The collimation of relativistic jets launched from the vicinity of supermassive black holes (SMBHs) at the centers
of active galactic nuclei (AGNs) is one of the key questions to understand the nature of AGN jets. However, little is
known about the detailed jet structure for AGN like quasars since very high angular resolutions are required to
resolve these objects. We present very long baseline interferometry (VLBI) observations of the archetypical quasar
3C 273 at 86 GHz, performed with the Global Millimeter VLBI Array, for the first time including the Atacama
Large Millimeter/submillimeter Array. Our observations achieve a high angular resolution down to ∼60 μas,
resolving the innermost part of the jet ever on scales of ∼105 Schwarzschild radii. Our observations, including
close-in-time High Sensitivity Array observations of 3C 273 at 15, 22, and 43 GHz, suggest that the inner jet
collimates parabolically, while the outer jet expands conically, similar to jets from other nearby low-luminosity
AGNs. We discovered the jet collimation break around 107 Schwarzschild radii, providing the first compelling
evidence for structural transition in a quasar jet. The location of the collimation break for 3C 273 is farther
downstream from the sphere of gravitational influence (SGI) from the central SMBH. With the results for other
AGN jets, our results show that the end of the collimation zone in AGN jets is governed not only by the SGI of the
SMBH but also by the more diverse properties of the central nuclei.
Detecting a disc bending wave in a barred-spiral galaxy at redshift 4.4Sérgio Sacani
The recent discovery of barred spiral galaxies in the early Universe (z > 2) poses questions of how these structures form and
how they influence galaxy evolution in the early Universe. In this study, we investigate the morphology and kinematics of the
far-infrared (FIR) continuum and [C II] emission in BRI1335-0417 at z ≈ 4.4 from ALMA observations. The variations in
position angle and ellipticity of the isophotes show the characteristic signature of a barred galaxy. The bar, 3.3+0.2 −0.2 kpc long in
radius and bridging the previously identified two-armed spiral, is evident in both [C II] and FIR images, driving the galaxy’s rapid
evolution by channelling gas towards the nucleus. Fourier analysis of the [C II] velocity field reveals an unambiguous kinematic
m = 2 mode with a line-of-sight velocity amplitude of up to ∼30–40 km s−1; a plausible explanation is the disc’s vertical bending
mode triggered by external perturbation, which presumably induced the high star formation rate and the bar/spiral structure. The
bar identified in [C II] and FIR images of the gas-rich disc galaxy ( 70 per cent of the total mass within radius R ≈ 2.2 disc
scale lengths) suggests a new perspective of early bar formation in high redshift gas-rich galaxies – a gravitationally unstable
gas-rich disc creating a star-forming gaseous bar, rather than a stellar bar emerging from a pre-existing stellar disc. This may
explain the prevalent bar-like structures seen in FIR images of high-redshift submillimeter galaxies.
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 JWST Discovery of the Triply-imaged Type Ia “Supernova H0pe” and Observat...Sérgio Sacani
A Type Ia supernova (SN) at z = 1.78 was discovered in James Webb Space Telescope Near Infrared
Camera imaging of the galaxy cluster PLCK G165.7+67.0 (G165; z = 0.35). The SN is situated 1.5–
2 kpc from its host galaxy Arc 2 and appears in three different locations as a result of gravitational
lensing by G165. These data can yield a value for Hubble’s constant using time delays from this
multiply-imaged SN Ia that we call “SN H0pe.” Over the entire field we identified 21 image multiplicities,
confirmed five of them using Near-Infrared Spectrograph (NIRspec), and constructed a new
lens model that gives a total mass within 600 kpc of (2.6 ± 0.3) × 1014M⊙. The photometry uncovered
a galaxy overdensity at Arc 2’s redshift. NIRSpec confirmed six member galaxies, four of which
surround Arc 2 with relative velocity ≲900 km s−1 and projected physical extent ≲33 kpc. Arc 2
dominates the stellar mass ((5.0±0.1)×1011M⊙), which is a factor of ten higher than other members
of this compact galaxy group. These other group members have specific star formation rates (sSFR)
arXiv:2309.07326v1 [astro-ph.GA] 13 Sep 2023
2 Frye, Pascale, Pierel et al.
of 2–260 Gyr−1 derived from the Hα-line flux corrected for stellar absorption, dust extinction, and slit
losses. Another group centered on the dusty star forming galaxy Arc 1 is at z = 2.24. The total SFR
for the Arc 1 group (≳400M⊙ yr−1) translates to a supernova rate of ∼1 SNe yr−1, suggesting that
regular monitoring of this cluster may yield additional SNe.
A SPectroscopic Survey of Biased Halos in the Reionization Era (ASPIRE): JWST...Sérgio Sacani
The JWST ASPIRE program discovered a filamentary structure of galaxies around a z=6.61 quasar through spectroscopic observations. Ten [O III] emitters were found clustered along a filament spanning 637 cMpc3, indicating one of the most overdense early structures known. Additional observations revealed a complex environment with both UV-bright and dusty galaxies present, showing that early galaxy evolution was not simultaneous around the quasar. In total 41 [O III] emitters were discovered between 5.3 < z < 6.7, with half clustered at z ~ 5.4 and 6.2, indicating high-redshift star-forming galaxies are generally clustered.
The ALMA Survey of Star Formation and Evolution in Massive Protoclusters with...Sérgio Sacani
The ALMA Survey of Star Formation and Evolution in Massive Protoclusters with Blue Profiles
(ASSEMBLE) aims to investigate the process of mass assembly and its connection to high-mass star
formation theories in protoclusters in a dynamic view. We observed 11 massive (Mclump ≳ 103 M⊙),
luminous (Lbol ≳ 104 L⊙), and blue-profile (infall signature) clumps by ALMA with resolution of
∼2200–5500 au (median value of 3500 au) at 350 GHz (870 µm). 248 dense cores were identified, including 106 cores showing protostellar signatures and 142 prestellar core candidates. Compared to
early-stage infrared dark clouds (IRDCs) by ASHES, the core mass and surface density within the
ASSEMBLE clumps exhibited significant increment, suggesting concurrent core accretion during the
evolution of the clumps. The maximum mass of prestellar cores was found to be 2 times larger than
that in IRDCs, indicating that evolved protoclusters have the potential to harbor massive prestellar
cores. The mass relation between clumps and their most massive core (MMCs) is observed in ASSEMBLE but not in IRDCs, which is suggested to be regulated by multiscale mass accretion. The
mass correlation between the core clusters and their MMCs has a steeper slope compared to that
observed in stellar clusters, which can be due to fragmentation of the MMC and stellar multiplicity.
We observe a decrease in core separation and an increase in central concentration as protoclusters
evolve. We confirm primordial mass segregation in the ASSEMBLE protoclusters, possibly resulting
from gravitational concentration and/or gas accretion.
A Spatially Resolved Analysis of Star Formation Burstiness by Comparing UV an...Sérgio Sacani
The UltraViolet imaging of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey Fields
(UVCANDELS) program provides Hubble Space Telescope (HST)/UVIS F275W imaging for four CANDELS
fields. We combine this UV imaging with existing HST/near-IR grism spectroscopy from 3D-HST+AGHAST to
directly compare the resolved rest-frame UV and Hα emission for a sample of 979 galaxies at 0.7 < z < 1.5,
spanning a range in stellar mass of 108−11.5 Me. Using a stacking analysis, we perform a resolved comparison
between homogenized maps of rest-UV and Hα to compute the average UV-to-Hα luminosity ratio (an indicator of
burstiness in star formation) as a function of galactocentric radius. We find that galaxies below stellar mass of
∼109.5 Me, at all radii, have a UV-to-Hα ratio higher than the equilibrium value expected from constant star
formation, indicating a significant contribution from bursty star formation. Even for galaxies with stellar mass
109.5 Me, the UV-to-Hα ratio is elevated toward their outskirts (R/Reff > 1.5), suggesting that bursty star
formation is likely prevalent in the outskirts of even the most massive galaxies, but is likely overshadowed by their
brighter cores. Furthermore, we present the UV-to-Hα ratio as a function of galaxy surface brightness, a proxy for
stellar mass surface density, and find that regions below ∼107.5 Me kpc−2 are consistent with bursty star formation,
regardless of their galaxy stellar mass, potentially suggesting that local star formation is independent of global
galaxy properties at the smallest scales. Last, we find galaxies at z > 1.1 to have bursty star formation, regardless of
radius or surface brightness.
Exploring the nature and synchronicity of early cluster formation in the Larg...Sérgio Sacani
We analyse Hubble Space Telescope observations of six globular clusters in the Large Magel- lanic Cloud (LMC) from programme GO-14164 in Cycle 23. These are the deepest available observations of the LMC globular cluster population; their uniformity facilitates a precise comparison with globular clusters in the Milky Way. Measuring the magnitude of the main- sequence turn-off point relative to template Galactic globular clusters allows the relative ages of the clusters to be determined with a mean precision of 8.4 per cent, and down to 6 per cent for individual objects. We find that the mean age of our LMC cluster ensemble is identical to the mean age of the oldest metal-poor clusters in the Milky Way halo to 0.2 ± 0.4 Gyr. This provides the most sensitive test to date of the synchronicity of the earliest epoch of globular cluster formation in two independent galaxies. Horizontal branch magnitudes and subdwarf fitting to the main sequence allow us to determine distance estimates for each cluster and examine their geometric distribution in the LMC. Using two different methods, we find an average distance to the LMC of 18.52 ± 0.05.
How to tell an accreting boson star from a black hole h. olivares et al (2020)SOCIEDAD JULIO GARAVITO
Abstract
The tentative evidences for late time “echoes” in LIGO gravitational
waves (GWs) have been claimed to be signatures of horizonless compact
objects rather than vacuum black holes (BHs) possessing horizons. In
general, in the past, many authors have considered the possibility that
the so-called BHs might be only BH mimickers (BHMs). And recently
it has been suggested that the true astrophysical BH having no intrinsic
magnetic fields may be differentiated from magnetized BHMs by studying
the radial variations of magnetic fields around pertinent compact objects
(Lobanov, Nat. Astron. 2017). Here we highlight that close to the surface
of BHMs, the magnetic field pattern differs significantly from the same for
non-relativistic Neutron Stars (B ∼ r −3 ). In particular, we point out that
for ultra- compact BHMs, the polar field is weaker than the equatorial field
1by an extremely large factor of ∼ z s /lnz s , where z s ≫ 1 is the surface
gravitational redshift. We suggest that by studying the of radial variation
as well as such significant asymmetry of magnetic field structure near the
compact object, future observations may differentiate a theoretical black
hole from a astrophysical BH mimicker (a compact object). This study
also shows that even if some BHMs would be hypothesized to possess
magnetic fields even stronger than that of magnetars, in certain cases, they
may effectively behave as atoll type neutron stars possessing extremely low
magnetic fields.
Keywords: X-ray Binaries; Active Galactic Nuclei; Magnetic Field;
Black Hole Mimickers; Relativistic Astrophysics.
PACS numbers: 04.40.Dg, 97.80.Jp, 97.60.Gb, 95.86.Nv.
Detecting a disc bending wave in a barred-spiral galaxy at redshift 4.4Sérgio Sacani
The recent discovery of barred spiral galaxies in the early Universe (z > 2) poses questions of how these structures form and
how they influence galaxy evolution in the early Universe. In this study, we investigate the morphology and kinematics of the
far-infrared (FIR) continuum and [C II] emission in BRI1335-0417 at z ≈ 4.4 from ALMA observations. The variations in
position angle and ellipticity of the isophotes show the characteristic signature of a barred galaxy. The bar, 3.3+0.2 −0.2 kpc long in
radius and bridging the previously identified two-armed spiral, is evident in both [C II] and FIR images, driving the galaxy’s rapid
evolution by channelling gas towards the nucleus. Fourier analysis of the [C II] velocity field reveals an unambiguous kinematic
m = 2 mode with a line-of-sight velocity amplitude of up to ∼30–40 km s−1; a plausible explanation is the disc’s vertical bending
mode triggered by external perturbation, which presumably induced the high star formation rate and the bar/spiral structure. The
bar identified in [C II] and FIR images of the gas-rich disc galaxy ( 70 per cent of the total mass within radius R ≈ 2.2 disc
scale lengths) suggests a new perspective of early bar formation in high redshift gas-rich galaxies – a gravitationally unstable
gas-rich disc creating a star-forming gaseous bar, rather than a stellar bar emerging from a pre-existing stellar disc. This may
explain the prevalent bar-like structures seen in FIR images of high-redshift submillimeter galaxies.
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 JWST Discovery of the Triply-imaged Type Ia “Supernova H0pe” and Observat...Sérgio Sacani
A Type Ia supernova (SN) at z = 1.78 was discovered in James Webb Space Telescope Near Infrared
Camera imaging of the galaxy cluster PLCK G165.7+67.0 (G165; z = 0.35). The SN is situated 1.5–
2 kpc from its host galaxy Arc 2 and appears in three different locations as a result of gravitational
lensing by G165. These data can yield a value for Hubble’s constant using time delays from this
multiply-imaged SN Ia that we call “SN H0pe.” Over the entire field we identified 21 image multiplicities,
confirmed five of them using Near-Infrared Spectrograph (NIRspec), and constructed a new
lens model that gives a total mass within 600 kpc of (2.6 ± 0.3) × 1014M⊙. The photometry uncovered
a galaxy overdensity at Arc 2’s redshift. NIRSpec confirmed six member galaxies, four of which
surround Arc 2 with relative velocity ≲900 km s−1 and projected physical extent ≲33 kpc. Arc 2
dominates the stellar mass ((5.0±0.1)×1011M⊙), which is a factor of ten higher than other members
of this compact galaxy group. These other group members have specific star formation rates (sSFR)
arXiv:2309.07326v1 [astro-ph.GA] 13 Sep 2023
2 Frye, Pascale, Pierel et al.
of 2–260 Gyr−1 derived from the Hα-line flux corrected for stellar absorption, dust extinction, and slit
losses. Another group centered on the dusty star forming galaxy Arc 1 is at z = 2.24. The total SFR
for the Arc 1 group (≳400M⊙ yr−1) translates to a supernova rate of ∼1 SNe yr−1, suggesting that
regular monitoring of this cluster may yield additional SNe.
A SPectroscopic Survey of Biased Halos in the Reionization Era (ASPIRE): JWST...Sérgio Sacani
The JWST ASPIRE program discovered a filamentary structure of galaxies around a z=6.61 quasar through spectroscopic observations. Ten [O III] emitters were found clustered along a filament spanning 637 cMpc3, indicating one of the most overdense early structures known. Additional observations revealed a complex environment with both UV-bright and dusty galaxies present, showing that early galaxy evolution was not simultaneous around the quasar. In total 41 [O III] emitters were discovered between 5.3 < z < 6.7, with half clustered at z ~ 5.4 and 6.2, indicating high-redshift star-forming galaxies are generally clustered.
The ALMA Survey of Star Formation and Evolution in Massive Protoclusters with...Sérgio Sacani
The ALMA Survey of Star Formation and Evolution in Massive Protoclusters with Blue Profiles
(ASSEMBLE) aims to investigate the process of mass assembly and its connection to high-mass star
formation theories in protoclusters in a dynamic view. We observed 11 massive (Mclump ≳ 103 M⊙),
luminous (Lbol ≳ 104 L⊙), and blue-profile (infall signature) clumps by ALMA with resolution of
∼2200–5500 au (median value of 3500 au) at 350 GHz (870 µm). 248 dense cores were identified, including 106 cores showing protostellar signatures and 142 prestellar core candidates. Compared to
early-stage infrared dark clouds (IRDCs) by ASHES, the core mass and surface density within the
ASSEMBLE clumps exhibited significant increment, suggesting concurrent core accretion during the
evolution of the clumps. The maximum mass of prestellar cores was found to be 2 times larger than
that in IRDCs, indicating that evolved protoclusters have the potential to harbor massive prestellar
cores. The mass relation between clumps and their most massive core (MMCs) is observed in ASSEMBLE but not in IRDCs, which is suggested to be regulated by multiscale mass accretion. The
mass correlation between the core clusters and their MMCs has a steeper slope compared to that
observed in stellar clusters, which can be due to fragmentation of the MMC and stellar multiplicity.
We observe a decrease in core separation and an increase in central concentration as protoclusters
evolve. We confirm primordial mass segregation in the ASSEMBLE protoclusters, possibly resulting
from gravitational concentration and/or gas accretion.
A Spatially Resolved Analysis of Star Formation Burstiness by Comparing UV an...Sérgio Sacani
The UltraViolet imaging of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey Fields
(UVCANDELS) program provides Hubble Space Telescope (HST)/UVIS F275W imaging for four CANDELS
fields. We combine this UV imaging with existing HST/near-IR grism spectroscopy from 3D-HST+AGHAST to
directly compare the resolved rest-frame UV and Hα emission for a sample of 979 galaxies at 0.7 < z < 1.5,
spanning a range in stellar mass of 108−11.5 Me. Using a stacking analysis, we perform a resolved comparison
between homogenized maps of rest-UV and Hα to compute the average UV-to-Hα luminosity ratio (an indicator of
burstiness in star formation) as a function of galactocentric radius. We find that galaxies below stellar mass of
∼109.5 Me, at all radii, have a UV-to-Hα ratio higher than the equilibrium value expected from constant star
formation, indicating a significant contribution from bursty star formation. Even for galaxies with stellar mass
109.5 Me, the UV-to-Hα ratio is elevated toward their outskirts (R/Reff > 1.5), suggesting that bursty star
formation is likely prevalent in the outskirts of even the most massive galaxies, but is likely overshadowed by their
brighter cores. Furthermore, we present the UV-to-Hα ratio as a function of galaxy surface brightness, a proxy for
stellar mass surface density, and find that regions below ∼107.5 Me kpc−2 are consistent with bursty star formation,
regardless of their galaxy stellar mass, potentially suggesting that local star formation is independent of global
galaxy properties at the smallest scales. Last, we find galaxies at z > 1.1 to have bursty star formation, regardless of
radius or surface brightness.
Exploring the nature and synchronicity of early cluster formation in the Larg...Sérgio Sacani
We analyse Hubble Space Telescope observations of six globular clusters in the Large Magel- lanic Cloud (LMC) from programme GO-14164 in Cycle 23. These are the deepest available observations of the LMC globular cluster population; their uniformity facilitates a precise comparison with globular clusters in the Milky Way. Measuring the magnitude of the main- sequence turn-off point relative to template Galactic globular clusters allows the relative ages of the clusters to be determined with a mean precision of 8.4 per cent, and down to 6 per cent for individual objects. We find that the mean age of our LMC cluster ensemble is identical to the mean age of the oldest metal-poor clusters in the Milky Way halo to 0.2 ± 0.4 Gyr. This provides the most sensitive test to date of the synchronicity of the earliest epoch of globular cluster formation in two independent galaxies. Horizontal branch magnitudes and subdwarf fitting to the main sequence allow us to determine distance estimates for each cluster and examine their geometric distribution in the LMC. Using two different methods, we find an average distance to the LMC of 18.52 ± 0.05.
