D. J., Chatterjee, S.
2018, ApJ, 862, 139, doi: 10.3847/1538-4357/aacf95
Donahue, M., Voit, G. M. 2022, PhR, 973, 1,
doi: 10.1016/j.physrep.2022.04.005
Dunn, R. J. H., Fabian, A. C., Taylor, G. B. 2005,
MNRAS, 364, 1343,
doi: 10.1111/j.1365-2966.2005.09673.x
Dupke, R., White, R. E., I. 2002, in Astronomical
Society of the Pacific Conference Series, Vol. 262, The
High Energy Universe at Sharp Focus: Chandra Science,
ed. E. M. Schlegel S. D. Vrtilek, 377,
doi: 10.48550/arXiv.astro-ph/0110070
Eckert, D., Gaspari, M., Gastaldello, F., Le Brun, A. M. C.,
O’Sullivan, E. 2021, Universe, 7, 142,
doi: 10.3390/universe7050142
Enßlin, T. A., Heinz, S. 2002, AA, 384, L27,
doi: 10.1051/0004-6361:20020207
Ettori, S., Gastaldello, F., Gitti, M., et al. 2013, AA, 555,
A93, doi: 10.1051/0004-6361/201321107
Fabian, A. C. 2012, ARAA, 50, 455,
doi: 10.1146/annurev-astro-081811-125521
Fabian, A. C., Reynolds, C. S., Taylor, G. B., Dunn,
R. J. H. 2005, MNRAS, 363, 891,
doi: 10.1111/j.1365-2966.2005.09484.x
Falceta-Gonçalves, D., Caproni, A., Abraham, Z., Teixeira,
D. M., de Gouveia Dal Pino, E. M. 2010, ApJL, 713,
L74, doi: 10.1088/2041-8205/713/1/L74
Fruscione, A., McDowell, J. C., Allen, G. E., et al. 2006, in
Society of Photo-Optical Instrumentation Engineers
(SPIE) Conference Series, Vol. 6270, Society of
Photo-Optical Instrumentation Engineers (SPIE)
Conference Series, ed. D. R. Silva R. E. Doxsey,
62701V, doi: 10.1117/12.671760
Garofalo, D., Joshi, R., Yang, X., et al. 2020, ApJ, 889, 91,
doi: 10.3847/1538-4357/ab64e3
Gaspari, M., Brighenti, F., Temi, P. 2015, AA, 579,
A62, doi: 10.1051/0004-6361/201526151
Gaspari, M., Temi, P., Brighenti, F. 2017, MNRAS, 466,
677, doi: 10.1093/mnras/stw3108
Ghisellini, G., Celotti, A. 2001, Astronomy
Astrophysics, 379, L1
Ghizzardi, S., De Grandi, S., Molendi, S. 2014, AA,
570, A117, doi: 10.1051/0004-6361/201424016
Giacintucci, S. 2016, in Mid-Atlantic Radio-Loud AGN
Meeting (MARLAM).
https://astro.umbc.edu/MARLAM2016/presentations/
/Giacintucci Simona MARLAM4 2016.pdf
Giacintucci, S., Markevitch, M., Johnston-Hollitt, M., et al.
2020, ApJ, 891, 1, doi: 10.3847/1538-4357/ab6a9d
Giacintucci, S., Markevitch, M., Venturi, T., et al. 2014,
ApJ, 781, 9, doi: 10.1088/0004-637X/781/1/9
23. 23
Giovannini, G., Casadio, C., Giroletti, M., et al. 2011, in
Jets at All Scales, ed. G. E. Romero, R. A. Sunyaev,
T. Belloni, Vol. 275, 150–154,
doi: 10.1017/S174392131001584X
Giri, G., Vaidya, B., Rossi, P., et al. 2022, AA, 662, A5,
doi: 10.1051/0004-6361/202142546
Giroletti, M., Giovannini, G., Feretti, L., et al. 2004, ApJ,
600, 127, doi: 10.1086/379663
Gitti, M., Brighenti, F., McNamara, B. R. 2012,
Advances in Astronomy, 2012, 950641,
doi: 10.1155/2012/950641
Gitti, M., O’Sullivan, E., Giacintucci, S., et al. 2010, ApJ,
714, 758, doi: 10.1088/0004-637X/714/1/758
Greisen, E. W. 2003, in Astrophysics and Space Science
Library, Vol. 285, Information Handling in Astronomy -
Historical Vistas, ed. A. Heck, 109,
doi: 10.1007/0-306-48080-8 7
Harris, C. R., Millman, K. J., van der Walt, S. J., et al.
