We studied the unique kinematic properties in massive filament G352.63-1.07 at 103 au spatial scale with the dense
molecular tracers observed with the Atacama Large Millimeter/submillimeter Array. We find the central massive
core M1 (12 Me) being separated from the surrounding filament with a velocity difference of
- =- - v vsys 2 km s 1 and a transverse separation within 3″. Meanwhile, as shown in multiple dense-gas
tracers, M1 has a spatial extension closely aligned with the main filament and is connected to the filament toward
both its ends. M1 thus represents a very beginning state for a massive, young star-forming core escaping from the
parental filament, within a timescale of ∼4000 yr. Based on its kinetic energy (3.5 × 1044 erg), the core escape is
unlikely solely due to the original filament motion or magnetic field but requires more energetic events such as a
rapid intense anisotropic collapse. The released energy also seems to noticeably increase the environmental
turbulence. This may help the filament to become stabilized again.
HST imaging of star-forming clumps in 6 GASP ram-pressure stripped galaxiesSérgio Sacani
Exploiting broad- and narrow-band images of the Hubble Space Telescope from near-UV to I-band
restframe, we study the star-forming clumps of six galaxies of the GASP sample undergoing strong
ram-pressure stripping (RPS). Clumps are detected in Hα and near-UV, tracing star formation on
different timescales. We consider clumps located in galaxy disks, in the stripped tails and those
formed in stripped gas but still close to the disk, called extraplanar. We detect 2406 Hα-selected
clumps (1708 in disks, 375 in extraplanar regions, and 323 in tails) and 3750 UV-selected clumps (2026
disk clumps, 825 extraplanar clumps and 899 tail clumps). Only ∼ 15% of star-forming clumps are
spatially resolved, meaning that most are smaller than ∼ 140 pc. We study the luminosity and size
distribution functions (LDFs and SDFs, respectively) and the luminosity-size relation. The average
LDF slope is 1.79 ± 0.09, while the average SDF slope is 3.1 ± 0.5. Results suggest the star formation
to be turbulence driven and scale-free, as in main-sequence galaxies. All the clumps, whether they are
in the disks or in the tails, have an enhanced Hα luminosity at a given size, compared to the clumps in
main-sequence galaxies. Indeed, their Hα luminosity is closer to that of clumps in starburst galaxies,
indicating that ram pressure is able to enhance the luminosity. No striking differences are found among
disk and tail clumps, suggesting that the different environments in which they are embedded play a
minor role in influencing the star formation.
HST imaging of star-forming clumps in 6 GASP ram-pressure stripped galaxiesSérgio Sacani
Exploiting broad- and narrow-band images of the Hubble Space Telescope from near-UV to I-band
restframe, we study the star-forming clumps of six galaxies of the GASP sample undergoing strong
ram-pressure stripping (RPS). Clumps are detected in Hα and near-UV, tracing star formation on
different timescales. We consider clumps located in galaxy disks, in the stripped tails and those
formed in stripped gas but still close to the disk, called extraplanar. We detect 2406 Hα-selected
clumps (1708 in disks, 375 in extraplanar regions, and 323 in tails) and 3750 UV-selected clumps (2026
disk clumps, 825 extraplanar clumps and 899 tail clumps). Only ∼ 15% of star-forming clumps are
spatially resolved, meaning that most are smaller than ∼ 140 pc. We study the luminosity and size
distribution functions (LDFs and SDFs, respectively) and the luminosity-size relation. The average
LDF slope is 1.79 ± 0.09, while the average SDF slope is 3.1 ± 0.5. Results suggest the star formation
to be turbulence driven and scale-free, as in main-sequence galaxies. All the clumps, whether they are
in the disks or in the tails, have an enhanced Hα luminosity at a given size, compared to the clumps in
main-sequence galaxies. Indeed, their Hα luminosity is closer to that of clumps in starburst galaxies,
indicating that ram pressure is able to enhance the luminosity. No striking differences are found among
disk and tail clumps, suggesting that the different environments in which they are embedded play a
minor role in influencing the star formation.