How to tell an accreting boson star from a black hole h. olivares et al (2020)SOCIEDAD JULIO GARAVITO
Abstract
The tentative evidences for late time “echoes” in LIGO gravitational
waves (GWs) have been claimed to be signatures of horizonless compact
objects rather than vacuum black holes (BHs) possessing horizons. In
general, in the past, many authors have considered the possibility that
the so-called BHs might be only BH mimickers (BHMs). And recently
it has been suggested that the true astrophysical BH having no intrinsic
magnetic fields may be differentiated from magnetized BHMs by studying
the radial variations of magnetic fields around pertinent compact objects
(Lobanov, Nat. Astron. 2017). Here we highlight that close to the surface
of BHMs, the magnetic field pattern differs significantly from the same for
non-relativistic Neutron Stars (B ∼ r −3 ). In particular, we point out that
for ultra- compact BHMs, the polar field is weaker than the equatorial field
1by an extremely large factor of ∼ z s /lnz s , where z s ≫ 1 is the surface
gravitational redshift. We suggest that by studying the of radial variation
as well as such significant asymmetry of magnetic field structure near the
compact object, future observations may differentiate a theoretical black
hole from a astrophysical BH mimicker (a compact object). This study
also shows that even if some BHMs would be hypothesized to possess
magnetic fields even stronger than that of magnetars, in certain cases, they
may effectively behave as atoll type neutron stars possessing extremely low
magnetic fields.
Keywords: X-ray Binaries; Active Galactic Nuclei; Magnetic Field;
Black Hole Mimickers; Relativistic Astrophysics.
PACS numbers: 04.40.Dg, 97.80.Jp, 97.60.Gb, 95.86.Nv.
UV and Hα HST observations of 6 GASP jellyfish galaxiesSérgio Sacani
Star-forming, Hα-emitting clumps are found embedded in the gaseous tails of galaxies undergoing
intense ram pressure stripping in galaxy clusters, so-called jellyfish galaxies. These clumps offer a
unique opportunity to study star formation under extreme conditions, in the absence of an underlying
disk and embedded within the hot intracluster medium. Yet, a comprehensive, high spatial resolution
study of these systems is missing. We obtained UVIS/HST data to observe the first statistical sample
of clumps in the tails and disks of six jellyfish galaxies from the GASP survey; we used a combination
of broad-band (UV to I) filters and a narrow-band Hα filter. HST observations are needed to study
the sizes, stellar masses and ages of the clumps and their clustering hierarchy. These observations will
be used to study the clump scaling relations, the universality of the star formation process and verify
whether a disk is irrelevant, as hinted by jellyfish galaxy results. This paper presents the observations,
data reduction strategy, and some general results based on the preliminary data analysis. The UVIS
high spatial resolution gives an unprecedented sharp view of the complex structure of the inner regions
of the galaxies and of the substructures in the galaxy disks. We found clear signatures of stripping
in regions very close in projection to the galactic disk. The star-forming regions in the stripped tails
are extremely bright and compact while we did not detect a significant number of star-forming clumps
outside those detected by MUSE. The paper finally presents the development plan for the project.
UV and Hα HST observations of 6 GASP jellyfish galaxiesSérgio Sacani
Star-forming, Hα-emitting clumps are found embedded in the gaseous tails of galaxies undergoing
intense ram pressure stripping in galaxy clusters, so-called jellyfish galaxies. These clumps offer a
unique opportunity to study star formation under extreme conditions, in the absence of an underlying
disk and embedded within the hot intracluster medium. Yet, a comprehensive, high spatial resolution
study of these systems is missing. We obtained UVIS/HST data to observe the first statistical sample
of clumps in the tails and disks of six jellyfish galaxies from the GASP survey; we used a combination
of broad-band (UV to I) filters and a narrow-band Hα filter. HST observations are needed to study
the sizes, stellar masses and ages of the clumps and their clustering hierarchy. These observations will
be used to study the clump scaling relations, the universality of the star formation process and verify
whether a disk is irrelevant, as hinted by jellyfish galaxy results. This paper presents the observations,
data reduction strategy, and some general results based on the preliminary data analysis. The UVIS
high spatial resolution gives an unprecedented sharp view of the complex structure of the inner regions
of the galaxies and of the substructures in the galaxy disks. We found clear signatures of stripping
in regions very close in projection to the galactic disk. The star-forming regions in the stripped tails
are extremely bright and compact while we did not detect a significant number of star-forming clumps
outside those detected by MUSE. The paper finally presents the development plan for the project.
UV and Hα HST observations of 6 GASP jellyfish galaxiesSérgio Sacani
Star-forming, Hα-emitting clumps are found embedded in the gaseous tails of galaxies undergoing
intense ram pressure stripping in galaxy clusters, so-called jellyfish galaxies. These clumps offer a
unique opportunity to study star formation under extreme conditions, in the absence of an underlying
disk and embedded within the hot intracluster medium. Yet, a comprehensive, high spatial resolution
study of these systems is missing. We obtained UVIS/HST data to observe the first statistical sample
of clumps in the tails and disks of six jellyfish galaxies from the GASP survey; we used a combination
of broad-band (UV to I) filters and a narrow-band Hα filter. HST observations are needed to study
the sizes, stellar masses and ages of the clumps and their clustering hierarchy. These observations will
be used to study the clump scaling relations, the universality of the star formation process and verify
whether a disk is irrelevant, as hinted by jellyfish galaxy results. This paper presents the observations,
data reduction strategy, and some general results based on the preliminary data analysis. The UVIS
high spatial resolution gives an unprecedented sharp view of the complex structure of the inner regions
of the galaxies and of the substructures in the galaxy disks. We found clear signatures of stripping
in regions very close in projection to the galactic disk. The star-forming regions in the stripped tails
are extremely bright and compact while we did not detect a significant number of star-forming clumps
outside those detected by MUSE. The paper finally presents the development plan for the project.
An excess of massive stars in the local 30 Doradus starburstSérgio Sacani
The 30 Doradus star-forming region in the Large Magellanic Cloud is a nearby analog of large
star-formation events in the distant universe.We determined the recent formation history and
the initial mass function (IMF) of massive stars in 30 Doradus on the basis of spectroscopic
observations of 247 stars more massive than 15 solarmasses (M⊙).Themain episode of massive
star formation began about 8 million years (My) ago, and the star-formation rate seems to
have declined in the last 1 My.The IMF is densely sampled up to 200M⊙ and contains 32 ± 12%
more stars above 30 M⊙ than predicted by a standard Salpeter IMF. In the mass range of 15
to 200M⊙, the IMF power-law exponent is 1:90þ0:37
0:26, shallower than the Salpeter value of 2.35.
Spirals and clumps in V960 Mon: signs of planet formation via gravitational i...Sérgio Sacani
The formation of giant planets has traditionally been divided into two pathways: core accretion and gravitational instability. However, in recent years, gravitational instability has become less favored, primarily due
to the scarcity of observations of fragmented protoplanetary disks around young stars and low occurrence rate
of massive planets on very wide orbits. In this study, we present a SPHERE/IRDIS polarized light observation
of the young outbursting object V960 Mon. The image reveals a vast structure of intricately shaped scattered
light with several spiral arms. This finding motivated a re-analysis of archival ALMA 1.3 mm data acquired
just two years after the onset of the outburst of V960 Mon. In these data, we discover several clumps of continuum emission aligned along a spiral arm that coincides with the scattered light structure. We interpret the
localized emission as fragments formed from a spiral arm under gravitational collapse. Estimating the mass of
solids within these clumps to be of several Earth masses, we suggest this observation to be the first evidence of
gravitational instability occurring on planetary scales. This study discusses the significance of this finding for
planet formation and its potential connection with the outbursting state of V960 Mon.
This document presents color-magnitude diagrams derived from Hubble Space Telescope photometry of 6 outer Galactic globular clusters: Pyxis, Ruprecht 106, IC 4499, NGC 6426, NGC 7006, and Palomar 15. The deep photometry allows the ages of the clusters to be estimated from the main sequence turnoff. Preliminary age analysis reveals that IC 4499, Ruprecht 106, and Pyxis appear 1-2 billion years younger than inner halo clusters of similar metallicity, while NGC 7006 and Palomar 5 are marginally younger. NGC 6426 and Palomar 15, the two most metal-poor clusters, appear coeval with other metal-poor clusters within
SO and SiS Emission Tracing an Embedded Planet and Compact 12CO and 13CO Coun...Sérgio Sacani
Planets form in dusty, gas-rich disks around young stars, while at the same time, the planet formation
process alters the physical and chemical structure of the disk itself. Embedded planets will locally heat
the disk and sublimate volatile-rich ices, or in extreme cases, result in shocks that sputter heavy atoms
such as Si from dust grains. This should cause chemical asymmetries detectable in molecular gas
observations. Using high-angular-resolution ALMA archival data of the HD 169142 disk, we identify
compact SO J=88–77 and SiS J=19–18 emission coincident with the position of a ∼2 MJup planet seen
as a localized, Keplerian NIR feature within a gas-depleted, annular dust gap at ≈38 au. The SiS
emission is located along an azimuthal arc and has a similar morphology as a known 12CO kinematic
excess. This is the first tentative detection of SiS emission in a protoplanetary disk and suggests that
the planet is driving sufficiently strong shocks to produce gas-phase SiS. We also report the discovery of
compact 12CO and 13CO J=3–2 emission coincident with the planet location. Taken together, a planetdriven outflow provides the best explanation for the properties of the observed chemical asymmetries.
We also resolve a bright, azimuthally-asymmetric SO ring at ≈24 au. While most of this SO emission
originates from ice sublimation, its asymmetric distribution implies azimuthal temperature variations
driven by a misaligned inner disk or planet-disk interactions. Overall, the HD 169142 disk shows
several distinct chemical signatures related to giant planet formation and presents a powerful template
for future searches of planet-related chemical asymmetries in protoplanetary disks.
Asymmetry in the atmosphere of the ultra-hot Jupiter WASP-76 bSérgio Sacani
Context. WASP-76 b has been a recurrent subject of study since the detection of a signature in high-resolution transit spectroscopy
data indicating an asymmetry between the two limbs of the planet. The existence of this asymmetric signature has been confirmed by
multiple studies, but its physical origin is still under debate. In addition, it contrasts with the absence of asymmetry reported in the
infrared (IR) phase curve.
Aims. We provide a more comprehensive dataset of WASP-76 b with the goal of drawing a complete view of the physical processes
at work in this atmosphere. In particular, we attempt to reconcile visible high-resolution transit spectroscopy data and IR broadband
phase curves.
Methods. We gathered 3 phase curves, 20 occultations, and 6 transits for WASP-76 b in the visible with the CHEOPS space telescope.
We also report the analysis of three unpublished sectors observed by the TESS space telescope (also in the visible), which represents
34 phase curves.
Results. WASP-76 b displays an occultation of 260±11 and 152±10 ppm in TESS and CHEOPS bandpasses respectively. Depending
on the composition assumed for the atmosphere and the data reduction used for the IR data, we derived geometric albedo estimates
that range from 0.05 ± 0.023 to 0.146 ± 0.013 and from <0.13 to 0.189 ± 0.017 in the CHEOPS and TESS bandpasses, respectively. As
expected from the IR phase curves, a low-order model of the phase curves does not yield any detectable asymmetry in the visible either.
However, an empirical model allowing for sharper phase curve variations offers a hint of a flux excess before the occultation, with an
amplitude of ∼40 ppm, an orbital offset of ∼−30◦
, and a width of ∼20◦
. We also constrained the orbital eccentricity of WASP-76 b to
a value lower than 0.0067, with a 99.7% confidence level. This result contradicts earlier proposed scenarios aimed at explaining the
asymmetry observed in high-resolution transit spectroscopy.
Conclusions. In light of these findings, we hypothesise that WASP-76 b could have night-side clouds that extend predominantly
towards its eastern limb. At this limb, the clouds would be associated with spherical droplets or spherically shaped aerosols of an
unknown species, which would be responsible for a glory effect in the visible phase curves.
XUE: Molecular Inventory in the Inner Region of an Extremely Irradiated Proto...Sérgio Sacani
This document presents the first results from the JWST XUE program, which observed 15 protoplanetary disks in the NGC 6357 star-forming region using MIRI. For the disk XUE 1, located near massive stars, the following was found:
1) Abundant water, CO, CO2, HCN, and C2H2 were detected in the inner few AU, indicating an oxygen-dominated gas-phase chemistry similar to isolated disks.
2) Small crystalline silicate dust is present at the disk surface.
3) The column densities and chemistry are surprisingly similar to isolated disks despite the extreme radiation environment, implying inner disks can retain conditions conducive to rocky planet
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.
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”.
The Surprising Evolution of the Shadow on the TW Hya DiskSérgio Sacani
We report new total-intensity visible-light high-contrast imaging of the TW Hya disk taken with the Space
Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope. This represents the first published
images of the disk with STIS since 2016, when a moving shadow on the disk surface was reported. We continue
to see the shadow moving in a counterclockwise fashion, but in these new images the shadow has evolved into
two separate shadows, implying a change in behavior for the occulting structure. Based on radiative-transfer
models of optically thick disk structures casting shadows, we infer that a plausible explanation for the change is
that there are now two misaligned components of the inner disk. The first of these disks is located between 5 and
6 au with an inclination of 5.5° and position angle (PA) of 170°, and the second between 6 and 7 au with
an inclination of 7° and PA of 50°. Finally, we speculate on the implications of the new shadow structure
and determine that additional observations are needed to disentangle the nature of TW Hya’s inner-disk
architecture.
The Sparkler: Evolved High-redshift Globular Cluster Candidates Captured by JWSTSérgio Sacani
This document discusses compact red sources detected around a strongly lensed galaxy ("the Sparkler") at a redshift of 1.378 using JWST data. Photometry and morphological fits of the sources suggest they are spatially unresolved, very red, and consistent with old stellar populations. Spectroscopy shows emission from the galaxy but no signs of star formation in the red sources. The sources are most likely evolved globular clusters dating back to formation redshifts between 7-11, corresponding to ages of 3.9-4.1 billion years at the time of observation. If confirmed, these would be the first observed globular clusters at high redshift, opening a window into early globular cluster formation in the first billion years of
TOI-4600 b and c: Two Long-period Giant Planets Orbiting an Early K DwarfSérgio Sacani
We report the discovery and validation of two long-period giant exoplanets orbiting the early K dwarf TOI-4600
(V = 12.6, T = 11.9), first detected using observations from the Transiting Exoplanet Survey Satellite (TESS) by
the TESS Single Transit Planet Candidate Working Group. The inner planet, TOI-4600 b, has a radius of
6.80 ± 0.31 R⊕ and an orbital period of 82.69 days. The outer planet, TOI-4600 c, has a radius of 9.42 ± 0.42 R⊕
and an orbital period of 482.82 days, making it the longest-period confirmed or validated planet discovered by
TESS to date. We combine TESS photometry and ground-based spectroscopy, photometry, and high-resolution
imaging to validate the two planets. With equilibrium temperatures of 347 K and 191 K, respectively, TOI-4600 b
and c add to the small but growing population of temperate giant exoplanets that bridge the gap between hot/warm
Jupiters and the solar system’s gas giants. TOI-4600 is a promising target for further transit and precise RV
observations to measure the masses and orbits of the planets as well as search for additional nontransiting planets.
Additionally, with Transit Spectroscopy Metric values of ∼30, both planets are amenable for atmospheric
characterization with JWST. Together, these will lend insight into the formation and evolution of planet systems
with multiple giant exoplanets.
Stellar-mass black holes in the Hyades star cluster?Sérgio Sacani
Astrophysical models of binary-black hole mergers in the Universe require a significant fraction of stellar-mass black holes (BHs)
to receive negligible natal kicks to explain the gravitational wave detections. This implies that BHs should be retained even in
open clusters with low escape velocities (≲ 1 km/s). We search for signatures of the presence of BHs in the nearest open cluster
to the Sun – the Hyades – by comparing density profiles of direct 𝑁-body models to data from Gaia. The observations are best
reproduced by models with 2−3 BHs at present. Models that never possessed BHs have an half-mass radius ∼ 30% smaller than
the observed value, while those where the last BHs were ejected recently (≲ 150 Myr ago) can still reproduce the density profile.
In 50% of the models hosting BHs, we find BHs with stellar companion(s). Their period distribution peaks at ∼ 103 yr, making
them unlikely to be found through velocity variations. We look for potential BH companions through large Gaia astrometric and
spectroscopic errors, identifying 56 binary candidates - none of which consistent with a massive compact companion. Models
with 2 − 3 BHs have an elevated central velocity dispersion, but observations can not yet discriminate. We conclude that the
present-day structure of the Hyades requires a significant fraction of BHs to receive natal kicks smaller than the escape velocity
of ∼ 3 km s−1
at the time of BH formation and that the nearest BHs to the Sun are in, or near, Hyades.
Jet reorientation in central galaxies of clusters and groups: insights from V...Sérgio Sacani
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.
Reionization and the ISM/Stellar Origins with JWST and ALMA (RIOJA): The Core...Sérgio Sacani
The protoclusters in the epoch of reionization, traced by galaxy overdensity regions, are ideal laboratories for
studying the process of stellar assembly and cosmic reionization. We present the spectroscopic confirmation of the
core of the most distant protocluster at z = 7.88, A2744-z7p9OD, with the James Webb Space Telescope NIRSpec
integral field unit spectroscopy. The core region includes as many as four galaxies detected in [O III] 4960 and
5008 Å in a small area of ∼3″ × 3″, corresponding to ∼11 × 11 kpc, after the lensing magnification correction.
Three member galaxies are also tentatively detected in dust continuum in Atacama Large Millimeter/submillimeter
Array Band 6, which is consistent with their red ultraviolet continuum slopes, β ∼ −1.3. The member galaxies
have stellar masses in the range of log(M*/Me) ∼7.6–9.2 and star formation rates of ∼3–50 Me yr−1
, showing a
diversity in their properties. FirstLight cosmological simulations reproduce the physical properties of the member
galaxies including the stellar mass, [O III] luminosity, and dust-to-stellar mass ratio, and predict that the member
galaxies are on the verge of merging in a few to several tens of Myr to become a large galaxy with
M* ∼ 6 × 109
Me. The presence of a multiple merger and evolved galaxies in the core region of A2744-z7p9OD
indicates that environmental effects are already at work 650 Myr after the Big Bang.