2020, Nature, 585, 357, doi: 10.1038/s41586-020-2649-2
Hlavacek-Larrondo, J., Fabian, A. C., Edge, A. C., et al.
2013a, MNRAS, 431, 1638, doi: 10.1093/mnras/stt283
Hlavacek-Larrondo, J., Fabian, A. C., Sanders, J. S.,
Taylor, G. B. 2011, MNRAS, 415, 3520,
doi: 10.1111/j.1365-2966.2011.18960.x
Hlavacek-Larrondo, J., Allen, S. W., Taylor, G. B., et al.
2013b, ApJ, 777, 163, doi: 10.1088/0004-637X/777/2/163
Hlavacek-Larrondo, J., McDonald, M., Benson, B. A., et al.
2015, ApJ, 805, 35, doi: 10.1088/0004-637X/805/1/35
Hogan, M. T. 2014, PhD thesis, Durham University, UK
Hogan, M. T., Edge, A. C., Geach, J. E., et al. 2015a,
MNRAS, 453, 1223, doi: 10.1093/mnras/stv1518
Hogan, M. T., Edge, A. C., Hlavacek-Larrondo, J., et al.
2015b, MNRAS, 453, 1201, doi: 10.1093/mnras/stv1517
Hudson, D. S., Reiprich, T. H., Clarke, T. E., Sarazin,
C. L. 2006, AA, 453, 433,
doi: 10.1051/0004-6361:20064955
Huško, F., Lacey, C. G., Schaye, J., Schaller, M., Nobels,
F. S. J. 2022, MNRAS, 516, 3750,
doi: 10.1093/mnras/stac2278
Issaoun, S., Wielgus, M., Jorstad, S., et al. 2022, ApJ, 934,
145, doi: 10.3847/1538-4357/ac7a40
Johnstone, R. M., Fabian, A. C., Morris, R. G., Taylor,
G. B. 2005, MNRAS, 356, 237,
doi: 10.1111/j.1365-2966.2004.08445.x
Joshi, R., Krishna, G., Yang, X., et al. 2019, ApJ, 887, 266,
doi: 10.3847/1538-4357/ab536f
Kharb, P., Lister, M. L., Cooper, N. J. 2010, ApJ, 710,
764, doi: 10.1088/0004-637X/710/1/764
King, A., Nixon, C. 2015, MNRAS, 453, L46,
doi: 10.1093/mnrasl/slv098
Kolokythas, K., O’Sullivan, E., Giacintucci, S., et al. 2020,
MNRAS, 496, 1471, doi: 10.1093/mnras/staa1506
Lalakos, A., Gottlieb, O., Kaaz, N., et al. 2022, ApJL, 936,
L5, doi: 10.3847/2041-8213/ac7bed
Lima Neto, G., Ulmer, M. 2011, in The X-ray Universe
2011, ed. J.-U. Ness M. Ehle, 241
Liska, M., Hesp, C., Tchekhovskoy, A., et al. 2018,
MNRAS, 474, L81, doi: 10.1093/mnrasl/slx174
Liu, F. K. 2004, MNRAS, 347, 1357,
doi: 10.1111/j.1365-2966.2004.07325.x
Machalski, J., Jamrozy, M., Stawarz, L., Weżgowiec, M.