HST imaging of star-forming clumps in 6 GASP ram-pressure stripped galaxiesSérgio Sacani
Exploiting broad- and narrow-band images of the Hubble Space Telescope from near-UV to I-band
restframe, we study the star-forming clumps of six galaxies of the GASP sample undergoing strong
ram-pressure stripping (RPS). Clumps are detected in Hα and near-UV, tracing star formation on
different timescales. We consider clumps located in galaxy disks, in the stripped tails and those
formed in stripped gas but still close to the disk, called extraplanar. We detect 2406 Hα-selected
clumps (1708 in disks, 375 in extraplanar regions, and 323 in tails) and 3750 UV-selected clumps (2026
disk clumps, 825 extraplanar clumps and 899 tail clumps). Only ∼ 15% of star-forming clumps are
spatially resolved, meaning that most are smaller than ∼ 140 pc. We study the luminosity and size
distribution functions (LDFs and SDFs, respectively) and the luminosity-size relation. The average
LDF slope is 1.79 ± 0.09, while the average SDF slope is 3.1 ± 0.5. Results suggest the star formation
to be turbulence driven and scale-free, as in main-sequence galaxies. All the clumps, whether they are
in the disks or in the tails, have an enhanced Hα luminosity at a given size, compared to the clumps in
main-sequence galaxies. Indeed, their Hα luminosity is closer to that of clumps in starburst galaxies,
indicating that ram pressure is able to enhance the luminosity. No striking differences are found among
disk and tail clumps, suggesting that the different environments in which they are embedded play a
minor role in influencing the star formation.
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.
The SPHERE view of three interacting twin disc systems in polarised lightSérgio Sacani
Dense stellar environments as hosts of ongoing star formation increase the probability of gravitational encounters among stellar
systems during the early stages of evolution. Stellar interaction may occur through non-recurring, hyperbolic or parabolic passages
(a so-called ‘fly-by’), through secular binary evolution, or through binary capture. In all three scenarios, the strong gravitational
perturbation is expected to manifest itself in the disc structures around the individual stars. Here, we present near-infrared
polarised light observations that were taken with the SPHERE/IRDIS instrument of three known interacting twin-disc systems:
AS 205, EM* SR 24, and FU Orionis. The scattered light exposes spirals likely caused by the gravitational interaction. On
a larger scale, we observe connecting filaments between the stars. We analyse their very complex polarised intensity and put
particular attention to the presence of multiple light sources in these systems. The local angle of linear polarisation indicates
the source whose light dominates the scattering process from the bridging region between the two stars. Further, we show
that the polarised intensity from scattering with multiple relevant light sources results from an incoherent summation of the
individuals’ contribution. This can produce nulls of polarised intensity in an image, as potentially observed in AS 205.We discuss
the geometry and content of the systems by comparing the polarised light observations with other data at similar resolution,
namely with ALMA continuum and gas emission. Collective observational data can constrain the systems’ geometry and stellar
trajectories, with the important potential to differentiate between dynamical scenarios of stellar interaction.
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.
HST imaging of star-forming clumps in 6 GASP ram-pressure stripped galaxiesSérgio Sacani
Exploiting broad- and narrow-band images of the Hubble Space Telescope from near-UV to I-band
restframe, we study the star-forming clumps of six galaxies of the GASP sample undergoing strong
ram-pressure stripping (RPS). Clumps are detected in Hα and near-UV, tracing star formation on
different timescales. We consider clumps located in galaxy disks, in the stripped tails and those
formed in stripped gas but still close to the disk, called extraplanar. We detect 2406 Hα-selected
clumps (1708 in disks, 375 in extraplanar regions, and 323 in tails) and 3750 UV-selected clumps (2026
disk clumps, 825 extraplanar clumps and 899 tail clumps). Only ∼ 15% of star-forming clumps are
spatially resolved, meaning that most are smaller than ∼ 140 pc. We study the luminosity and size
distribution functions (LDFs and SDFs, respectively) and the luminosity-size relation. The average
LDF slope is 1.79 ± 0.09, while the average SDF slope is 3.1 ± 0.5. Results suggest the star formation
to be turbulence driven and scale-free, as in main-sequence galaxies. All the clumps, whether they are
in the disks or in the tails, have an enhanced Hα luminosity at a given size, compared to the clumps in
main-sequence galaxies. Indeed, their Hα luminosity is closer to that of clumps in starburst galaxies,
indicating that ram pressure is able to enhance the luminosity. No striking differences are found among
disk and tail clumps, suggesting that the different environments in which they are embedded play a
minor role in influencing the star formation.