Asymmetrical tidal tails of open star clusters: stars crossing their cluster’...Sérgio Sacani
The document discusses asymmetrical tidal tails observed around five open star clusters, which challenges Newtonian gravity. It summarizes how tidal tails form as stars escape clusters due to energy equipartition. Observations of the Hyades, Praesepe, Coma Berenices, COIN-Gaia 13, and NGC 752 clusters found more stars in the leading tidal tails within 50 pc of the clusters. Simulations show that in Newtonian gravity, tidal tails should be symmetrical, but asymmetries can arise in Milgromian dynamics. Future work is needed to better map tidal tails and develop Milgromian simulations.
Compositions of iron-meteorite parent bodies constrainthe structure of the pr...Sérgio Sacani
Magmatic iron-meteorite parent bodies are the earliest planetesimals in the Solar System,and they preserve information about conditions and planet-forming processes in thesolar nebula. In this study, we include comprehensive elemental compositions andfractional-crystallization modeling for iron meteorites from the cores of five differenti-ated asteroids from the inner Solar System. Together with previous results of metalliccores from the outer Solar System, we conclude that asteroidal cores from the outerSolar System have smaller sizes, elevated siderophile-element abundances, and simplercrystallization processes than those from the inner Solar System. These differences arerelated to the formation locations of the parent asteroids because the solar protoplane-tary disk varied in redox conditions, elemental distributions, and dynamics at differentheliocentric distances. Using highly siderophile-element data from iron meteorites, wereconstruct the distribution of calcium-aluminum-rich inclusions (CAIs) across theprotoplanetary disk within the first million years of Solar-System history. CAIs, the firstsolids to condense in the Solar System, formed close to the Sun. They were, however,concentrated within the outer disk and depleted within the inner disk. Future modelsof the structure and evolution of the protoplanetary disk should account for this dis-tribution pattern of CAIs.
Signatures of wave erosion in Titan’s coastsSérgio Sacani
The shorelines of Titan’s hydrocarbon seas trace flooded erosional landforms such as river valleys; however, it isunclear whether coastal erosion has subsequently altered these shorelines. Spacecraft observations and theo-retical models suggest that wind may cause waves to form on Titan’s seas, potentially driving coastal erosion,but the observational evidence of waves is indirect, and the processes affecting shoreline evolution on Titanremain unknown. No widely accepted framework exists for using shoreline morphology to quantitatively dis-cern coastal erosion mechanisms, even on Earth, where the dominant mechanisms are known. We combinelandscape evolution models with measurements of shoreline shape on Earth to characterize how differentcoastal erosion mechanisms affect shoreline morphology. Applying this framework to Titan, we find that theshorelines of Titan’s seas are most consistent with flooded landscapes that subsequently have been eroded bywaves, rather than a uniform erosional process or no coastal erosion, particularly if wave growth saturates atfetch lengths of tens of kilometers.
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UV and Hα HST observations of 6 GASP jellyfish galaxiesSérgio Sacani
Star-forming, Hα-emitting clumps are found embedded in the gaseous tails of galaxies undergoing
intense ram pressure stripping in galaxy clusters, so-called jellyfish galaxies. These clumps offer a
unique opportunity to study star formation under extreme conditions, in the absence of an underlying
disk and embedded within the hot intracluster medium. Yet, a comprehensive, high spatial resolution
study of these systems is missing. We obtained UVIS/HST data to observe the first statistical sample
of clumps in the tails and disks of six jellyfish galaxies from the GASP survey; we used a combination
of broad-band (UV to I) filters and a narrow-band Hα filter. HST observations are needed to study
the sizes, stellar masses and ages of the clumps and their clustering hierarchy. These observations will
be used to study the clump scaling relations, the universality of the star formation process and verify
whether a disk is irrelevant, as hinted by jellyfish galaxy results. This paper presents the observations,
data reduction strategy, and some general results based on the preliminary data analysis. The UVIS
high spatial resolution gives an unprecedented sharp view of the complex structure of the inner regions
of the galaxies and of the substructures in the galaxy disks. We found clear signatures of stripping
in regions very close in projection to the galactic disk. The star-forming regions in the stripped tails
are extremely bright and compact while we did not detect a significant number of star-forming clumps
outside those detected by MUSE. The paper finally presents the development plan for the project.
UV and Hα HST observations of 6 GASP jellyfish galaxiesSérgio Sacani
Star-forming, Hα-emitting clumps are found embedded in the gaseous tails of galaxies undergoing
intense ram pressure stripping in galaxy clusters, so-called jellyfish galaxies. These clumps offer a
unique opportunity to study star formation under extreme conditions, in the absence of an underlying
disk and embedded within the hot intracluster medium. Yet, a comprehensive, high spatial resolution
study of these systems is missing. We obtained UVIS/HST data to observe the first statistical sample
of clumps in the tails and disks of six jellyfish galaxies from the GASP survey; we used a combination
of broad-band (UV to I) filters and a narrow-band Hα filter. HST observations are needed to study
the sizes, stellar masses and ages of the clumps and their clustering hierarchy. These observations will
be used to study the clump scaling relations, the universality of the star formation process and verify
whether a disk is irrelevant, as hinted by jellyfish galaxy results. This paper presents the observations,
data reduction strategy, and some general results based on the preliminary data analysis. The UVIS
high spatial resolution gives an unprecedented sharp view of the complex structure of the inner regions
of the galaxies and of the substructures in the galaxy disks. We found clear signatures of stripping
in regions very close in projection to the galactic disk. The star-forming regions in the stripped tails
are extremely bright and compact while we did not detect a significant number of star-forming clumps
outside those detected by MUSE. The paper finally presents the development plan for the project.
UV and Hα HST observations of 6 GASP jellyfish galaxiesSérgio Sacani
Star-forming, Hα-emitting clumps are found embedded in the gaseous tails of galaxies undergoing
intense ram pressure stripping in galaxy clusters, so-called jellyfish galaxies. These clumps offer a
unique opportunity to study star formation under extreme conditions, in the absence of an underlying
disk and embedded within the hot intracluster medium. Yet, a comprehensive, high spatial resolution
study of these systems is missing. We obtained UVIS/HST data to observe the first statistical sample
of clumps in the tails and disks of six jellyfish galaxies from the GASP survey; we used a combination
of broad-band (UV to I) filters and a narrow-band Hα filter. HST observations are needed to study
the sizes, stellar masses and ages of the clumps and their clustering hierarchy. These observations will
be used to study the clump scaling relations, the universality of the star formation process and verify
whether a disk is irrelevant, as hinted by jellyfish galaxy results. This paper presents the observations,
data reduction strategy, and some general results based on the preliminary data analysis. The UVIS
high spatial resolution gives an unprecedented sharp view of the complex structure of the inner regions
of the galaxies and of the substructures in the galaxy disks. We found clear signatures of stripping
in regions very close in projection to the galactic disk. The star-forming regions in the stripped tails
are extremely bright and compact while we did not detect a significant number of star-forming clumps
outside those detected by MUSE. The paper finally presents the development plan for the project.
An excess of massive stars in the local 30 Doradus starburstSérgio Sacani
The 30 Doradus star-forming region in the Large Magellanic Cloud is a nearby analog of large
star-formation events in the distant universe.We determined the recent formation history and
the initial mass function (IMF) of massive stars in 30 Doradus on the basis of spectroscopic
observations of 247 stars more massive than 15 solarmasses (M⊙).Themain episode of massive
star formation began about 8 million years (My) ago, and the star-formation rate seems to
have declined in the last 1 My.The IMF is densely sampled up to 200M⊙ and contains 32 ± 12%
more stars above 30 M⊙ than predicted by a standard Salpeter IMF. In the mass range of 15
to 200M⊙, the IMF power-law exponent is 1:90þ0:37
0:26, shallower than the Salpeter value of 2.35.
Spirals and clumps in V960 Mon: signs of planet formation via gravitational i...Sérgio Sacani
The formation of giant planets has traditionally been divided into two pathways: core accretion and gravitational instability. However, in recent years, gravitational instability has become less favored, primarily due
to the scarcity of observations of fragmented protoplanetary disks around young stars and low occurrence rate
of massive planets on very wide orbits. In this study, we present a SPHERE/IRDIS polarized light observation
of the young outbursting object V960 Mon. The image reveals a vast structure of intricately shaped scattered
light with several spiral arms. This finding motivated a re-analysis of archival ALMA 1.3 mm data acquired
just two years after the onset of the outburst of V960 Mon. In these data, we discover several clumps of continuum emission aligned along a spiral arm that coincides with the scattered light structure. We interpret the
localized emission as fragments formed from a spiral arm under gravitational collapse. Estimating the mass of
solids within these clumps to be of several Earth masses, we suggest this observation to be the first evidence of
gravitational instability occurring on planetary scales. This study discusses the significance of this finding for
planet formation and its potential connection with the outbursting state of V960 Mon.
This document presents color-magnitude diagrams derived from Hubble Space Telescope photometry of 6 outer Galactic globular clusters: Pyxis, Ruprecht 106, IC 4499, NGC 6426, NGC 7006, and Palomar 15. The deep photometry allows the ages of the clusters to be estimated from the main sequence turnoff. Preliminary age analysis reveals that IC 4499, Ruprecht 106, and Pyxis appear 1-2 billion years younger than inner halo clusters of similar metallicity, while NGC 7006 and Palomar 5 are marginally younger. NGC 6426 and Palomar 15, the two most metal-poor clusters, appear coeval with other metal-poor clusters within
SO and SiS Emission Tracing an Embedded Planet and Compact 12CO and 13CO Coun...Sérgio Sacani
Planets form in dusty, gas-rich disks around young stars, while at the same time, the planet formation
process alters the physical and chemical structure of the disk itself. Embedded planets will locally heat
the disk and sublimate volatile-rich ices, or in extreme cases, result in shocks that sputter heavy atoms
such as Si from dust grains. This should cause chemical asymmetries detectable in molecular gas
observations. Using high-angular-resolution ALMA archival data of the HD 169142 disk, we identify
compact SO J=88–77 and SiS J=19–18 emission coincident with the position of a ∼2 MJup planet seen
as a localized, Keplerian NIR feature within a gas-depleted, annular dust gap at ≈38 au. The SiS
emission is located along an azimuthal arc and has a similar morphology as a known 12CO kinematic
excess. This is the first tentative detection of SiS emission in a protoplanetary disk and suggests that
the planet is driving sufficiently strong shocks to produce gas-phase SiS. We also report the discovery of
compact 12CO and 13CO J=3–2 emission coincident with the planet location. Taken together, a planetdriven outflow provides the best explanation for the properties of the observed chemical asymmetries.
We also resolve a bright, azimuthally-asymmetric SO ring at ≈24 au. While most of this SO emission
originates from ice sublimation, its asymmetric distribution implies azimuthal temperature variations
driven by a misaligned inner disk or planet-disk interactions. Overall, the HD 169142 disk shows
several distinct chemical signatures related to giant planet formation and presents a powerful template
for future searches of planet-related chemical asymmetries in protoplanetary disks.
Asymmetry in the atmosphere of the ultra-hot Jupiter WASP-76 bSérgio Sacani
Context. WASP-76 b has been a recurrent subject of study since the detection of a signature in high-resolution transit spectroscopy
data indicating an asymmetry between the two limbs of the planet. The existence of this asymmetric signature has been confirmed by
multiple studies, but its physical origin is still under debate. In addition, it contrasts with the absence of asymmetry reported in the
infrared (IR) phase curve.
Aims. We provide a more comprehensive dataset of WASP-76 b with the goal of drawing a complete view of the physical processes
at work in this atmosphere. In particular, we attempt to reconcile visible high-resolution transit spectroscopy data and IR broadband
phase curves.
Methods. We gathered 3 phase curves, 20 occultations, and 6 transits for WASP-76 b in the visible with the CHEOPS space telescope.
We also report the analysis of three unpublished sectors observed by the TESS space telescope (also in the visible), which represents
34 phase curves.
Results. WASP-76 b displays an occultation of 260±11 and 152±10 ppm in TESS and CHEOPS bandpasses respectively. Depending
on the composition assumed for the atmosphere and the data reduction used for the IR data, we derived geometric albedo estimates
that range from 0.05 ± 0.023 to 0.146 ± 0.013 and from <0.13 to 0.189 ± 0.017 in the CHEOPS and TESS bandpasses, respectively. As
expected from the IR phase curves, a low-order model of the phase curves does not yield any detectable asymmetry in the visible either.
However, an empirical model allowing for sharper phase curve variations offers a hint of a flux excess before the occultation, with an
amplitude of ∼40 ppm, an orbital offset of ∼−30◦
, and a width of ∼20◦
. We also constrained the orbital eccentricity of WASP-76 b to
a value lower than 0.0067, with a 99.7% confidence level. This result contradicts earlier proposed scenarios aimed at explaining the
asymmetry observed in high-resolution transit spectroscopy.
Conclusions. In light of these findings, we hypothesise that WASP-76 b could have night-side clouds that extend predominantly
towards its eastern limb. At this limb, the clouds would be associated with spherical droplets or spherically shaped aerosols of an
unknown species, which would be responsible for a glory effect in the visible phase curves.
XUE: Molecular Inventory in the Inner Region of an Extremely Irradiated Proto...Sérgio Sacani
This document presents the first results from the JWST XUE program, which observed 15 protoplanetary disks in the NGC 6357 star-forming region using MIRI. For the disk XUE 1, located near massive stars, the following was found:
1) Abundant water, CO, CO2, HCN, and C2H2 were detected in the inner few AU, indicating an oxygen-dominated gas-phase chemistry similar to isolated disks.
2) Small crystalline silicate dust is present at the disk surface.
3) The column densities and chemistry are surprisingly similar to isolated disks despite the extreme radiation environment, implying inner disks can retain conditions conducive to rocky planet
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.
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”.
The Surprising Evolution of the Shadow on the TW Hya DiskSérgio Sacani
We report new total-intensity visible-light high-contrast imaging of the TW Hya disk taken with the Space
Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope. This represents the first published
images of the disk with STIS since 2016, when a moving shadow on the disk surface was reported. We continue
to see the shadow moving in a counterclockwise fashion, but in these new images the shadow has evolved into
two separate shadows, implying a change in behavior for the occulting structure. Based on radiative-transfer
models of optically thick disk structures casting shadows, we infer that a plausible explanation for the change is
that there are now two misaligned components of the inner disk. The first of these disks is located between 5 and
6 au with an inclination of 5.5° and position angle (PA) of 170°, and the second between 6 and 7 au with
an inclination of 7° and PA of 50°. Finally, we speculate on the implications of the new shadow structure
and determine that additional observations are needed to disentangle the nature of TW Hya’s inner-disk
architecture.
The Sparkler: Evolved High-redshift Globular Cluster Candidates Captured by JWSTSérgio Sacani
This document discusses compact red sources detected around a strongly lensed galaxy ("the Sparkler") at a redshift of 1.378 using JWST data. Photometry and morphological fits of the sources suggest they are spatially unresolved, very red, and consistent with old stellar populations. Spectroscopy shows emission from the galaxy but no signs of star formation in the red sources. The sources are most likely evolved globular clusters dating back to formation redshifts between 7-11, corresponding to ages of 3.9-4.1 billion years at the time of observation. If confirmed, these would be the first observed globular clusters at high redshift, opening a window into early globular cluster formation in the first billion years of
TOI-4600 b and c: Two Long-period Giant Planets Orbiting an Early K DwarfSérgio Sacani
We report the discovery and validation of two long-period giant exoplanets orbiting the early K dwarf TOI-4600
(V = 12.6, T = 11.9), first detected using observations from the Transiting Exoplanet Survey Satellite (TESS) by
the TESS Single Transit Planet Candidate Working Group. The inner planet, TOI-4600 b, has a radius of
6.80 ± 0.31 R⊕ and an orbital period of 82.69 days. The outer planet, TOI-4600 c, has a radius of 9.42 ± 0.42 R⊕
and an orbital period of 482.82 days, making it the longest-period confirmed or validated planet discovered by
TESS to date. We combine TESS photometry and ground-based spectroscopy, photometry, and high-resolution
imaging to validate the two planets. With equilibrium temperatures of 347 K and 191 K, respectively, TOI-4600 b
and c add to the small but growing population of temperate giant exoplanets that bridge the gap between hot/warm
Jupiters and the solar system’s gas giants. TOI-4600 is a promising target for further transit and precise RV
observations to measure the masses and orbits of the planets as well as search for additional nontransiting planets.
Additionally, with Transit Spectroscopy Metric values of ∼30, both planets are amenable for atmospheric
characterization with JWST. Together, these will lend insight into the formation and evolution of planet systems
with multiple giant exoplanets.
Stellar-mass black holes in the Hyades star cluster?Sérgio Sacani
Astrophysical models of binary-black hole mergers in the Universe require a significant fraction of stellar-mass black holes (BHs)
to receive negligible natal kicks to explain the gravitational wave detections. This implies that BHs should be retained even in
open clusters with low escape velocities (≲ 1 km/s). We search for signatures of the presence of BHs in the nearest open cluster
to the Sun – the Hyades – by comparing density profiles of direct 𝑁-body models to data from Gaia. The observations are best
reproduced by models with 2−3 BHs at present. Models that never possessed BHs have an half-mass radius ∼ 30% smaller than
the observed value, while those where the last BHs were ejected recently (≲ 150 Myr ago) can still reproduce the density profile.
In 50% of the models hosting BHs, we find BHs with stellar companion(s). Their period distribution peaks at ∼ 103 yr, making
them unlikely to be found through velocity variations. We look for potential BH companions through large Gaia astrometric and
spectroscopic errors, identifying 56 binary candidates - none of which consistent with a massive compact companion. Models
with 2 − 3 BHs have an elevated central velocity dispersion, but observations can not yet discriminate. We conclude that the
present-day structure of the Hyades requires a significant fraction of BHs to receive natal kicks smaller than the escape velocity
of ∼ 3 km s−1
at the time of BH formation and that the nearest BHs to the Sun are in, or near, Hyades.
Jet reorientation in central galaxies of clusters and groups: insights from V...Sérgio Sacani
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.