2016, AA, 595, A46, doi: 10.1051/0004-6361/201629249
Mathews, W. G., Brighenti, F. 2003, ARAA, 41, 191,
doi: 10.1146/annurev.astro.41.090401.094542
McCarthy, P. J., van Breugel, W., Kapahi, V. K. 1991,
ApJ, 371, 478, doi: 10.1086/169911
McKinney, J. C., Tchekhovskoy, A., Blandford, R. D.
2013, Science, 339, 49, doi: 10.1126/science.1230811
McNamara, B. R., Nulsen, P. E. J. 2007, ARAA, 45,
117, doi: 10.1146/annurev.astro.45.051806.110625
—. 2012, New Journal of Physics, 14, 055023,
doi: 10.1088/1367-2630/14/5/055023
Meier, D. L. 2001, ApJL, 548, L9, doi: 10.1086/318921
Mezcua, M., Hlavacek-Larrondo, J., Lucey, J. R., et al.
2018, MNRAS, 474, 1342, doi: 10.1093/mnras/stx2812
Morris, M., Wilcots, E., Hooper, E., Heinz, S. 2022, in
American Astronomical Society Meeting Abstracts,
Vol. 54, American Astronomical Society Meeting #240,
101.24
Mroczkowski, T., Donahue, M., van Marrewijk, J., et al.
2022, AA, 665, A48, doi: 10.1051/0004-6361/202243718
Narayan, R., Yi, I. 1995, ApJ, 452, 710,
doi: 10.1086/176343
O’Sullivan, E., David, L. P., Vrtilek, J. M. 2014,
MNRAS, 437, 730, doi: 10.1093/mnras/stt1926
O’Sullivan, E., Schellenberger, G., Burke, D. J., et al. 2019,
MNRAS, 488, 2925, doi: 10.1093/mnras/stz1711
O’Sullivan, E., Worrall, D. M., Birkinshaw, M., et al. 2011,
MNRAS, 416, 2916,
doi: 10.1111/j.1365-2966.2011.19239.x
Palimaka, J. J., Bridle, A. H., Fomalont, E. B., Brandie,
G. W. 1979, ApJL, 231, L7, doi: 10.1086/182995
Pandge, M. B., Sonkamble, S. S., Parekh, V., et al. 2019,
ApJ, 870, 62, doi: 10.3847/1538-4357/aaf105
Paterno-Mahler, R., Blanton, E. L., Randall, S. W.,
Clarke, T. E. 2013, ApJ, 773, 114,
doi: 10.1088/0004-637X/773/2/114
Pearson, T. J., Readhead, A. C. S. 1988, ApJ, 328, 114,
doi: 10.1086/166274
24. 24
Piffaretti, R., Arnaud, M., Pratt, G. W., Pointecouteau, E.,
Melin, J. B. 2011, AA, 534, A109,
doi: 10.1051/0004-6361/201015377
Prasow-Émond, M., Hlavacek-Larrondo, J., Rhea, C. L.,
et al. 2020, AJ, 160, 103, doi: 10.3847/1538-3881/ab9ff3
Randall, S. W., Clarke, T. E., Nulsen, P. E. J., et al. 2010,
ApJ, 722, 825, doi: 10.1088/0004-637X/722/1/825
Randall, S. W., Jones, C., Markevitch, M., et al. 2009, ApJ,
700, 1404, doi: 10.1088/0004-637X/700/2/1404
Randall, S. W., Nulsen, P. E. J., Jones, C., et al. 2015,
ApJ, 805, 112, doi: 10.1088/0004-637X/805/2/112
Robitaille, T., Bressert, E. 2012, APLpy: Astronomical
Plotting Library in Python, Astrophysics Source Code
Library, record ascl:1208.017. http://ascl.net/1208.017
Roediger, E., Lovisari, L., Dupke, R., et al. 2012, MNRAS,
420, 3632, doi: 10.1111/j.1365-2966.2011.20287.x
Rubinur, K., Das, M., Kharb, P. 2018, Journal of
Astrophysics and Astronomy, 39, 8,
doi: 10.1007/s12036-018-9512-y
Russell, H. R., McNamara, B. R., Edge, A. C., et al. 2013,
MNRAS, 432, 530, doi: 10.1093/mnras/stt490
Sadler, E. M. 2016, Astronomische Nachrichten, 337, 105,
doi: 10.1002/asna.201512274
Schawinski, K., Koss, M., Berney, S., Sartori, L. F. 2015,
MNRAS, 451, 2517, doi: 10.1093/mnras/stv1136
Schellenberger, G., David, L. P., Vrtilek, J., et al. 2021,
ApJ, 906, 16, doi: 10.3847/1538-4357/abc488
Schellenberger, G., O’Sullivan, E., Giacintucci, S., et al.