HST imaging of star-forming clumps in 6 GASP ram-pressure stripped galaxiesSérgio Sacani
Exploiting broad- and narrow-band images of the Hubble Space Telescope from near-UV to I-band
restframe, we study the star-forming clumps of six galaxies of the GASP sample undergoing strong
ram-pressure stripping (RPS). Clumps are detected in Hα and near-UV, tracing star formation on
different timescales. We consider clumps located in galaxy disks, in the stripped tails and those
formed in stripped gas but still close to the disk, called extraplanar. We detect 2406 Hα-selected
clumps (1708 in disks, 375 in extraplanar regions, and 323 in tails) and 3750 UV-selected clumps (2026
disk clumps, 825 extraplanar clumps and 899 tail clumps). Only ∼ 15% of star-forming clumps are
spatially resolved, meaning that most are smaller than ∼ 140 pc. We study the luminosity and size
distribution functions (LDFs and SDFs, respectively) and the luminosity-size relation. The average
LDF slope is 1.79 ± 0.09, while the average SDF slope is 3.1 ± 0.5. Results suggest the star formation
to be turbulence driven and scale-free, as in main-sequence galaxies. All the clumps, whether they are
in the disks or in the tails, have an enhanced Hα luminosity at a given size, compared to the clumps in
main-sequence galaxies. Indeed, their Hα luminosity is closer to that of clumps in starburst galaxies,
indicating that ram pressure is able to enhance the luminosity. No striking differences are found among
disk and tail clumps, suggesting that the different environments in which they are embedded play a
minor role in influencing the star formation.
HST imaging of star-forming clumps in 6 GASP ram-pressure stripped galaxiesSérgio Sacani
Exploiting broad- and narrow-band images of the Hubble Space Telescope from near-UV to I-band
restframe, we study the star-forming clumps of six galaxies of the GASP sample undergoing strong
ram-pressure stripping (RPS). Clumps are detected in Hα and near-UV, tracing star formation on
different timescales. We consider clumps located in galaxy disks, in the stripped tails and those
formed in stripped gas but still close to the disk, called extraplanar. We detect 2406 Hα-selected
clumps (1708 in disks, 375 in extraplanar regions, and 323 in tails) and 3750 UV-selected clumps (2026
disk clumps, 825 extraplanar clumps and 899 tail clumps). Only ∼ 15% of star-forming clumps are
spatially resolved, meaning that most are smaller than ∼ 140 pc. We study the luminosity and size
distribution functions (LDFs and SDFs, respectively) and the luminosity-size relation. The average
LDF slope is 1.79 ± 0.09, while the average SDF slope is 3.1 ± 0.5. Results suggest the star formation
to be turbulence driven and scale-free, as in main-sequence galaxies. All the clumps, whether they are
in the disks or in the tails, have an enhanced Hα luminosity at a given size, compared to the clumps in
main-sequence galaxies. Indeed, their Hα luminosity is closer to that of clumps in starburst galaxies,
indicating that ram pressure is able to enhance the luminosity. No striking differences are found among
disk and tail clumps, suggesting that the different environments in which they are embedded play a
minor role in influencing the star formation.
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.
The SPHERE view of three interacting twin disc systems in polarised lightSérgio Sacani
Dense stellar environments as hosts of ongoing star formation increase the probability of gravitational encounters among stellar
systems during the early stages of evolution. Stellar interaction may occur through non-recurring, hyperbolic or parabolic passages
(a so-called ‘fly-by’), through secular binary evolution, or through binary capture. In all three scenarios, the strong gravitational
perturbation is expected to manifest itself in the disc structures around the individual stars. Here, we present near-infrared
polarised light observations that were taken with the SPHERE/IRDIS instrument of three known interacting twin-disc systems:
AS 205, EM* SR 24, and FU Orionis. The scattered light exposes spirals likely caused by the gravitational interaction. On
a larger scale, we observe connecting filaments between the stars. We analyse their very complex polarised intensity and put
particular attention to the presence of multiple light sources in these systems. The local angle of linear polarisation indicates
the source whose light dominates the scattering process from the bridging region between the two stars. Further, we show
that the polarised intensity from scattering with multiple relevant light sources results from an incoherent summation of the
individuals’ contribution. This can produce nulls of polarised intensity in an image, as potentially observed in AS 205.We discuss
the geometry and content of the systems by comparing the polarised light observations with other data at similar resolution,
namely with ALMA continuum and gas emission. Collective observational data can constrain the systems’ geometry and stellar
trajectories, with the important potential to differentiate between dynamical scenarios of stellar interaction.
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.
Triple Spiral Arms of a Triple Protostar System Imaged in Molecular LinesSérgio Sacani
Most stars form in multiple-star systems. For a better understanding of their formation processes, it is important to
resolve the individual protostellar components and the surrounding envelope and disk material at the earliest
possible formation epoch, because the formation history can be lost in a few orbital timescales. Here we present
Atacama Large Millimeter/submillimeter Array observational results of a young multiple protostellar system,
IRAS 04239+2436, where three well-developed large spiral arms were detected in the shocked SO emission.