Reionization and the ISM/Stellar Origins with JWST and ALMA (RIOJA): The Core...Sérgio Sacani
The protoclusters in the epoch of reionization, traced by galaxy overdensity regions, are ideal laboratories for
studying the process of stellar assembly and cosmic reionization. We present the spectroscopic confirmation of the
core of the most distant protocluster at z = 7.88, A2744-z7p9OD, with the James Webb Space Telescope NIRSpec
integral field unit spectroscopy. The core region includes as many as four galaxies detected in [O III] 4960 and
5008 Å in a small area of ∼3″ × 3″, corresponding to ∼11 × 11 kpc, after the lensing magnification correction.
Three member galaxies are also tentatively detected in dust continuum in Atacama Large Millimeter/submillimeter
Array Band 6, which is consistent with their red ultraviolet continuum slopes, β ∼ −1.3. The member galaxies
have stellar masses in the range of log(M*/Me) ∼7.6–9.2 and star formation rates of ∼3–50 Me yr−1
, showing a
diversity in their properties. FirstLight cosmological simulations reproduce the physical properties of the member
galaxies including the stellar mass, [O III] luminosity, and dust-to-stellar mass ratio, and predict that the member
galaxies are on the verge of merging in a few to several tens of Myr to become a large galaxy with
M* ∼ 6 × 109
Me. The presence of a multiple merger and evolved galaxies in the core region of A2744-z7p9OD
indicates that environmental effects are already at work 650 Myr after the Big Bang.
Asymmetrical tidal tails of open star clusters: stars crossing their cluster’...Sérgio Sacani
The document discusses asymmetrical tidal tails observed around five open star clusters, which challenges Newtonian gravity. It summarizes how tidal tails form as stars escape clusters due to energy equipartition. Observations of the Hyades, Praesepe, Coma Berenices, COIN-Gaia 13, and NGC 752 clusters found more stars in the leading tidal tails within 50 pc of the clusters. Simulations show that in Newtonian gravity, tidal tails should be symmetrical, but asymmetries can arise in Milgromian dynamics. Future work is needed to better map tidal tails and develop Milgromian simulations.
Similar to Collimation of the Relativistic Jet in the Quasar 3C273 (20)
Compositions of iron-meteorite parent bodies constrainthe structure of the pr...Sérgio Sacani
Magmatic iron-meteorite parent bodies are the earliest planetesimals in the Solar System,and they preserve information about conditions and planet-forming processes in thesolar nebula. In this study, we include comprehensive elemental compositions andfractional-crystallization modeling for iron meteorites from the cores of five differenti-ated asteroids from the inner Solar System. Together with previous results of metalliccores from the outer Solar System, we conclude that asteroidal cores from the outerSolar System have smaller sizes, elevated siderophile-element abundances, and simplercrystallization processes than those from the inner Solar System. These differences arerelated to the formation locations of the parent asteroids because the solar protoplane-tary disk varied in redox conditions, elemental distributions, and dynamics at differentheliocentric distances. Using highly siderophile-element data from iron meteorites, wereconstruct the distribution of calcium-aluminum-rich inclusions (CAIs) across theprotoplanetary disk within the first million years of Solar-System history. CAIs, the firstsolids to condense in the Solar System, formed close to the Sun. They were, however,concentrated within the outer disk and depleted within the inner disk. Future modelsof the structure and evolution of the protoplanetary disk should account for this dis-tribution pattern of CAIs.
Signatures of wave erosion in Titan’s coastsSérgio Sacani
The shorelines of Titan’s hydrocarbon seas trace flooded erosional landforms such as river valleys; however, it isunclear whether coastal erosion has subsequently altered these shorelines. Spacecraft observations and theo-retical models suggest that wind may cause waves to form on Titan’s seas, potentially driving coastal erosion,but the observational evidence of waves is indirect, and the processes affecting shoreline evolution on Titanremain unknown. No widely accepted framework exists for using shoreline morphology to quantitatively dis-cern coastal erosion mechanisms, even on Earth, where the dominant mechanisms are known. We combinelandscape evolution models with measurements of shoreline shape on Earth to characterize how differentcoastal erosion mechanisms affect shoreline morphology. Applying this framework to Titan, we find that theshorelines of Titan’s seas are most consistent with flooded landscapes that subsequently have been eroded bywaves, rather than a uniform erosional process or no coastal erosion, particularly if wave growth saturates atfetch lengths of tens of kilometers.
SDSS1335+0728: The awakening of a ∼ 106M⊙ black hole⋆Sérgio Sacani
Context. The early-type galaxy SDSS J133519.91+072807.4 (hereafter SDSS1335+0728), which had exhibited no prior optical variations during the preceding two decades, began showing significant nuclear variability in the Zwicky Transient Facility (ZTF) alert stream from December 2019 (as ZTF19acnskyy). This variability behaviour, coupled with the host-galaxy properties, suggests that SDSS1335+0728 hosts a ∼ 106M⊙ black hole (BH) that is currently in the process of ‘turning on’. Aims. We present a multi-wavelength photometric analysis and spectroscopic follow-up performed with the aim of better understanding the origin of the nuclear variations detected in SDSS1335+0728. Methods. We used archival photometry (from WISE, 2MASS, SDSS, GALEX, eROSITA) and spectroscopic data (from SDSS and LAMOST) to study the state of SDSS1335+0728 prior to December 2019, and new observations from Swift, SOAR/Goodman, VLT/X-shooter, and Keck/LRIS taken after its turn-on to characterise its current state. We analysed the variability of SDSS1335+0728 in the X-ray/UV/optical/mid-infrared range, modelled its spectral energy distribution prior to and after December 2019, and studied the evolution of its UV/optical spectra. Results. From our multi-wavelength photometric analysis, we find that: (a) since 2021, the UV flux (from Swift/UVOT observations) is four times brighter than the flux reported by GALEX in 2004; (b) since June 2022, the mid-infrared flux has risen more than two times, and the W1−W2 WISE colour has become redder; and (c) since February 2024, the source has begun showing X-ray emission. From our spectroscopic follow-up, we see that (i) the narrow emission line ratios are now consistent with a more energetic ionising continuum; (ii) broad emission lines are not detected; and (iii) the [OIII] line increased its flux ∼ 3.6 years after the first ZTF alert, which implies a relatively compact narrow-line-emitting region. Conclusions. We conclude that the variations observed in SDSS1335+0728 could be either explained by a ∼ 106M⊙ AGN that is just turning on or by an exotic tidal disruption event (TDE). If the former is true, SDSS1335+0728 is one of the strongest cases of an AGNobserved in the process of activating. If the latter were found to be the case, it would correspond to the longest and faintest TDE ever observed (or another class of still unknown nuclear transient). Future observations of SDSS1335+0728 are crucial to further understand its behaviour. Key words. galaxies: active– accretion, accretion discs– galaxies: individual: SDSS J133519.91+072807.4
Discovery of An Apparent Red, High-Velocity Type Ia Supernova at 𝐳 = 2.9 wi...Sérgio Sacani
We present the JWST discovery of SN 2023adsy, a transient object located in a host galaxy JADES-GS
+
53.13485
−
27.82088
with a host spectroscopic redshift of
2.903
±
0.007
. The transient was identified in deep James Webb Space Telescope (JWST)/NIRCam imaging from the JWST Advanced Deep Extragalactic Survey (JADES) program. Photometric and spectroscopic followup with NIRCam and NIRSpec, respectively, confirm the redshift and yield UV-NIR light-curve, NIR color, and spectroscopic information all consistent with a Type Ia classification. Despite its classification as a likely SN Ia, SN 2023adsy is both fairly red (
�
(
�
−
�
)
∼
0.9
) despite a host galaxy with low-extinction and has a high Ca II velocity (
19
,
000
±
2
,
000
km/s) compared to the general population of SNe Ia. While these characteristics are consistent with some Ca-rich SNe Ia, particularly SN 2016hnk, SN 2023adsy is intrinsically brighter than the low-
�
Ca-rich population. Although such an object is too red for any low-
�
cosmological sample, we apply a fiducial standardization approach to SN 2023adsy and find that the SN 2023adsy luminosity distance measurement is in excellent agreement (
≲
1
�
) with
Λ
CDM. Therefore unlike low-
�
Ca-rich SNe Ia, SN 2023adsy is standardizable and gives no indication that SN Ia standardized luminosities change significantly with redshift. A larger sample of distant SNe Ia is required to determine if SN Ia population characteristics at high-
�
truly diverge from their low-
�
counterparts, and to confirm that standardized luminosities nevertheless remain constant with redshift.
Evidence of Jet Activity from the Secondary Black Hole in the OJ 287 Binary S...Sérgio Sacani
Wereport the study of a huge optical intraday flare on 2021 November 12 at 2 a.m. UT in the blazar OJ287. In the binary black hole model, it is associated with an impact of the secondary black hole on the accretion disk of the primary. Our multifrequency observing campaign was set up to search for such a signature of the impact based on a prediction made 8 yr earlier. The first I-band results of the flare have already been reported by Kishore et al. (2024). Here we combine these data with our monitoring in the R-band. There is a big change in the R–I spectral index by 1.0 ±0.1 between the normal background and the flare, suggesting a new component of radiation. The polarization variation during the rise of the flare suggests the same. The limits on the source size place it most reasonably in the jet of the secondary BH. We then ask why we have not seen this phenomenon before. We show that OJ287 was never before observed with sufficient sensitivity on the night when the flare should have happened according to the binary model. We also study the probability that this flare is just an oversized example of intraday variability using the Krakow data set of intense monitoring between 2015 and 2023. We find that the occurrence of a flare of this size and rapidity is unlikely. In machine-readable Tables 1 and 2, we give the full orbit-linked historical light curve of OJ287 as well as the dense monitoring sample of Krakow.
Candidate young stellar objects in the S-cluster: Kinematic analysis of a sub...Sérgio Sacani
Context. The observation of several L-band emission sources in the S cluster has led to a rich discussion of their nature. However, a definitive answer to the classification of the dusty objects requires an explanation for the detection of compact Doppler-shifted Brγ emission. The ionized hydrogen in combination with the observation of mid-infrared L-band continuum emission suggests that most of these sources are embedded in a dusty envelope. These embedded sources are part of the S-cluster, and their relationship to the S-stars is still under debate. To date, the question of the origin of these two populations has been vague, although all explanations favor migration processes for the individual cluster members. Aims. This work revisits the S-cluster and its dusty members orbiting the supermassive black hole SgrA* on bound Keplerian orbits from a kinematic perspective. The aim is to explore the Keplerian parameters for patterns that might imply a nonrandom distribution of the sample. Additionally, various analytical aspects are considered to address the nature of the dusty sources. Methods. Based on the photometric analysis, we estimated the individual H−K and K−L colors for the source sample and compared the results to known cluster members. The classification revealed a noticeable contrast between the S-stars and the dusty sources. To fit the flux-density distribution, we utilized the radiative transfer code HYPERION and implemented a young stellar object Class I model. We obtained the position angle from the Keplerian fit results; additionally, we analyzed the distribution of the inclinations and the longitudes of the ascending node. Results. The colors of the dusty sources suggest a stellar nature consistent with the spectral energy distribution in the near and midinfrared domains. Furthermore, the evaporation timescales of dusty and gaseous clumps in the vicinity of SgrA* are much shorter ( 2yr) than the epochs covered by the observations (≈15yr). In addition to the strong evidence for the stellar classification of the D-sources, we also find a clear disk-like pattern following the arrangements of S-stars proposed in the literature. Furthermore, we find a global intrinsic inclination for all dusty sources of 60 ± 20◦, implying a common formation process. Conclusions. The pattern of the dusty sources manifested in the distribution of the position angles, inclinations, and longitudes of the ascending node strongly suggests two different scenarios: the main-sequence stars and the dusty stellar S-cluster sources share a common formation history or migrated with a similar formation channel in the vicinity of SgrA*. Alternatively, the gravitational influence of SgrA* in combination with a massive perturber, such as a putative intermediate mass black hole in the IRS 13 cluster, forces the dusty objects and S-stars to follow a particular orbital arrangement. Key words. stars: black holes– stars: formation– Galaxy: center– galaxies: star formation
JAMES WEBB STUDY THE MASSIVE BLACK HOLE SEEDSSérgio Sacani
The pathway(s) to seeding the massive black holes (MBHs) that exist at the heart of galaxies in the present and distant Universe remains an unsolved problem. Here we categorise, describe and quantitatively discuss the formation pathways of both light and heavy seeds. We emphasise that the most recent computational models suggest that rather than a bimodal-like mass spectrum between light and heavy seeds with light at one end and heavy at the other that instead a continuum exists. Light seeds being more ubiquitous and the heavier seeds becoming less and less abundant due the rarer environmental conditions required for their formation. We therefore examine the different mechanisms that give rise to different seed mass spectrums. We show how and why the mechanisms that produce the heaviest seeds are also among the rarest events in the Universe and are hence extremely unlikely to be the seeds for the vast majority of the MBH population. We quantify, within the limits of the current large uncertainties in the seeding processes, the expected number densities of the seed mass spectrum. We argue that light seeds must be at least 103 to 105 times more numerous than heavy seeds to explain the MBH population as a whole. Based on our current understanding of the seed population this makes heavy seeds (Mseed > 103 M⊙) a significantly more likely pathway given that heavy seeds have an abundance pattern than is close to and likely in excess of 10−4 compared to light seeds. Finally, we examine the current state-of-the-art in numerical calculations and recent observations and plot a path forward for near-future advances in both domains.
Anti-Universe And Emergent Gravity and the Dark UniverseSérgio Sacani
Recent theoretical progress indicates that spacetime and gravity emerge together from the entanglement structure of an underlying microscopic theory. These ideas are best understood in Anti-de Sitter space, where they rely on the area law for entanglement entropy. The extension to de Sitter space requires taking into account the entropy and temperature associated with the cosmological horizon. Using insights from string theory, black hole physics and quantum information theory we argue that the positive dark energy leads to a thermal volume law contribution to the entropy that overtakes the area law precisely at the cosmological horizon. Due to the competition between area and volume law entanglement the microscopic de Sitter states do not thermalise at sub-Hubble scales: they exhibit memory effects in the form of an entropy displacement caused by matter. The emergent laws of gravity contain an additional ‘dark’ gravitational force describing the ‘elastic’ response due to the entropy displacement. We derive an estimate of the strength of this extra force in terms of the baryonic mass, Newton’s constant and the Hubble acceleration scale a0 = cH0, and provide evidence for the fact that this additional ‘dark gravity force’ explains the observed phenomena in galaxies and clusters currently attributed to dark matter.
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.
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.
Mechanisms and Applications of Antiviral Neutralizing Antibodies - Creative B...Creative-Biolabs
Neutralizing antibodies, pivotal in immune defense, specifically bind and inhibit viral pathogens, thereby playing a crucial role in protecting against and mitigating infectious diseases. In this slide, we will introduce what antibodies and neutralizing antibodies are, the production and regulation of neutralizing antibodies, their mechanisms of action, classification and applications, as well as the challenges they face.
Immersive Learning That Works: Research Grounding and Paths ForwardLeonel Morgado
We will metaverse into the essence of immersive learning, into its three dimensions and conceptual models. This approach encompasses elements from teaching methodologies to social involvement, through organizational concerns and technologies. Challenging the perception of learning as knowledge transfer, we introduce a 'Uses, Practices & Strategies' model operationalized by the 'Immersive Learning Brain' and ‘Immersion Cube’ frameworks. This approach offers a comprehensive guide through the intricacies of immersive educational experiences and spotlighting research frontiers, along the immersion dimensions of system, narrative, and agency. Our discourse extends to stakeholders beyond the academic sphere, addressing the interests of technologists, instructional designers, and policymakers. We span various contexts, from formal education to organizational transformation to the new horizon of an AI-pervasive society. This keynote aims to unite the iLRN community in a collaborative journey towards a future where immersive learning research and practice coalesce, paving the way for innovative educational research and practice landscapes.
PPT on Alternate Wetting and Drying 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.
_Extraction of Ethylene oxide and 2-Chloroethanol from alternate matrices Li...LucyHearn1
How do you know your food is safe?
Last Friday was world World Food Safety Day, facilitated by the Food and Agriculture Organization of the United Nations (FAO) and the World Health Organization (WHO) in which the slogan rightly says, 'food safety is everyone's business'. Due to this, I thought it would be worth sharing some data that I have worked on in this field!
Working at Markes International has really opened my eyes (and unfortunately my friends and family 🤣) to food safety and quality, especially with my recent application work on ethylene oxide and 2-chloroethanol residues in foodstuffs, as of the biggest global food recalls in history was and is still being implemented by the Rapid alert system for food and feed (RASFF) in 2021, for high levels of these carcinogenic compounds.
Travis Hills of MN is Making Clean Water Accessible to All Through High Flux ...Travis Hills MN
By harnessing the power of High Flux Vacuum Membrane Distillation, Travis Hills from MN envisions a future where clean and safe drinking water is accessible to all, regardless of geographical location or economic status.
(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.
Microbial interaction
Microorganisms interacts with each other and can be physically associated with another organisms in a variety of ways.
One organism can be located on the surface of another organism as an ectobiont or located within another organism as endobiont.
Microbial interaction may be positive such as mutualism, proto-cooperation, commensalism or may be negative such as parasitism, predation or competition
Types of microbial interaction
Positive interaction: mutualism, proto-cooperation, commensalism
Negative interaction: Ammensalism (antagonism), parasitism, predation, competition
I. Mutualism:
It is defined as the relationship in which each organism in interaction gets benefits from association. It is an obligatory relationship in which mutualist and host are metabolically dependent on each other.
Mutualistic relationship is very specific where one member of association cannot be replaced by another species.
Mutualism require close physical contact between interacting organisms.
Relationship of mutualism allows organisms to exist in habitat that could not occupied by either species alone.
Mutualistic relationship between organisms allows them to act as a single organism.
Examples of mutualism:
i. Lichens:
Lichens are excellent example of mutualism.
They are the association of specific fungi and certain genus of algae. In lichen, fungal partner is called mycobiont and algal partner is called
II. Syntrophism:
It is an association in which the growth of one organism either depends on or improved by the substrate provided by another organism.
In syntrophism both organism in association gets benefits.
Compound A
Utilized by population 1
Compound B
Utilized by population 2
Compound C
utilized by both Population 1+2
Products
In this theoretical example of syntrophism, population 1 is able to utilize and metabolize compound A, forming compound B but cannot metabolize beyond compound B without co-operation of population 2. Population 2is unable to utilize compound A but it can metabolize compound B forming compound C. Then both population 1 and 2 are able to carry out metabolic reaction which leads to formation of end product that neither population could produce alone.
Examples of syntrophism:
i. Methanogenic ecosystem in sludge digester
Methane produced by methanogenic bacteria depends upon interspecies hydrogen transfer by other fermentative bacteria.