2023, ApJ, 948, 101, doi: 10.3847/1538-4357/acc52e
Scheuer, P. A. G., Readhead, A. C. S. 1979, Nature, 277,
182, doi: 10.1038/277182a0
Shepherd, M. C., Pearson, T. J., Taylor, G. B. 1994, in
Bulletin of the American Astronomical Society, Vol. 26,
987–989
Singal, A. K. 2016, ApJ, 827, 66,
doi: 10.3847/0004-637X/827/1/66
Soker, N. 2022, Universe, 8, 483,
doi: 10.3390/universe8090483
Sonkamble, S. S., Vagshette, N. D., Pawar, P. K., Patil,
M. K. 2015, ApSS, 359, 21,
doi: 10.1007/s10509-015-2508-z
Su, Y., Nulsen, P. E. J., Kraft, R. P., et al. 2017, ApJ, 851,
69, doi: 10.3847/1538-4357/aa989e
Sun, M., Jones, C., Murray, S. S., et al. 2003, ApJ, 587,
619, doi: 10.1086/368300
Ubertosi, F., Gitti, M., Brighenti, F. 2023a, AA, 670,
A23, doi: 10.1051/0004-6361/202244023
—. 2023b, AA, 670, A23,
doi: 10.1051/0004-6361/202244023
Ubertosi, F., Gitti, M., Brighenti, F., et al. 2021, ApJL,
923, L25, doi: 10.3847/2041-8213/ac374c
Vazquez Najar, L. A., Andernach, H. 2019, arXiv
e-prints, arXiv:1908.09989,
doi: 10.48550/arXiv.1908.09989
Čemeljić, M., Yang, H., Yuan, F., Shang, H. 2022, ApJ,
933, 55, doi: 10.3847/1538-4357/ac70cc
Venturi, T., Dallacasa, D., Stefanachi, F. 2004, AA,
422, 515, doi: 10.1051/0004-6361:20040089
Wehrle, A. E., Unwin, S. C., Aller, H. D., Aller, M. F.,
Nicolson, G. 1996, in Astronomical Society of the Pacific
Conference Series, Vol. 110, Blazar Continuum
Variability, ed. H. R. Miller, J. R. Webb, J. C. Noble,
285
Werner, N., McNamara, B. R., Churazov, E.,
Scannapieco, E. 2019, SSRv, 215, 5,
doi: 10.1007/s11214-018-0571-9
Whyborn, N. D., Browne, I. W. A., Wilkinson, P. N.,
Porcas, R. W., Spinrad, H. 1985, MNRAS, 214, 55,
doi: 10.1093/mnras/214.1.55
Wise, M. W., McNamara, B. R., Nulsen, P. E. J., Houck,
J. C., David, L. P. 2007, ApJ, 659, 1153,
doi: 10.1086/512767
Wu, Q., Cao, X. 2008, ApJ, 687, 156, doi: 10.1086/591933
Zhang, C., Churazov, E., Schekochihin, A. 2019, in
American Astronomical Society Meeting Abstracts, Vol.
233, American Astronomical Society Meeting Abstracts
#233, 438.07
Zou, H., Gao, J., Xu, X., et al. 2021, ApJS, 253, 56,
doi: 10.3847/1538-4365/abe5b0
ZuHone, J. A., Markevitch, M., Weinberger, R., Nulsen, P.,
Ehlert, K. 2021, ApJ, 914, 73,
doi: 10.3847/1538-4357/abf7bc