Along the most conspicuous arm, the accretion streamer was also detected in the SO2 emission. The observational
results are complemented by numerical magnetohydrodynamic simulations, where those large arms only appear in
magnetically weakened clouds. Numerical simulations also suggest that the large triple spiral arms are the result of
gravitational interactions between compact triple protostars and the turbulent infalling envelope.
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.
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.
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.
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.
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.
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.
MUSE sneaks a peek at extreme ram-pressure stripping events. I. A kinematic s...Sérgio Sacani
- MUSE observations of the galaxy ESO137-001 reveal an extended gaseous tail over 30 kpc long traced by H-alpha emission, providing evidence of an extreme ram pressure stripping event as the galaxy falls into the massive Norma galaxy cluster.
- Analysis of the H-alpha kinematics and stellar velocity field show that ram pressure has removed the interstellar medium from the outer disk while the primary tail is still fed by gas from the galaxy center, with gravitational interactions not appearing to be the main mechanism of gas removal.
- The stripped gas retains evidence of the disk's rotational velocity out to around 20 kpc downstream, indicating the galaxy is moving radially along the plane of the sky, while
This document describes observations of the galaxy ESO137-001 using the MUSE instrument on the VLT. The key points are:
1) MUSE observations reveal an extended gas tail stretching over 30 kpc from the galaxy, tracing ongoing ram pressure stripping as it falls into the Norma galaxy cluster.
2) Analysis of the gas kinematics and stellar velocity field show that ram pressure has removed the interstellar medium from the outer disk while the primary tail is still fed by gas from the galaxy center.
3) The stripped gas retains evidence of the disk's rotational velocity out to 20 kpc downstream, indicating the galaxy is moving radially through the cluster. Beyond this the gas shows greater turbulence,
Kinematics and simulations_of_the_stellar_stream_in_the_halo_of_the_umbrella_...Sérgio Sacani
This document summarizes a study of the stellar stream and substructures around the Umbrella Galaxy (NGC 4651). Deep imaging and spectroscopy were used to characterize the properties and kinematics of the stream. Tracer objects like globular clusters and planetary nebulae were identified and found to delineate a kinematically cold feature in position-velocity space. Dynamical modeling suggests the stream originated from the tidal disruption of a dwarf galaxy on a highly eccentric orbit about 6-10 billion years ago. This work demonstrates the feasibility of using discrete tracers to recover the kinematics and model the dynamics of low surface brightness stellar streams around distant galaxies.
EXTINCTION AND THE DIMMING OF KIC 8462852Sérgio Sacani
To test alternative hypotheses for the behavior of KIC 8462852, we obtained measurements of the star
over a wide wavelength range from the UV to the mid-infrared from October 2015 through December
2016, using Swift, Spitzer and at AstroLAB IRIS. The star faded in a manner similar to the longterm
fading seen in Kepler data about 1400 days previously. The dimming rate for the entire period
reported is 22.1 ± 9.7 milli-mag yr−1
in the Swift wavebands, with amounts of 21.0 ± 4.5 mmag in
the groundbased B measurements, 14.0 ± 4.5 mmag in V , and 13.0 ± 4.5 in R, and a rate of 5.0 ± 1.2
mmag yr−1 averaged over the two warm Spitzer bands. Although the dimming is small, it is seen at
& 3 σ by three different observatories operating from the UV to the IR. The presence of long-term
secular dimming means that previous SED models of the star based on photometric measurements
taken years apart may not be accurate. We find that stellar models with Tef f = 7000 - 7100 K and
AV ∼ 0.73 best fit the Swift data from UV to optical. These models also show no excess in the
near-simultaneous Spitzer photometry at 3.6 and 4.5 µm, although a longer wavelength excess from
a substantial debris disk is still possible (e.g., as around Fomalhaut). The wavelength dependence of
the fading favors a relatively neutral color (i.e., RV & 5, but not flat across all the bands) compared
with the extinction law for the general ISM (RV = 3.1), suggesting that the dimming arises from
circumstellar material
A giant thin stellar stream in the Coma Galaxy ClusterSérgio Sacani
The study of dynamically cold stellar streams reveals information about the gravitational potential where they reside and provides
important constraints on the properties of dark matter. However, the intrinsic faintness of these streams makes their detection beyond
Local environments highly challenging. Here, we report the detection of an extremely faint stellar stream (µg,max = 29.5 mag arcsec−2
)
with an extraordinarily coherent and thin morphology in the Coma Galaxy Cluster. This Giant Coma Stream spans ∼510 kpc in length
and appears as a free-floating structure located at a projected distance of 0.8 Mpc from the center of Coma. We do not identify any
potential galaxy remnant or core, and the stream structure appears featureless in our data. We interpret the Giant Coma Stream as
being a recently accreted, tidally disrupting passive dwarf. Using the Illustris-TNG50 simulation, we identify a case with similar
characteristics, showing that, although rare, these types of streams are predicted to exist in Λ-CDM. Our work unveils the presence
of free-floating, extremely faint and thin stellar streams in galaxy clusters, widening the environmental context in which these objects
are found ahead of their promising future application in the study of the properties of dark matter.