Anaerobic fermentative bacteria generate CO2 and H2 utilizing carbohydrates which is then utilized by methanogenic bacteria (Methanobacter) to produce methane.
ii. Lactobacillus arobinosus and Enterococcus faecalis:
In the minimal media, Lactobacillus arobinosus and Enterococcus faecalis are able to grow together but not alone.
The synergistic relationship between E. faecalis and L. arobinosus occurs in which E. faecalis require folic acid
CLASS 12th CHEMISTRY SOLID STATE ppt (Animated)eitps1506
Description:
Dive into the fascinating realm of solid-state physics with our meticulously crafted online PowerPoint presentation. This immersive educational resource offers a comprehensive exploration of the fundamental concepts, theories, and applications within the realm of solid-state physics.
From crystalline structures to semiconductor devices, this presentation delves into the intricate principles governing the behavior of solids, providing clear explanations and illustrative examples to enhance understanding. Whether you're a student delving into the subject for the first time or a seasoned researcher seeking to deepen your knowledge, our presentation offers valuable insights and in-depth analyses to cater to various levels of expertise.
Key topics covered include:
Crystal Structures: Unravel the mysteries of crystalline arrangements and their significance in determining material properties.
Band Theory: Explore the electronic band structure of solids and understand how it influences their conductive properties.
Semiconductor Physics: Delve into the behavior of semiconductors, including doping, carrier transport, and device applications.
Magnetic Properties: Investigate the magnetic behavior of solids, including ferromagnetism, antiferromagnetism, and ferrimagnetism.
Optical Properties: Examine the interaction of light with solids, including absorption, reflection, and transmission phenomena.
With visually engaging slides, informative content, and interactive elements, our online PowerPoint presentation serves as a valuable resource for students, educators, and enthusiasts alike, facilitating a deeper understanding of the captivating world of solid-state physics. Explore the intricacies of solid-state materials and unlock the secrets behind their remarkable properties with our comprehensive presentation.
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.
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.
2. AGN jet physics (e.g., reviewed in Blandford et al. 2019). In
particular, jet collimation processes have been studied by
focusing on jet structures since they provide various informa-
tion not only about the jet itself but also about their surrounding
environment contributing to jet confinement (Begelman & Li
1994; Komissarov et al. 2007, 2009; Fromm et al. 2018).
The detailed nature of the jet collimation can be addressed by
high-angular-resolution observations using very long baseline
interferometry (VLBI; e.g., Boccardi et al. 2017; Hada 2019),
allowing direct comparisons with special or general relativistic
(SR or GR) magnetohydrodynamic simulations (Chael et al.
2018; Nakamura et al. 2018; Fromm et al. 2019). In particular,
intensive studies of the M87 jet in the last decade have pro-
vided new insights about jet collimation since that jet is the best
source for investigating the global jet structures from the
immediate vicinity of the central black hole (BH) to beyond the
host galaxy (Asada & Nakamura 2012; Hada et al. 2013, 2016;
Nakamura & Asada 2013; Kim et al. 2018; Walker et al. 2018;
Event Horizon Telescope Collaboration et al. 2019a; Park et al.
2019a). Following the aforementioned pioneering works on
M87, jet shapes have been measured mainly from several
nearby sources: NGC 6251 (Tseng et al. 2016), NGC 4261
(Nakahara et al. 2018), 1H 0323+342 (Hada et al. 2018),
Cygnus A (Boccardi et al. 2016; Nakahara et al. 2019),
NGC 1052 (Nakahara et al. 2020; Baczko et al. 2022),
NGC 315 (Boccardi et al. 2021; Park et al. 2021), 3C 84 (Nagai
et al. 2014; Giovannini et al. 2018), and for a large number of
jet samples collected by the long-term monitoring MOJAVE
program31
(Pushkarev et al. 2017). More recently, Kovalev
et al. (2020) investigated jet widths from over 300 sources and
found the transitions of jet shapes from 10 nearby sources.
They also found that the range of the transition locations is
∼105–6
gravitational radii from the core, which may indicate a
common property of nearby AGN jets.
The collimation properties of distant quasars are still unclear
due to the difficulties in resolving the transverse jet shape.
Indeed, Algaba et al. (2017) systematically measured core sizes
for distant radio-loud AGNs to investigate the upstream jet
structures. However, the core size is often unresolved even at an
extremely high angular resolution with a space radio dish (e.g.,
Gómez et al. 2016), and is often measured with high systematic
uncertainties resulting from the limited angular resolution.
Although the jet structure of the flat-spectrum radio quasar
(FSRQ) 4C 38.41 was measured by Algaba et al. (2019), they
could not detect significant collimation breaks because of the
limited range of the measured jet scales. In addition, the phy-
sical parameters for this source, such as the BH mass and the jet
viewing angle, have large uncertainties. Therefore, to under-
stand the jet collimation for high-powered AGN like quasars,
observations with a high angular resolution for the well-studied
sources at other wavelengths are required to transversely resolve
the detailed structures down to the bases of the jets.
In this paper, we study the quasar 3C 273 (1226+023), well
known as one of the brightest extragalactic objects and the
closest quasars (Schmidt 1963) with prominent jets (Davis et al.
1985; Conway et al. 1993; Bahcall et al. 1995; Jester et al. 2005;
Perley & Meisenheimer 2017). The 3C 273 jets have been
observed many times since their discovery because the elon-
gated jet is a unique target for resolving down to the central
(sub)parsec scale with VLBI observations (Krichbaum et al.
1990; Lobanov & Zensus 2001; Savolainen et al. 2006; Kovalev
et al. 2016; Bruni et al. 2017, 2021; Jorstad et al. 2017; Lister
et al. 2019, 2021). Furthermore, recent infrared interferometric
observations with the GRAVITY instrument on the Very Large
Telescope Interferometer (Gravity Collaboration et al. 2017)
precisely estimated the BH mass and viewing angle for 3C 273
as MBH = (2.6 ± 1.1) × 108
Me and θ = 12° ± 2° (Gravity
Collaboration et al. 2018).32
The estimated BH mass yields a
linear angular relation of 1 mas ∼ 2.7 pc ∼ 1.2 × 105
Rs, which
makes 3C 273 one of the best-resolved quasars. For these
reasons, 3C 273 is the ideal target for investigating the global
structure of a quasar jet. For 3C 273, a preliminary detection of
the transition from the parabolic to conical shape has been
reported in an early work of a subset of the authors in a con-
ference proceeding (Akiyama et al. 2018), based on a marginal
detection of a parabolic jet from single-band data sets at
43 GHz only covering a narrow range of the spatial area. It also
lacks a careful consideration of frequency-dependent locations
of radio cores at different frequencies due to the effect of
synchrotron self-absorption relevant for the innermost jet pro-
bed at millimeter wavelengths. The presence of the transition
has remained inconclusive in the earlier work.
In this paper, we report new multifrequency observations of
the jet of the quasar 3C 273 observed with several global VLBI
networks. In particular, the Global Millimeter VLBI Array
(GMVA) at 3.5 mm/86 GHz including the phased Atacama
Large Millimeter/submillimeter Array (ALMA; Matthews
et al. 2018) provided a strong advantage, remarkably increasing
the north–south resolution and sensitivity (see also Issaoun
et al. 2019 for the first published image with GMVA+ALMA
on Sgr A*
). These observations provided us with high-fidelity
imaging of the finest jet structure of 3C 273 from the innermost
subparsec scale region with a maximum resolution of several
tens of microarcseconds (μas).
The paper is organized as follows. In Section 2, we describe
the observations and data reduction. Images were reconstructed
with the state-of-the-art regularized maximum likelihood meth-
ods as described in Section 3, and further analyzed in Section 4.
We show the global jet structure of 3C 273, including the core
shift measurements and the jet collimation profile in Section 5.
The physical implications of our observations are discussed in
Section 6. Finally, we summarize our results in Section 7. In this
paper, we assume a flat ΛCDM cosmology (e.g., Planck Colla-
boration et al. 2014) with H0 = 70 km s−1
Mpc−1
, ΩM = 0.3, and
ΩΛ = 0.7, and we adopt values of MBH = 2.6 × 108
Me and a
viewing angle of θ = 9°33
for the 3C 273 jet.
2. Observations and Data Analysis
2.1. GMVA 86 GHz
We observed 3C 273 with the GMVA at 86 GHz (λ ∼ 3.5
mm) on 2017 April 3 (project code MA008), as one of the first
31
https://www.physics.purdue.edu/MOJAVE/index.html
32
Li et al. (2022) reported a new estimation of BH mass of ∼ 109
Me and
viewing angle of ∼ 5° for 3C 273 during the review process of our paper.
These new estimates are based on a joint analysis of spectroastrometric data in
Gravity Collaboration et al. (2018) and new data from reverberation mapping
with a more generalized model. We confirm that these estimates do not affect
our main results and conclusions.
33
Previous studies have reported various values for the viewing angle of the
3C 273 jet. Jorstad et al. (2017) reported θ ∼ 6° from VLBI monitoring at
43 GHz. Meyer et al. (2016) showed the possible range of 3°
.8–7°
.2. However,
other studies have reported larger values of θ 10° (Savolainen et al. 2006;
Gravity Collaboration et al. 2018). Therefore, we assume θ = 9°, which is
broadly consistent with previously reported values of jet viewing angles.
2
The Astrophysical Journal, 940:65 (17pp), 2022 November 20 Okino et al.
3. VLBI observations with ALMA (see Goddi et al. 2019, for a
detailed description). The phased ALMA, eight VLBA stations,
and four European stations participated in our observation, as
summarized in Table 1. 3C 273 and calibrators (3C 279) were
observed for a track of ∼16 hr, almost a full track for the given
observing array. ALMA participated for ∼5.2 hr in the middle
of the track, providing baselines to both VLBA and European
stations. Data were recorded at a total bandwidth of 256 MHz
per polarization, which was further subdivided into four
58 MHz intermediate frequencies (IFs) of 116 channels each.
Data were correlated using the DiFX correlator (Deller et al.
2011) at the Max Planck Institute for Radio Astronomy in
Bonn, Germany. We note that Maunakea (MK) did not provide
robust fringe detections on any of the observed sources because
of the bad weather at MK throughout the GMVA campaign
during spring 2017 (see also Issaoun et al. 2019). We also note
that the visibility phases of PV baselines at each subband IF
had an instrumental offset of 180° in subsequent channels of
32 MHz widths owing to a misconfiguration of the subband
alignment in the correlation stage.
Initial data calibration was performed using the Astronom-
ical Image Processing System (AIPS; Greisen 2003). Preced-
ing standard calibration, the inner-IF phase offsets in the PV
baselines were corrected using a manually created bandpass
table. Visibility amplitudes were a priori calibrated in the
standard manner; visibilities at each baseline were first nor-
malized with the available autocorrelation spectra and then
scaled with the system-equivalent flux densities of the
corresponding stations.
Phases were calibrated in a standard manner with multiple
fringe-fitting runs after parallactic angle correction. First, the
instrumental phases stable across the track, such as phase
bandpass, inter-IF phase, and delay offsets, were corrected with
a scan of 3C 273, providing strong detection to all stations
except MK. This enabled coherent integration across the entire
bandwidth and more sensitive fringe-fitting by combining all
IFs. Second, the delay and rate offsets of each scan were
calibrated at the solution interval of the scan length, which is
typically several minutes. Then, short-timescale phase rotations
were fringe-fitted at solution intervals of 10 s.
The new addition of ALMA to GMVA has significantly
improved the overall array performance. Figure 1 shows the uv
coverage for our GMVA observation of 3C 273. The long
baselines beyond ∼1.5 Gλ in north–south (N–S) direction
correspond to ALMA. The phased ALMA has improved the
angular resolution of the GMVA observations in the N–S
direction by more than a factor of two (see Section 5.1). Fur-
thermore, ALMA provides detection at very high signal-to-
noise ratio on long baselines to both VLBA and European
stations at ∼1.5–2.0 Gλ (Figure 2). The sensitive ALMA
secured the detection of fringes to most of the stations in the
array while it was participating in the observation.
2.2. HSA 15/22/43 GHz
We performed multifrequency observations of 3C 273 at 15,
22, and 43 GHz with the High Sensitivity Array (HSA) on
2017 March 26, eight days before our GMVA observations
(project code: BA122). The observing array consisted of the 10
VLBA stations and the 100 m Effelsberg (EB) telescope in
Germany, as summarized in Table 1. Full-track observations
were performed for ∼11 hr, of which EB participated in the
first ∼3.4 hr. Data were recorded at dual circular polarizations
with four 64 MHz IFs subdivided into 256 channels, providing
Table 1
Summary of Observations of 3C 273
Array Project Code Stations Frequency Obs. Date Beam Size Geometric Mean
(GHz) (yyyy/mm/dd) (mas × mas, deg) (mas)
(1) (2) (3) (4) (5)
VLBA BH151 VLBA(10) 1.667 2008/02/02 10.312 × 4.460, −4.3 6.778
HSA BA122 EB+VLBA(10) 15.368 2017/03/26 1.025 × 0.408, −6.3 0.647
HSA BA122 EB+VLBA(10) 23.768 2017/03/26 0.577 × 0.273, −3.1 0.397
HSA BA122 EB+VLBA(10) 43.168 2017/03/26 0.325 × 0.128, −6.1 0.204
GMVA MA008 AA+EB+ON+PV+YS+VLBA(8) 86.268 2017/04/03 0.061 × 0.052, −42.7 0.057
Note. (1) The stations that participated in the observations. The two-letter codes for each station are as follows: ALMA (AA), Effelsberg (EB), Onsala (ON), Pico
Veleta (PV), Yebes (YS), Brewster (BR), Fort Davis (FD), Hancock (HN), Kitt Peak (KP), Los Alamos (LA), Maunakea (MK), North Liberty (NL), Owens Valley
(OV), Pie Town (PT), and St. Croix (SC). Ten VLBA stations (BR, FD, HN, KP, LA, MK, NL, OV, PT, and SC) are included in VLBA(10), and eight stations,
excluding HN and SC, in VLBA(8). (2) The observed central frequency. (3) The observing date. (4) Sizes of the major/minor axes and position angles of the
synthesized beam with uniform weighting. (5) The beam size of an equivalent circular Gaussian with the same beam solid angle derived from the geometric mean of
the major- and minor-axis beam sizes.
Figure 1. uv coverage of the GMVA observation at 86 GHz. Baselines to
ALMA are shown in red. Data are averaged at 60 s.
3
The Astrophysical Journal, 940:65 (17pp), 2022 November 20 Okino et al.
4. an aggregate of 256 MHz per polarization. Data were correlated
using the VLBA DiFX correlator.
The initial data calibration for the HSA data was performed
using AIPS. We note that the EB baselines in several IFs
showed lower visibility amplitudes and larger scattering in
visibility phases due to the bandpass issue, which cannot be
calibrated in this stage. These data were removed prior to the
data calibration. Data were calibrated in a standard manner
similar to the GMVA data sets described in Section 2.1;
amplitudes were a priori calibrated, and then phases were
calibrated with fringe-fitting. Fringes were detected on all sta-
tions, and similar baseline coverages were obtained at all three
observing frequencies.
2.3. VLBA 1.7 GHz
To complement our data on the larger-scale jet structure, we
reduced an archival VLBA 1.7 GHz data set of 3C 273
observed in 2008 February (project code: BH151). The data set
has one of the best hour-angle coverage among existing
archival data sets at 1.7 GHz.34
Data were reduced in a standard
manner in AIPS. Fringes were detected on all 10 VLBA sta-
tions, as summarized in Table 1.
3. Imaging
We reconstructed multifrequency images of 3C 273 from the
GMVA, HSA, and VLBA data sets presented in Section 2 with
regularized maximum likelihood (RML) methods implemented
in SMILI (Akiyama et al. 2017a, 2017b). Our GMVA and
HSA arrays are heterogeneous and were expected to have more
residual calibration errors at higher frequencies, such as 43 and
86 GHz. Furthermore, our GMVA observations had sparse uv
coverages lacking intermediate baselines as shown in Figure 1.
The traditional iterative hybrid mapping using CLEAN (e.g.,
Högbom 1974) with self-calibration implemented in popular
packages such as AIPS and Difmap (Shepherd 1997) is
generally more challenging than for the lower-frequency data
sets and does not offer the flexibility. RML methods provide a
more flexible imaging framework, by directly using various
types of data sets including robust closure quantities (e.g.,
Thompson et al. 2017) and a wider range of assumptions for
the source images.
We employed an imaging approach inspired by recent Event
Horizon Telescope (EHT) imaging of M87 (Event Horizon
Telescope Collaboration et al. 2019b) that explored a wide
range of parameters, implying assumptions of source images,
and assessed uncertainties in images and their deliverables
more conservatively. Using a scripted RML imaging pipeline,
we explored the distribution of images giving a satisfactory fit
to the data, which were all further used in the image analysis in
Section 4. We briefly introduce the RML method in Section
3.1. Then, we describe the imaging pipeline used in our ima-
ging of 3C 273 in Section 3.2, and the details of the imaging
parameter survey in Section 3.3.
3.1. RML Methods
RML methods are a new class of imaging techniques that
were conceived to overcome many of the technical challenges
of millimeter VLBI imaging, particularly with the EHT. RML
imaging takes a forward-modeling approach inspired by
Bayesian statistics, directly solving for an image without using
a dirty beam or dirty map. RML methods have been demon-
strated to improve the overall quality of image reconstruction
not only for synthetic observations (e.g., Honma et al. 2014;
Chael et al. 2016, 2018; Akiyama et al. 2017a, 2017b; Kur-
amochi et al. 2018) but also for actual interferometric mea-
surements with VLBI arrays (e.g., Event Horizon Telescope
Collaboration et al. 2019b; Issaoun et al. 2019; Kim et al. 2020;
Janssen et al. 2021) and connected interferometers (e.g., Mat-
thews et al. 2018; Yamaguchi et al. 2020).
RML methods derive a reasonable or conservative image
from an infinite number of images consistent with given
interferometric measurements by solving for an image that
minimizes the sum of data consistency metrics, such as χ2
terms, and regularization functions that mathematically
describe prior assumptions for the source morphology. This
framework allows a flexible choice of input data, for instance,
the direct use of closure quantities free from antenna-based
calibration errors (e.g., Chael et al. 2016, 2018; Akiyama et al.
2017b; Blackburn et al. 2020) and further inclusion of various
observing effects such as systematic non-closing errors (Event
Horizon Telescope Collaboration et al. 2019b). Popular reg-
ularization functions include ℓ1-norm, total variation (TV), and
total squared variation (TSV), enforcing sparsity in some basis
of the image (Honma et al. 2014; Ikeda et al. 2016; Akiyama
et al. 2017a, 2017b; Kuramochi et al. 2018) and the informa-
tion entropy of the image (e.g., Chael et al. 2016). By com-
bining various regularization functions, RML methods can
explore a wide range of images consistent with the data, often
leading to reconstruction with more reasonable assumptions of
the target source (e.g., Akiyama et al. 2017a, 2017b; Event
Horizon Telescope Collaboration et al. 2019b). Further tech-
nical and mathematical details of the RML approaches adopted
in this study are described in Event Horizon Telescope Colla-
boration et al. (2019b).
3.2. Imaging Pipeline
We used a scripted pipeline in Python for our RML imaging
with SMILI. In the pipeline, 3C 273 images were recon-
structed from AIPS-calibrated data (see Section 2) by utilizing
Figure 2. The signal-to-noise ratios of visibilities on 3C 273 as a function of
projected baseline length. Data are averaged at 60 s. Baselines to ALMA are
shown in red.
34
We cross-checked archival data of a more close-in-time VLBA observation
at 1.6 GHz in 2014 with the experiment code of BG216H. We obtained a jet
width profile consistent with the data sets used in this paper, confirming that the
width of the 1.6 GHz jet does not change significantly over the timescale of
10 yr.
4
The Astrophysical Journal, 940:65 (17pp), 2022 November 20 Okino et al.
5. weighted-ℓ1, TV, TSV, and maximum entropy method (MEM)
regularizers (see Appendix A of Event Horizon Telescope
Collaboration et al. (2019b) for mathematical definitions). The
pixel size of the image is typically set to one-tenth of the mean
FWHM size of the uniform-weighted synthesized beam sum-
marized in Table 1. Prior to imaging, the uv coordinates of the
data were rotated by 45° counterclockwise, resulting in the
same rotation of the image-domain axis, and the horizontal axis
approximately aligned with the jet direction. This allows us to
use a narrower rectangular field of view of the image and
minimizes the computational cost of imaging. Then, the visi-
bilities were coherently averaged for 60 s, after manually
flagging outliers. If specified, systematic errors were added in
quadrature to the thermal noise of the time-averaged complex
visibilities to account for non-closing errors. We explored 0 or
1% of non-closing errors within the range expected for polar-
ization leakages (e.g., Zhao et al. 2022).
Our imaging procedure is iterative, with four stages of
imaging and self-calibration. In the first stage, the initial image
is set to a circular Gaussian with the size corresponding to the
geometric mean of the major and minor-axis sizes of the syn-
thesized beam at each observed frequency (see Table 1). The
subsequent stages of imaging started with the final image of the
previous stage convolved with the above circular Gaussian.
The first two stages begin with the initial image and use visi-
bility amplitudes, log closure amplitudes, and closure phases
for imaging. At each stage, the visibility amplitudes of all
baselines added a 5% error in quadrature to the thermal noise to
account for the amplitude calibration uncertainties. In the final
two stages, the imaging uses complex visibilities and closure
quantities.
3.3. Imaging Parameter Survey
Using the pipeline described in Section 3.2, we explored a
wide range of parameters, as summarized in Table 2. At each
frequency, the parameter survey examined several tens to a few
hundred parameter sets with four to five parameters: potential
systematic non-closing errors (denoted as Sys. Error) and the
regularization parameters for the ℓ1
w
, TV, TSV, and MEM
regularizers. Among the sets of imaging parameters explored,
we selected “top sets” of the parameters that provide recon-
structed images with reasonable fits to data. The distributions
of the corresponding top-set images allow us to assess and
identify the morphologies commonly seen and insensitive to
the imaging choices as well as their uncertainties among the
reconstructed images consistent with our interferometric
measurements.
We started imaging with the HSA data at 15 GHz. We
adopted the published VLBA image at 15 GHz and Stokes I on
2017 May 25 (project code BL229AH) from the MOJAVE
program (Lister et al. 2018), which was the closest epoch to our
HSA observations, as the soft mask of the imaging region with
ℓ1
w
regularization. This allows noise suppression outside of the
area, which has historically had no significant emission.35
Then, the best-fit image among the top-set 15 GHz images is
adopted as the soft mask for subsequent 22 GHz image pro-
cessing to maximize the consistency between adjacent fre-
quencies. We processed data at higher frequencies (43 and
86 GHz) in the same manner using best-fit images at the
adjacent lower frequencies. For L-band data, we used the L-
band VLBA image in Akiyama et al. (2018) as its soft mask.
We selected the top-set images with good fits to the data
using χ2
statistics. For the selection of top-set parameters, we
adopted the minimum threshold of 1.5 for the reduced χ2
values of full complex visibilities, amplitudes, and closure
quantities of self-calibrated images. Consequently, 15 to 45
images were selected at each frequency, as summarized in
Table 2, and used in post-imaging analysis.
3.4. Total Flux Scaling for GMVA 86 GHz
The overall scaling of visibility amplitudes depends strongly
on the accuracy of the a priori calibration of visibility ampli-
tudes based on measurements of the system-equivalent flux
density at each station, which often have large systematic errors
in high-frequency VLBI observations above ∼86 GHz (see,
e.g., Koyama et al. 2016; Kim et al. 2018, for previous GMVA
observations). We assumed Effelsberg (EB) and Pico Veleta
(PV), often considered as reliable stations for a priori calibra-
tions, as the reference stations for overall gain scaling (see, e.g.,
Angelakis et al. 2015; Fuhrmann et al. 2016; Agudo et al.
2018). We scaled the total flux density of our GMVA 86 GHz
images such that the median gain amplitude of EB and PV is
unity. The derived scaling factor is ∼1.46, and we obtained the
scaled total flux (median in the top set) as ∼3.1 Jy. The scaling
of amplitudes and the total flux density described here will not
affect our main results based on the collimation profile mea-
sured from the source morphology (Section 4.2). We note that
our 86 GHz images show reasonable spectral indices to images
at lower frequencies (see Section 5.3).
4. Image Analysis
With all top-set images from the imaging parameter survey
(Section 3.3), we investigate the jet profile as a function of
distance from the central black hole. First, we identified the
position of the central black hole using the core shift effect as
described in Section 4.1. Then, the jet radii at each frequency
were measured, as described in Section 4.2.
Table 2
List of Imaging Parameters
Freq. Sys. Error ℓ1
w
TV TSV MEM Total No. of No. of Top-set
(GHz) (%) Parameters Parameters
1.6 0, 1 1 1 0, 10−2
, 10−1
, 1, 10 0, 10−2
, 10−1
, 1 40 15
15 0, 1 10−1
, 1, 10 1 0, 10−2
, 10−1
, 1, 10 0, 10−2
, 10−1
, 1, 10 150 45
22 0, 1 10−1
, 1, 10 1 0, 10−2
, 10−1
, 1, 10 0, 10−2
, 10−1
, 1, 10 150 30
43 0, 1 10−1
, 1, 10 1 0, 10−2
, 10−1
, 1, 10 0, 10−2
, 10−1
, 1, 10 150 35
86 0, 1 10−1
, 1 1 0, 10−2
, 10−1
, 1 0, 10−2
, 10−1
, 1 64 24
35
The typical jet proper motion of 3C 273 is a few mas yr−1
, which does not
change the overall jet emission structure in a few months.
5
The Astrophysical Journal, 940:65 (17pp), 2022 November 20 Okino et al.
6. 4.1. Core Shift Measurements
Core shift is a positional shift of the radio core between two
different observing frequencies due to the frequency depend-
ence of the optical depth of the synchrotron self-absorption
(Blandford & Königl 1979). In our study, we employed the
widely used self-referencing method (e.g., Lobanov 1998;
O’Sullivan & Gabuzda 2009; Pushkarev et al. 2012; Fromm
et al. 2013; Hada et al. 2018) to measure the core shift of
3C 273, based on a well-vetted assumption that the emitting
regions from the extended jet are optically thin features, and
their positions do not change at different frequencies. From this
assumption, one can obtain the core offset values between two
images at different frequencies after aligning the corresponding
optically thin emission regions. We only used the images at 15,
22, 43, and 86 GHz observed within a week (see Table 1). The
offsets were measured for four combinations (15/22, 22/43,
43/86, 15/43 GHz).36
For each frequency pair, we derived the
offsets using all combinations of the top-set images and
adopted their mean values as the measured offsets.
First, we needed to identify the core position for each jet
image to compare them at different frequencies. We decided on
the locations of some components in the upstream regions by
several circular Gaussian model fittings using Difmap. We
applied this analysis to all the top-set images and identified four
to seven components for the 15–86 GHz images. We set the
core at the most upstream component for each image.
To obtain the core offset between two frequencies, we used a
two-dimensional cross-correlation of the optically thin emis-
sion regions in the jet images following the widely used
method described in Croke & Gabuzda (2008). First, the pixel
size of both images was set to a twentieth of the restoring beam
size at the lower frequency, which was much smaller than the
angular resolution at both frequencies. Next, we convolved
both images with the restoring beam at the lower frequency.
After masking the optically thick core regions of both images,
we computed the cross-correlation coefficient rxy defined by
( ¯ )( ¯ )
( ¯ ) ( ¯ )
( )
=
S S - -
S S - S S -
n n n n
n n n n
= =
= = = =
r
I I I I
I I I I
1
xy
i
n
j
n
ij ij
i
n
j
n
ij i
n
j
n
ij
1 1 1, 1 2, 2
1 1 1, 1
2
1 1 2, 2
2
where Iν,ij is the intensity at pixel (i, j) at frequency ν, and ¯
I is
the averaged intensity in the calculated region. The cross-cor-
relation coefficient rxy is a function of the relative positional
offset (Δx, Δy). The positional shift between two images at
frequencies ν1 and ν2 is given by the location of the global
maximum rxy. The core offset was defined as the remaining
positional offset of the peaks after aligning the corresponding
optically thin emission regions.
4.2. Jet Profile Measurements
We investigated the jet collimation in 3C 273 using multi-
frequency images. Prior to analysis, we cut off the brightness
distribution for all the images below the rms values (see
Section 5.1) at each frequency to remove the noise outside the
jet regions. Then, the jet radius was measured as a function of
distance from the core at each frequency in two steps.
First, we measured the position angle (PA) of the jet at each
distance from the core. Following Pushkarev et al. (2017), we
took a circular slice of the image centered at the core with a
radius corresponding to each distance and adopted the inten-
sity-weighted centroid as the PA of the jet at the corresponding
distance.
After deriving the PA, we measured the jet radius at each
distance. Because the jet bends on milliarcsecond scales, we
examined two ways of slicing the image to measure the jet
radius. The first one is to take a slice perpendicular to the PA at
each distance, and the other is to slice the image perpendicular
to the local tangent line of the PA profile, following Pushkarev
et al. (2017). The effective jet radius was measured by taking
the second moment σw of the cross section along with each
slice at each distance. Then, the FWHM of the jet was obtained
as s
=
FWHM 2 2 ln 2 w. We derived the deconvolved
FWHM (w) defined as q
= -
w FWHM2
beam
2
, correcting the
blurring effects with the restoring beam at the FWHM of
θbeam
37
(see Table 1). Finally, the jet radius r at each distance
was obtained from half the size of the deconvolved FWHM
(i.e., r = w/2).
The jet radius profile was measured with an interval of half of
the restoring beam size (see Table 1). We only accept mea-
surements of jet radius that satisfy the following three criteria: (i)
the FWHM is larger than θbeam so that the vertical jet emission is
well resolved, (ii) the distance from the radio core is greater than
2 × θbeam to conservatively remove the effect of the unresolved
core, and (iii) the peak intensity of the slice is three times larger
than the mean of the residual rms noise derived from all top-set
images (see Section 5) at each frequency except for 22 GHz. At
22 GHz, instead, the threshold was set to be nine times larger
than the mean residual rms noise to make reliable measurements
only at bright locations in the sparse intensity distribution (see
the image in Figure 5). The jet radius profile at each frequency
was measured for all top-set images with the above two slicing
methods. Then, the mean and standard deviation of the jet radius
at each distance and frequency were adopted as the corresp-
onding jet radius and its uncertainty, respectively.
5. Results
5.1. GMVA Image
In Figure 3, we show the mean total intensity image of the
3C 273 jet with GMVA at 86 GHz derived by averaging all
top-set reconstructions (24 images) obtained from the imaging
parameter survey in Section 3.3. Here we show the mean image
restored at two characteristic resolutions of our GMVA
observations equivalent to uniform weighting.38
Our new
image provides the sharpest view of the inner jet at 86 GHz
thanks to the critical addition of ALMA. Without ALMA, the
corresponding beam sizes will be 265 × 50 μas in uniform
weighting, providing significantly worse resolutions along the
N–S direction by a factor greater than 2.5. The spatial resolu-
tion of our observations is also higher than that of previous
36
The other two (i.e., 15/86 and 22/86 GHz) pairs were omitted due to the
lack of extended emission commonly seen at both frequencies.
37
Although interferometric imaging with RML, in principle, does not require
a post-imaging beam convolution to obtain piecewise smooth images, the raw
image may contain some over-resolved features that are not strongly supported
by data. To reduce potential bias from such features, in this work, we adopt the
conventional approach that derives deconvolved widths from ones measured
from beam-convolved images widely used with CLEAN imaging.
38
The restoring beam is arbitrary for RML methods, given that the nature of
methods is such that the synthesized beam is not used for deconvolution. Data
weighting is equivalent to the natural weighting of CLEAN imaging since data
are only weighted by thermal noise and not by uv density, while the recon-
structed images are known to have a high fidelity at the resolution comparable
to, or higher than, uniform weighting.
6
The Astrophysical Journal, 940:65 (17pp), 2022 November 20 Okino et al.
7. observations, such as the high-sensitivity VLBA + GBT
observations in Hada et al. (2016) with a resolution of
340 × 110 μas at PA = −10°. The high resolution of our new
observation allows us to resolve the vertical structure of the
inner jet within a few milliarcseconds from the core at 86 GHz
for the first time.
To assess the image uncertainty quantitatively, we obtained
residual images using the top-set reconstructions (not blurred)
as the image models in the Difmap software. We calculated
the image rms values for each residual in the top set, and
derived the mean value of ∼3 mJy beam−1
as the representative
image uncertainty at 86 GHz with a natural weighting scheme.
We then determined the lowest contour level for the uniform-
weighting beam to be the same dynamic range (∼100) as the
one for natural weighting.
In addition, the final top-set reconstructions have some
variations in the image domain depending on the imaging
parameters. Figure 4 shows the standard deviation image of
GMVA 86 GHz across the top-set reconstructions. The
brightest core shows the largest emission (∼200 mJy beam−1
),
while the faint and extended emissions show smaller variation.
These results suggest that the variability in the image domain,
especially in the bright region, is dominated by the choice of
imaging parameter rather than the rms of the residual images.
The median value of the scaled total flux densities among the
top sets of 86 GHz images is ∼3.1 Jy (Section 3.4),
corresponding to ∼30% of the arcsecond-scale core flux den-
sity measured with ALMA in Band 3 during this GMVA
campaign (Goddi et al. 2019). The extended jet emission at 3
mm is broadly consistent with the 7 mm jet, implying optically
thin spectra (see Section 5.3) and suggesting that the rest of the
ALMA core flux density has been resolved out at the shortest
VLBI baselines with fringe spacings equivalent to a few
milliarcseconds.
5.2. HSA and VLBA Images
In Figure 5, we show lower-frequency images of 3C 273
observed with the HSA and VLBA, which were all averaged
over the top-set reconstructions similar to the GMVA images in
Figure 3. The overall jet morphology is consistent with pre-
vious ground-based (MOJAVE: Lister et al. 2018; VLBA-BU-
Blazar39
: Jorstad et al. 2017) and space-based VLBI observa-
tions (Radio Astron: Bruni et al. 2017, 2021). Regardless of the
observing frequency, the 3C 273 jet extends in the southwest
direction with multiple bright knots whose relative locations
are consistent between different frequencies.
The HSA 43 GHz image shows the inner jet structure within
∼2 mas, and two extended components around 4 and 7 mas
from the core. These overall morphology is consistent with a
Figure 3. The inner-jet image of 3C 273 obtained with the GMVA observation including ALMA at 86 GHz. Here we show the mean of the top-set reconstructions
restored at the resolution with a uniform weighting scheme. The image is restored with a circular beam of 57 μas (indicated in the bottom left corner) corresponding to
the geometric mean of the uniform-weighting beam of 61 × 52 μas. The peak intensity is 0.69 Jy beam−1
. The contours are multiplies by factors of 2, from the lowest
contour level of 6.5 mJy beam−1
.
39
http://www.bu.edu/blazars/VLBAproject.html
7
The Astrophysical Journal, 940:65 (17pp), 2022 November 20 Okino et al.
8. close-in-time image in the database of the VLBA-BU-Blazar
program observed a week previously (2017 March 19).
The HSA 15 and 22 GHz images show the same regions
with a bright core and extended jet emissions up to ∼25 mas
from the core. One can see that the direction of the jet changes
at ∼10 mas from the core, with the PA changing from ∼−140°
(upstream) to ∼−120° (downstream). In the jet, several
components are located at the same position at both fre-
quencies. However, the faint jet component is not detected at
22 GHz unlike at 15 GHz, due to the optically thin synchrotron
emission from the jet (see Section 5.3) and also the limited
uv coverage for short baselines at 22 GHz compared with
15 GHz.
In our VLBA 1.7 GHz image, the jet emissions downstream
of ∼20 mas are reconstructed with our imaging. The image is
similar to the 3C 273 jet shown in Kovalev et al. (2016) at the
same frequency band. One can see the bright component
at ∼40 mas and the extended jet emission at ∼100 mas from
the core.
5.3. Spectral Index Maps
We measured the spectral index (defined α as Iν ∝ να
) of the
jet emission between two adjacent frequency bands. To derive
the spectral index map for each pair of images, we first aligned
the two images by adopting the offset determined by the two-
dimensional cross-correlation (see Section 4.1). Then, the
spectral index maps were derived for all possible pairs of top-
set images at two frequencies. Then, we averaged over all
spectral index maps for each frequency pair to create the mean
spectral index map.
In Figure 6, we show the mean spectral index map of the
3C 273 jet for each pair of neighboring frequency bands. In all
frequency pairs, the 3C 273 jet consistently shows spectra that
are optically thick upstream of the core, become flat near the
core, and then become optically thin downstream. These fea-
tures are commonly observed in radio jet sources (e.g., Hovatta
et al. 2014), therefore suggesting that the core offsets derived in
Section 4.1 are plausible.
5.4. Core Shift
In Table 3, we show the measured core offsets for each pair
of frequencies. The measured offsets are in the x-direction,
parallel to the large-scale jet axis. The standard deviations of
the measured offsets are the same or less than the pixel sizes of
the regridded images used for these measurements. Therefore,
the measured offsets do not depend on the different combina-
tions of imaging parameter sets used to reconstruct the top-set
images.
We fit a power-law model of the core shift caused by the
synchrotron self-absorption of the jet emission (e.g., Lobanov
1998). We assume that the core location at the frequency νi
relative to the 86 GHz core is given by
( ) ( )
n n
D = -
- -
x A , 2
i x i
k k
86
( ) ( )
n n
D = -
- -
y A , 3
i y i
k k
86
for each direction, where ν86 = 86.3 GHz. The power-law
index k depends on the optically thin spectral index of the
synchrotron emission, magnetic field, and particle density
distributions. Assuming a conical jet with a constant velocity
and in the equipartition state between magnetic and particle
energy densities, k ≈ 1 has been shown from the synchrotron
self-absorption model proposed by Blandford & Königl (1979),
which was confirmed in many sources by previous core shift
measurements (see also Pushkarev et al. 2012, and references
therein). For 3C 273, Lisakov et al. (2017) has performed
multiepoch core shift measurements and reported values of k
close to 1 for each epoch. Therefore, given the small sets of
frequency pairs available in the presented observations, we
assume k = 1 and only derive coefficients (Ax, Ay) in our
analysis.
In this model, the positional offsets (μx, μy) of the radio cores
between each frequency pair (νi, νj) are described as
( ) ( )
m n n
= D - D = -
- -
x x A , 4
x i j x i
k
j
k
( ) ( )
m n n
= D - D = -
- -
y y A . 5
y i j y i
k
j
k
We derive the best-fit model parameters by comparing the
model offsets above with measured ones through the least-
squares fitting based on χ2
defined by
⎧
⎨
⎩
⎫
⎬
⎭
⎧
⎨
⎩
⎫
⎬
⎭
( )
( )
( )
( )
( )
c
n n m
s
n n m
s
= å
- -
+ å
- -
- -
- -
A
A
. 6
i j
x i
k
j
k
x
x
i j
y i
k
j
k
y
y
2
,
2
,
2
We found the best-fit parameters of Ax = −5.635 ± 2.424
and Ay = 0.278 ± 2.424, which minimize χ2
. The errors here
indicate a 68.3% confidence interval derived from the χ2
sur-
face. With these values, Equations (2) and (3) can be used to
derive the location of the upstream end of the jet, often con-
sidered the black hole position (e.g., Hada et al. 2011), by
Figure 4. Standard deviation of the top-set reconstructions of GMVA 86 GHz
restored with the circular Gaussian beam of 57 μas shown by the white circle in
the bottom left corner. The contours represent the mean image shown in
Figure 3.
8
The Astrophysical Journal, 940:65 (17pp), 2022 November 20 Okino et al.
9. taking νi → ∞. From the best-fit parameters, we obtained the
location of the jet apex at x0 = 65 μas and y0 = −3 μas
upstream40
of the 86 GHz core for 3C 273. Figure 7 shows the
resultant core positions along the large-scale jet axis (i.e., x-
direction). The lower-frequency core is located at a greater
distance from the central black hole, as anticipated for the core
shift caused by synchrotron self-absorption (Blandford &
Königl 1979; Lobanov 1998).
5.5. Jet Collimation Profile of 3C 273
Figure 8 shows the radius and position angle profile of the
3C 273 jet as a function of the deprojected distance from the
central black hole. Our VLBI measurements cover depro-
jected distances ranging from ∼105
Rs to ∼108
Rs. The radius
profile at each frequency smoothly connects. Near z ∼ 107
Rs,
the jet radius profile shows a sharp increase by a factor of ∼2,
where the PA of the jet sharply changes by ∼20° to the
north. The overall PA profile meanders around the mean PA
of −138°, coinciding with the large-scale jet (Conway
et al. 1993).
The jet radius profile in the outer region beyond ∼ 107
Rs is
steeper than that in the inner region. Thus, we fit the power-law
functions to the jet radius profile to quantify the jet shape in
each region. The details of our model selection are described in
the Appendix.
Here, we excluded the region from 4 × 106
Rs to 107
Rs (the
gray shaded region in Figure 8) from our fitting analysis
because of its peculiar and complex morphologies not seen in
the rest of the jet. In Figure 9, we show the streamline of the jet
image of HSA 15 GHz to illustrate the region that we excluded
from our fitting analysis. This region shows a rapid swing in
the streamline from the global position angle, and simulta-
neously the vertical profiles of the jet show highly asymmetric
ridge-like structures not seen in the rest of the global jet. These
peculiar morphologies make it difficult to define and measure
the width of the jet in a consistent way with the rest of the
global jet.
First, we model the jet radius r(z) with a couple of single
power-law functions (r(z) ∝ za
), separately fitting to each of the
upstream (z < 4 × 106
Rs) and downstream (z > 107
Rs)
regions. The best-fit values and associated uncertainties of the
parameters are estimated using the percentile bootstrap method,
where in each trial the parameters are derived by applying an
unweighted least-squares method to the data sets randomly
resampled from the original data, allowing duplication. After
10,000 bootstrap trials, we adopt the median values as the best-
fit parameters, and one-third of the 99.7% percentile confidence
intervals as their 1σ uncertainties. The power-law index is
found to be = -
+
a 1.28 0.05
0.08
, indicating a conical/hyperbolic
shape in the downstream region, whereas = -
+
a 0.66 0.05
0.04
is
indicative of parabolic collimation found in the upstream
region.
Furthermore, we also examine a joint fitting of both regions
with a broken power-law function defined by
⎜ ⎟
⎡
⎣
⎢
⎛
⎝
⎞
⎠
⎤
⎦
⎥
( ) ( )
( )
( )
/
/
= +
-
-
r z R
z
z
2 1 7
a a
a a
0
2
b
2
u d
u d
following Nakahara et al. (2018). R0 is the scale factor, zb is the
location of the break, and au and ad are the power-law indices
of the upstream and downstream regions, respectively. Here s is
the parameter controlling the sharpness of the curvature at the
transition point, which is fixed to be s = 10. The best-fit
parameters and their errors are derived using the bootstrapping
method in the same manner. The power-law indices in the
downstream and upstream regions are found to be
= -
+
a 1.31
d 0.06
0.10
and = -
+
a 0.67
u 0.04
0.02
, respectively, which are both
consistent with the results of the above double power-law fit-
ting. The jet shape transition is found to occur at
= ´
-
+
z R
1.1 10
b 0.2
0.1 7
s. These results show that the 3C 273 jet
has a transition in its shape from semiparabolic to conical/
hyperbolic at the deprojected distance of ∼107
Rs from the
central black hole.
6. Discussion
6.1. Nature of the Jet Collimation in 3C 273
Our new quasi-simultaneous observations clearly show the
transition of the jet shape from semiparabolic to conical/
hyperbolic at ∼107
Rs from the central black hole, providing
the first compelling example of a collimation break in a quasar
jet. Interestingly, the transitional location roughly coincides
with the region at ∼4 × 106
to 107
Rs where the jet width (2r)
Figure 5. Multifrequency images of 3C 273 jets with the HSA at 43, 22, and 15 GHz and the VLBA at 1.7 GHz. Each panel shows the mean top-set image at each
frequency restored by the circular Gaussian beam with the beam solid angle of the uniform-weighting beam size in Table 1. The lowest contour levels are
6.5 mJy beam−1
at 43 GHz, 8.2 mJy beam−1
at 22 GHz, 7.1 mJy beam−1
at 15 GHz, and 11.6 mJy beam−1
at 1.7 GHz. The contours for all images are multiplied by
a factor of 2. The lowest contour level of each image is estimated from the mean residual image rms of the top-set reconstructions.
40
The location of the jet apex was derived for k = 1, and may vary by at most
a factor of two in the range k ∼ 0.8–1.2 constrained by Lisakov et al. (2017).
These uncertainties do not affect the main conclusions of this paper.
9
The Astrophysical Journal, 940:65 (17pp), 2022 November 20 Okino et al.
10. rapidly expands by a factor of ∼2 with significant bending,
which was not used in the fitting because of its peculiarity (see
Figure 9). Recent space-based VLBI observations with Radio
Astron at 1.6 GHz revealed the complicated limb-brightened jet
emission in this area (Bruni et al. 2021). Mertens & Lobanov
(2015) shows non-ballistic motions of jet components along the
northern and southern limbs over 14 years, which is longer than
the jet crossing time of this region considering the typical
proper motion of the jet (∼1 mas yr−1
, Lister et al. 2019). After
passing through the location of the collimation break, the
northern and southern limbs smoothly merge into a single limb,
and its position angle farther downstream is temporally and
spatially stable over 26 years of 15 GHz observations of the
MOJAVE program.41
The stability of the broadened, double-
ridge structure, apparently around the collimation break, sug-
gests a stationary magnetohydrodynamic feature, possibly
triggered by some changes in the circumjet environment
causing pressure mismatch with the jet (e.g., Mizuno et al.
2015), as the HST-1 knot in M87 near the collimation break is
indicated to be (Asada & Nakamura 2012).
The jet velocity field is another important physical quantity
that is closely related to jet collimation. This prediction is
supported by various VLBI observations of M87 (Nakamura &
Asada 2013; Asada et al. 2014; Park et al. 2019b, 2021) and
1H 0323+342 (Hada et al. 2018), and statistical studies of large
samples of AGN jets (Homan et al. 2015). In Figure 10, we
show the profile of the apparent jet velocities of 3C 273 from
long-term monitoring observations at 15 GHz by the MOJAVE
program (Lister et al. 2019) and at 43 GHz by the BU-Blazar
program (Jorstad et al. 2017), compared to the collimation
profile. Except for the stationary knot features at 1 mas
identified in the literature (Savolainen et al. 2006; Jorstad et al.
2005, 2017; Bruni et al. 2017; Lisakov et al. 2017), Figure 10
indicates that the jet has already been accelerated to relativistic
speed with an apparent velocity of at least ∼5c before the
collimation break. This trend in the 3C 273 jet differs from that
of M87, which shows gradual accelerations in the parabolic
regions and velocity saturation at the collimation break (Asada
Figure 6. Spectral index maps between pairs of neighboring frequencies labeled in the top right corner of each panel. Spectral index α is defined by Iν ∝ να
. Spectral
index values in each pair were calculated from all images in the top sets of both frequencies after aligning the images using cross-correlation (Section 4.1) and
averaging them. The contours in each panel represent the mean image of the lower frequency of the HSA as shown in Figure 5.
Table 3
Positional Offsets of the Core between Different Frequencies
ν1, ν2 N Pixel μx μy σx σy
(GHz) (mas) (mas) (mas) (mas) (mas)
(1) (2) (3) (4) (5) (6) (7)
15.4, 23.7 1350 0.032 0.000 0.036 0.032 0.032
23.8, 43.2 1050 0.020 −0.224 0.005 0.020 0.020
15.4, 43.2 1575 0.032 −0.129 0.032 0.032 0.032
43.2, 86.3 840 0.010 −0.077 −0.010 0.010 0.010
Note. (1) Frequency pairs. (2) Total number of combinations. (3) Pixel size of
regridded images used to measure offsets. (4) Mean offset in the x-direction. (5)
Mean offset in the y-direction. (6) Standard deviation of the offsets in the x-
direction. (7) Standard deviation of the offsets in the y-direction.
Figure 7. The core position along the large-scale jet axis as a function of the
frequency based on the fitted power-law model. The core positions, denoted by
the black dots, are relative to the 86 GHz core. The red line shows the best-fit
power-law model, and the black line shows the best-fit location of the central
black hole. The error bars of the best-fit core positions and the shaded area of
the best-fit model indicate the 68% confidence interval estimated from the χ2
surface of the fitted parameters (Section 5.4).
41
http://www.physics.purdue.edu/astro/MOJAVE/sourcepages/1226+023.
shtml
10
The Astrophysical Journal, 940:65 (17pp), 2022 November 20 Okino et al.
11. et al. 2014; Park et al. 2019a). Further observations of the jet
kinematics in both the inner (<1 mas) and outer (>10 mas)
regions would be useful for investigating the detailed velocity
field in the collimation zone of 3C 273 and would provide
useful comparisons to radio galaxies.
For the innermost jet at the inner subparsec scale, one can
compare our results with recent submilliarcsecond-scale
observations with near-infrared optical interferometry. 3C 273
has been intensively studied with the Very Large Telescope
Interferometer, which recently resolved the broad-line regions
(BLRs) with a size of 46 μas ∼ 0.1 pc as an ionized gas disk
(Gravity Collaboration et al. 2018), and the dust torus emission
with a size of ∼150 μas ∼ 0.4 pc (Gravity Collaboration et al.
2020). The innermost collimation profile of the 3C 273 jets,
expected by extrapolating to a farther inner region, is smaller
than the measured geometry of the resolved BLRs and hot dust
torus distributions. Such a region, where the jet is surrounded
by the BLRs and dust torus, would be reachable with future
higher-frequency observations, such as with the EHT at 230 or
345 GHz. Future higher-frequency VLBI observations will be
critical for understanding the role of such an external medium,
which is common in quasars in jet collimation.
Figure 8. The radius and PA of the 3C 273 jet as a function of the deprojected distance from the central black hole. The deprojected distance from the central black
hole is derived using the best-fit core shift model at a viewing angle of i = 9° (see Section 1) for the black hole mass of MBH = 2.6 × 108
Me (Gravity Collaboration
et al. 2018). Upper panel: the jet radius profile. The colored circles and associated error bars indicate the mean values and standard deviations of the measurements,
respectively. Different colors show measurements from different observations, as shown in the legend. The solid and dashed lines show single power-law fits (r ∝ za
)
to the inner side, semiparabolic (a = 0.66), and to the outer side, conical/hyperbolic (a = 1.28), respectively. The surrounding shaded areas represent the uncertainty
of the single power-law fits (1σ, 2σ, 3σ). The green line represents the best-fit broken power-law function, giving the best-fit distance of the jet shape break of
zb = 1.1 × 107
Rs shown on the vertical dotted line. Lower panel: the jet PA profile. The color convention is the same as in the upper panel. The horizontal dashed line
shows PA = −138°, which is broadly consistent with the axis of the large-scale jet (e.g., Davis et al. 1985; Conway et al. 1993). The gray shade across both panels
shows the region excluded from the fitting analysis because of a large bending seen in the jet (see the details in Section 5.5).
11
The Astrophysical Journal, 940:65 (17pp), 2022 November 20 Okino et al.
12. Downstream of the collimation break, the jet structure up to
about the kiloparsec scale shows a conical/hyperbolic expan-
sion with a power-law index of a = 1.28. The unconfined
structures downstream of the jets have been found in other AGN
jets (Pushkarev et al. 2017; Kovalev et al. 2020). To investigate
the jet shape beyond the VLBI scales ( 1 kpc), we show
additional measurements based on CLEAN images from
MERLIN and Very Large Array (VLA) observations at 1.6 GHz
and 5 GHz from Akiyama et al. (2018) and Perley &
Meisenheimer (2017), respectively, in Figure 11. These addi-
tional measurements are obtained from the kiloparsec-scale
radio lobe at the terminal end of the 3C 273 jet. Although
previous observations detected the intermediate-scale (∼1″–
10″) jet emission between the central core and the kiloparsec-
scale lobe (e.g., Perley & Meisenheimer 2017), the transverse
structure is not well resolved, and the radius cannot be measured
reliably. This causes a lack of measurements at 108
–1010
Rs. The
inner semiparabolic line, if extrapolated, significantly under-
estimates the jet radius at the kiloparsec scale. On the other
hand, the jet radius at this scale is smaller than the extrapolated
conical/hyperbolic line, and these kiloparsec-scale jets can be
more conically connected to 1.7 GHz measurements. Future
observations of the intermediate scale would be useful for
constraining the propagation of the jet into the kiloparsec-scale
radio lobe and for investigating detailed jet features interacting
with the ambient ionized/molecular gas (Husemann et al. 2019)
and hot gas cocoons (Bromberg et al. 2011).
6.2. Comparison with Other AGN Sources
The jet structure has been investigated for many objects in
recent decades, and the transitions of jet collimation profiles
have been discovered in several jets of radio galaxies and BL
Lac objects. The presented results on 3C 273 have added the
case of a quasar jet. To compare our 3C 273 results with other
AGN jets, we show in Figure 12 the relation between the black
hole mass and the deprojected distance of the jet collimation
break for both 3C 273 and other AGN sources. The break
locations are widely distributed from ∼104
Rs to ∼108
Rs,
where 3C 273 is located on the further side.
A popular interpretation for the origin of the jet collimation
break is that the transition of the external pressure profile
Figure 9. One of the top-set images from HSA 15 GHz observation (gray
contours) overlaid with the streamline of the 3C 273 jet (filled and open cir-
cles). The regions excluded from our fitting are indicated by gray filled circles,
showing a stable complex and bending double-ridge-like morphology not seen
in the rest of the global jet (see Section 6.1). A black dashed line indicates the
global position angle of the jet estimated from the large-scale jet image (e.g.,
Davis et al. 1985).
Figure 10. The apparent velocity (top) and collimation profile (bottom) as
functions of the projected distance from the black hole. The black dotted line
represents the best-fit location of the collimation break.
Figure 11. The jet radius and PA profiles of the 3C 273 jet, extended from
Figure 8 to include measurements of the large-scale jet beyond the deprojected
distance of ∼200 kpc traced with VLA 5 GHz and MERLIN 1.6 GHz.
12
The Astrophysical Journal, 940:65 (17pp), 2022 November 20 Okino et al.
13. triggers the end of the jet collimation, where the external
pressure does not provide enough support to confine the jet
(e.g., Asada & Nakamura 2012; Tseng et al. 2016). For the
pioneering case of M87, Asada & Nakamura (2012) discussed
that the transition of the jet shape may result from the transi-
tional change in the external pressure profile of the circumjet
medium near the Bondi radius and the end of the sphere of
gravitational influence (SGI). This interpretation is motivated
by X-ray observations, which indicate that the different pres-
sure profiles of the ambient gas are realized inside and outside
the Bondi/SGI radius in M87 (Russell et al. 2015, 2018).
We further investigated the hot gas properties for other sources
to check whether similar conditions to those in M87 could be
established. However, the number of sources whose proximity to
the central core can be spatially resolved by X-ray observations
is limited, making it difficult to give accurate estimations of the
Bondi radii for those sources. Therefore, we consider the SGI
radius instead of the Bondi radius for the gravitational spheres of
the central black holes. Note that we checked the temperature of
the bright cores of several sources hosted by elliptical galaxies in
our collected samples and confirmed that the Bondi radii are
approximately of the same order of magnitude as the SGI radii42
(e.g., Sun 2009; Fujita et al. 2016).
Here, the SGI radius is estimated as s
= =
R GM d
SGI BH
2
( )( )
s
c R
1 2 d
2
s, where σd is the stellar velocity dispersion. To
investigate the relationship between the location of the SGI
boundary and the jet collimation break among our samples with
various BH masses, we introduced an empirical MBH–σd rela-
tion derived in Kormendy & Ho (2013). This relation is par-
ticularly strong for the classical bulge and elliptical galaxies,
and our sample is supposed to follow this relation (e.g., see
Table 2 in Kormendy & Ho 2013, and references therein).
Indeed, 3C 273 follows the relation from the stellar velocity
dispersion of σd = 210 km s−1
(Husemann et al. 2019) and
SMBH mass of MBH = 2.6 × 108
Me, which gives us an esti-
mation of the SGI radius as RSGI ∼ 106
Rs (see the solid line in
Figure 12).
The most important finding here is that the measured loca-
tions of the collimation breaks, including in 3C 273, are more
widely distributed than the intrinsic scatter of the SGI locations
seen in the samples of Kormendy & Ho (2013). In particular,
NGC 4261 (Nakahara et al. 2018), NGC 1052 (Nakahara et al.
2020), and NGC 315 (Boccardi et al. 2021; Park et al. 2021)
imply a transition of the jet collimation in a substantially more
inner area than the SGI boundary. For NGC 315, Park et al.
(2021) discussed that the nonrelativistic outflow, such as wind
from the accretion disk, may play a critical role in jet colli-
mation—for instance, the inner break of the jet collimation seen
in NGC 315 may occur if the wind does not reach the Bondi
radius or the edge of the SGI.
Figure 12. The relation between the black hole mass and the deprojected distance of the jet collimation break from the central engine. The red star shows our results
from the 3C 273 jet, and the cyan circles show results from other sources reported in the literature. The red horizontal bar indicates the region of a persistent feature
seen near the break distance with a complex bending double-ridge-like morphology potentially associated with the transition in the jet shape (see Figure 9 and
Section 6.1). To compare with the location of the SGI, we show the SGI locations of the classical bulges and elliptical galaxies in gray squares taken from Kormendy
& Ho (2013). The black solid line and gray shaded area are the best-fit model and the 1σ error range of the relation between the black hole mass and SGI location,
transformed from the MBH–σd relation in Kormendy & Ho (2013). The dotted lines show the actual distances in parsecs. The results of other sources are obtained from
the following references; M87: Asada & Nakamura (2012), NGC 6251: Tseng et al. (2016), NGC 4261: Nakahara et al. (2018), Cygnus A: Nakahara et al. (2019),
NGC 1052: Nakahara et al. (2020), NGC 315: Park et al. (2021), 4C 38.41: Algaba et al. (2019), 3C 264: Boccardi et al. (2019), 1H 0323+342: Hada et al. (2018),
and other sources: Kovalev et al. (2020). Note that we show two cases of different black hole masses for 1H 0323+342 (see Section 6.2).
42
Considering the empirical M–σd relation for an AGN with a typical black
hole mass (108−9
Me), we expect the temperature of the hot gas in the central
core to be ∼0.1–1 keV when the Bondi radius is close to the SGI radius.
13
The Astrophysical Journal, 940:65 (17pp), 2022 November 20 Okino et al.
14. The other two sources have a common property at the jet
base. They are surrounded by a dense obscuring disk/torus
causing free–free absorption (FFA). For NGC 1052, the phy-
sical size of the FFA torus is ∼0.5 pc (∼3.4 × 104
Rs) in radius
(Kameno et al. 2001), which is close to the deprojected break
location of ∼0.15 pc reported by Nakahara et al. (2020).43
For
NGC 4261, Haga et al. (2015) estimated the transition radius in
the accretion disk as ∼2 × 103
Rs from FFA measurements,
which is close to the break in the jet shape at ∼104
Rs for
NGC 4261 (Nakahara et al. 2018).
The break location of 1H 0323+342 is not well constrained
because of the significantly uncertain black hole mass. It shows
a distant collimation break for the lower black hole mass
(case B in Figure 12), while the jet collimation break occurs
near the SGI for the larger black hole mass (case A). Hada et al.
(2018) discussed that radiation-driven outflow/wind associated
with the narrow-line region may confine the jet of 1H 0323
+342 (case B), while 1H 0323+342 and M87 may share the
common jet collimation mechanism (case A), which is sup-
ported by 1H 0323+342 having a stationary recollimation
shock at the transitional region like the HST-1 knot in M87 (see
Doi et al. 2018).
Our results and Figure 12 indicate that the transition distance
of the jet shape is not necessarily determined by the SGI
boundary, but rather by its diverse environment, such as the
presence of the disk, torus, or disk wind and their spatial extent.
The hot gas cocoon surrounding the jet may also be an influ-
ence (e.g., Bromberg et al. 2011).
Recently, Boccardi et al. (2021) discussed the jet collimation
properties of various radio galaxies with respect to the activity
of the central accretion disk by categorizing samples into low-
and high-excitation radio galaxies (LERGs and HERGs). They
found that HERGs had larger radii and longer shape transition
distances for the collimation properties. For 3C 273, it is
unlikely that a component near the central engine, such as the
torus, is the critical factor causing the break because the col-
limation break in the 3C 273 jet is outside the range of
∼100 pc. Then 3C 273, if viewed from a typical viewing angle
of radio galaxies, would be categorized as a HERG given the
high ratio of the X-ray luminosity LX (2–10 keV) to the
Eddington luminosity LEdd implied by LX > 1.4 × 1046
erg s−1
(Cappi et al. 1998) and LEdd = 3.4 × 1046
erg s−1
given for
MBH = 2.6 × 108
Me (Gravity Collaboration et al. 2018).
Therefore, our results for 3C 273, which show relatively large
jet widths (2r 104
Rs at z 105
Rs) and a distant location of
the jet collimation break (zb > 106
Rs), are consistent with the
statistical trend reported in Boccardi et al. (2021).
Finally, we briefly note a scenario in which the jet colli-
mation break is governed by the internal jet physics proposed
by Kovalev et al. (2020). They proposed that under a single
ambient pressure profile, such as p ∝ z−2
, the collimation break
occurs in the region where the magnetic and particle energies
are equivalent. In their model, the break location depends
mainly on the initial magnetization parameters (σM) at the jet
base, as well as on the black hole mass and spin (see
Equation (7) in Nokhrina et al. 2020). The large σM for 3C 273
estimated in Nokhrina et al. (2015) may be qualitatively con-
sistent with the distant jet collimation break found in this study.
However, it is still hard to tightly constrain the value of σM, and
this is still an open problem. Therefore, it remains unclear
whether this scenario can explain the diverse distributions of
the break locations ranging from 104
Rs to 108
Rs shown in
Figure 12. If the value of σM can be estimated accurately for
more sources, the physical connection between σM and the
break location could be discussed in more detail.
7. Summary
In this paper, we have investigated the global jet structure of
the archetypical quasar 3C 273 with VLBA, HSA, and GMVA
observations. In particular, we have reported on new GMVA
observations at 86 GHz conducted in the first session involving
ALMA, which significantly enhance the sensitivity and angular
resolution of the images, providing the detailed morphology of
the innermost jet. With the robust imaging analysis using the
state-of-the-art RML imaging techniques, we obtained the jet
collimation profile over a wide range of 105
–108
Rs in depro-
jected distance. We summarize our results as follows.
1. The quasar 3C 273 jet is found to have the structural
transition from semiparabolic to conical/hyperbolic
shape at ∼107
Rs, providing the first clear example of a
quasar jet. Our results suggest the existence of the jet
collimation break for sources exhibiting widely different
accretion rates.
2. The collimation break is located in the area at ∼4 × 106
to 107
Rs where the jet shows a bending streamline
for ∼10 mas that persists for more than the typical jet
crossing time. The area is also known as the broadened
vertical structure with two brightening limbs resolved by
recent space-based VLBI observations. This peculiar and
persistent feature, co-located with the jet break, may be
explained by a stable magnetohydrodynamic feature, as
HST-1 may be for M87.
3. The extrapolation of the collimation profile is consistent
with the spatial distribution of BLRs and dusty winds
resolved with recent GRAVITY observations. Our
observations suggest that future higher-frequency obser-
vations, for instance with the Event Horizon Telescope at
230 and 345 GHz, can probe further inner regions where
the jet might interact with such hot dusty ionized gas.
4. Comparison of the collimation profile of the 3C 273 jet
with the velocity field obtained by long-term monitoring
observations at 15 and 43 GHz shows that the 3C 273 jet
is already accelerated to its apparent maximum velocity
upstream of the collimation break, which is apparently
different from the M87 jet, where the ends of the colli-
mation and acceleration zones are co-located.
5. The collimation break of 3C 273 is located several to ten
times further out than the estimated SGI location. Fur-
thermore, we compared all available locations of the jet
break from the literature with the SGI locations derived
from the MBH–σd relation, clearly showing that the
transition of the jet collimation is governed not only by
the SGI of the central black hole.
6. The relatively more distant location of the jet collimation
break discovered for 3C 273 seems broadly consistent
with the statistical trend of radio galaxies whereby
higher-excitation AGN sources tend to end their jet col-
limation at more distant locations from the central
black hole.
Our results demonstrate that ultrahigh-resolution observa-
tions with new millimeter facilities can provide many new
43
The break location is consistent with an independent measurement by
Kovalev et al. (2020) within a factor of ∼3.
14
The Astrophysical Journal, 940:65 (17pp), 2022 November 20 Okino et al.
15. insights into high-powered AGNs that were not previously
suitable for study of their jet collimation. Further study using
full polarimetric data and Faraday rotation synthesis can reveal
the distribution of the three-dimensional magnetic field and the
circumnuclear medium in the active collimation region (e.g.,
Park et al. 2019a). These explorations with polarimetric ana-
lysis using presented multifrequency data including GMVA
+ALMA will be presented in a forthcoming paper.
We thank the anonymous referee for many helpful and
constructive suggestions to improve this paper during the
review stage. This work was financially supported by grants
from the National Science Foundation (NSF; AST-1440254;
AST-1614868; AST-2034306) and the Japan Society for Pro-
motion of Science (JSPS; JP21H01137; JP20H01951;
JP19KK0081; JP18H03721.). This work has been partially
supported by the Generalitat Valenciana GenT Project CIDE-
GENT/2018/021 and by the MICINN Research Project
PID2019-108995GB-C22. This work was partially supported
by FAPESP (Fundação de Amparo à Pesquisa do Estado de
São Paulo) under grant 2021/01183-8. K. Akiyama is also
financially supported by the following NSF grants (AST-
1935980, AST-2107681, AST-2132700, OMA-2029670). A.C.
was supported by Hubble Fellowship grant HST-HF2-
51431.001-A awarded by the Space Telescope Science Insti-
tute, which is operated by the Association of Universities for
Research in Astronomy, Inc., for NASA, under contract NAS5-
26555. A.C. also gratefully acknowledges support from the
Princeton Gravity Initiative. S.I. is supported by NASA Hubble
Fellowship grant HST-HF2-51482.001-A awarded by the
Space Telescope Science Institute, which is operated by the
Association of Universities for Research in Astronomy, Inc.,
for NASA, under contract NAS5-26555. R.-S. L. is supported
by the Max Planck Partner Group of the MPG and the CAS and
acknowledges support by the Key Program of the National
Natural Science Foundation of China (grant No. 11933007),
the Key Research Program of Frontier Sciences, CAS (grant
No. ZDBS-LY-SLH011), and the Shanghai Pilot Program for
Basic Research—Chinese Academy of Science, Shanghai
Branch (JCYJ-SHFY-2022-013). Y.M. acknowledges the
support of the National Natural Science Foundation of China
(grant No. 12273022). The black hole Initiative at Harvard
University is financially supported by a grant from the John
Templeton Foundation. This paper makes use of the following
ALMA data: ADS/JAO.ALMA2016.1.01216.V. ALMA is a
partnership of ESO (representing its member states), NSF
(USA), and NINS (Japan), together with NRC (Canada),
MOST and ASIAA (Taiwan), and KASI (Republic of Korea),
in cooperation with the Republic of Chile. The Joint ALMA
Observatory is operated by ESO, AUI/NRAO and NAOJ. This
research has made use of data obtained with the Global Mil-
limeter VLBI Array (GMVA), which consists of telescopes
operated by the Max-Planck-Institut für Radioastronomie
(MPIfR), IRAM, Onsala, Metsahovi, Yebes, the Korean VLBI
Network, the Green Bank Observatory, and the Very Long
Baseline Array (VLBA). The VLBA is a facility of the
National Science Foundation operated under cooperative
agreement by Associated Universities, Inc. The National Radio
Astronomy Observatory is a facility of the National Science
Foundation operated under cooperative agreement by Asso-
ciated Universities, Inc. The data were correlated with the
DiFX correlator of the MPIfR in Bonn, Germany. This work is
partly based on observations with the 100 m telescope of the
MPIfR at Effelsberg. This work made use of the Swinburne
University of Technology software correlator (Deller et al.
2011), developed as part of the Australian Major National
Research Facilities Programme and operated under licence.
This research has made use of data from the MOJAVE database
that is maintained by the MOJAVE team (Lister et al. 2018).
This study makes use of 43 GHz VLBA data from the VLBA-
BU Blazar Monitoring Program (VLBA-BU-BLAZAR; http://
www.bu.edu/blazars/VLBAproject.html), funded by NASA
through the Fermi Guest Investigator Program.
Facilities: ALMA, VLBA, HSA, GMVA.
Software: SMILI (Akiyama et al. 2017a, 2017b), AIPS
(Greisen 2003), Difmap (Shepherd 1997), DiFX (Deller et al.
2007), astropy (Astropy Collaboration et al. 2013, 2018),
numpy (van der Walt et al. 2011), scipy (Virtanen et al. 2020),
matplotlib (Hunter 2007), pandas (McKinney 2010).
Appendix
Model Selection
We describe the model selection for our fitting analysis to the
jet radius profile presented in Section 5.5. To choose a better
model to explain the overall jet structure, we performed a fitting
analysis using single and broken power-law functions for entire
measurements except for the rapid increase in jet radii
around ∼107
Rs (see Section 5.5). Then we checked their
fractional deviations δ defined as
( )
d =
-
r r
r
. A1
model
model
For the case of a single power-law fit in Figure 13, the
deviations from the model are seen at both inner and outer
edges, while they are relatively small for a broken power-
law fit.
For more quantitative comparison, we computed the nor-
malized mean square error (NRMSE) values (e.g., Chael et al.
2016; Akiyama et al. 2017a, 2017b) for each model, defined as
( )
( )
=
S -
S
r r
r
NRMSE . A2
model
2
model
2
As shown in Figure 13, the resultant NRMSE value for the
broken power-law model is lower than that for the single
power-law model, also suggesting that the broken power-law
function is a better model for describing the whole range of
measured jet radii of 3C 273.
15
The Astrophysical Journal, 940:65 (17pp), 2022 November 20 Okino et al.
16. ORCID iDs
Hiroki Okino https:/
/orcid.org/0000-0003-3779-2016
Kazunori Akiyama https:/
/orcid.org/0000-0002-9475-4254
Keiichi Asada https:/
/orcid.org/0000-0001-6988-8763
José L. Gómez https:/
/orcid.org/0000-0003-4190-7613
Kazuhiro Hada https:/
/orcid.org/0000-0001-6906-772X
Mareki Honma https:/
/orcid.org/0000-0003-4058-9000
Thomas P. Krichbaum https:/
/orcid.org/0000-0002-
4892-9586
Motoki Kino https:/
/orcid.org/0000-0002-2709-7338
Hiroshi Nagai https:/
/orcid.org/0000-0003-0292-3645
Uwe Bach https:/
/orcid.org/0000-0002-7722-8412
Lindy Blackburn https:/
/orcid.org/0000-0002-9030-642X
Katherine L. Bouman https:/
/orcid.org/0000-0003-0077-4367
Andrew Chael https:/
/orcid.org/0000-0003-2966-6220
Geoffrey B. Crew https:/
/orcid.org/0000-0002-2079-3189
Sheperd S. Doeleman https:/
/orcid.org/0000-0002-
9031-0904
Vincent L. Fish https:/
/orcid.org/0000-0002-7128-9345
Ciriaco Goddi https:/
/orcid.org/0000-0002-2542-7743
Sara Issaoun https:/
/orcid.org/0000-0002-5297-921X
Michael D. Johnson https:/
/orcid.org/0000-0002-4120-3029
Svetlana Jorstad https:/
/orcid.org/0000-0001-6158-1708
Shoko Koyama https:/
/orcid.org/0000-0002-3723-3372
Colin J. Lonsdale https:/
/orcid.org/0000-0003-4062-4654
Ru-Sen Lu https:/
/orcid.org/0000-0002-7692-7967
Ivan Martí-Vidal https:/
/orcid.org/0000-0003-3708-9611
Lynn D. Matthews https:/
/orcid.org/0000-0002-3728-8082
Yosuke Mizuno https:/
/orcid.org/0000-0002-8131-6730
Kotaro Moriyama https:/
/orcid.org/0000-0003-1364-3761
Masanori Nakamura https:/
/orcid.org/0000-0001-
6081-2420
Hung-Yi Pu https:/
/orcid.org/0000-0001-9270-8812
Eduardo Ros https:/
/orcid.org/0000-0001-9503-4892
Tuomas Savolainen https:/
/orcid.org/0000-0001-6214-1085
Fumie Tazaki https:/
/orcid.org/0000-0003-0236-0600
Figure 13. Upper panel: radial profile of the jet in 3C 273 with different models of power-law functions. Measurement data are the same as in Figure 8. The gray
dashed line shows the best-fit single power-law function (r ∝ za
) with a = 0.80 obtained from all the data except for the gray shaded region. The red solid line shows
the best-fit broken power-law function as presented in Figure 8. Lower panel: fractional deviations of the jet radii from the obtained models. The red and gray squares
correspond to the deviations from the lines in the upper panel.
16
The Astrophysical Journal, 940:65 (17pp), 2022 November 20 Okino et al.
17. Jan Wagner https:/
/orcid.org/0000-0003-1105-6109
Maciek Wielgus https:/
/orcid.org/0000-0002-8635-4242
Anton Zensus https:/
/orcid.org/0000-0001-7470-3321
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