AT2023fhn (the Finch): a Luminous Fast Blue Optical Transient at a large offs...Sérgio Sacani
Luminous Fast Blue Optical Transients (LFBOTs) - the prototypical example being AT 2018cow - are a rare class of events
whose origins are poorly understood. They are characterised by rapid evolution, featureless blue spectra at early times, and
luminous X-ray and radio emission. LFBOTs thus far have been found exclusively at small projected offsets from star-forming
host galaxies. We present Hubble Space Telescope, Gemini, Chandra and Very Large Array observations of a new LFBOT,
AT 2023fhn. The Hubble Space Telescope data reveal a large offset (> 3.5 half-light radii) from the two closest galaxies, both
at redshift 𝑧 ∼ 0.24. The location of AT 2023fhn is in stark contrast with previous events, and demonstrates that LFBOTs can
occur in a range of galactic environments.
The massive relic galaxy NGC 1277 is dark matter deficient From dynamical mod...Sérgio Sacani
According to the Λ cold dark matter (ΛCDM) cosmology, present-day galaxies with stellar masses M? > 1011 M should contain
a sizable fraction of dark matter within their stellar body. Models indicate that in massive early-type galaxies (ETGs) with M? ≈
1.5 × 1011 M, dark matter should account for ∼15% of the dynamical mass within one effective radius (1 Re) and for ∼60% within
5 Re
. Most massive ETGs have been shaped through a two-phase process: the rapid growth of a compact core was followed by the
accretion of an extended envelope through mergers. The exceedingly rare galaxies that have avoided the second phase, the so-called
relic galaxies, are thought to be the frozen remains of the massive ETG population at z & 2. The best relic galaxy candidate discovered
to date is NGC 1277, in the Perseus cluster. We used deep integral field George and Cynthia Mitchel Spectrograph (GCMS) data to
revisit NGC 1277 out to an unprecedented radius of 6 kpc (corresponding to 5 Re). By using Jeans anisotropic modelling, we find
a negligible dark matter fraction within 5 Re (fDM(5 Re) < 0.05; two-sigma confidence level), which is in tension with the ΛCDM
expectation. Since the lack of an extended envelope would reduce dynamical friction and prevent the accretion of an envelope, we
propose that NGC 1277 lost its dark matter very early or that it was dark matter deficient ab initio. We discuss our discovery in the
framework of recent proposals, suggesting that some relic galaxies may result from dark matter stripping as they fell in and interacted
within galaxy clusters. Alternatively, NGC 1277 might have been born in a high-velocity collision of gas-rich proto-galactic fragments,
where dark matter left behind a disc of dissipative baryons. We speculate that the relative velocities of ≈2000 km s−1
required for the
latter process to happen were possible in the progenitors of the present-day rich galaxy clusters.
We present the 2020 version of the Siena Galaxy Atlas (SGA-2020), a multiwavelength optical and infrared
imaging atlas of 383,620 nearby galaxies. The SGA-2020 uses optical grz imaging over ≈20,000 deg2 from the
Dark Energy Spectroscopic Instrument (DESI) Legacy Imaging Surveys Data Release 9 and infrared imaging in
four bands (spanning 3.4–22 μm) from the 6 year unWISE coadds; it is more than 95% complete for galaxies larger
than R(26) ≈ 25″ and r < 18 measured at the 26 mag arcsec−2 isophote in the r band. The atlas delivers precise
coordinates, multiwavelength mosaics, azimuthally averaged optical surface-brightness profiles, model images and
photometry, and additional ancillary metadata for the full sample. Coupled with existing and forthcoming optical
spectroscopy from the DESI, the SGA-2020 will facilitate new detailed studies of the star formation and mass
assembly histories of nearby galaxies; enable precise measurements of the local velocity field via the Tully–Fisher
and fundamental plane relations; serve as a reference sample of lasting legacy value for time-domain and
multimessenger astronomical events; and more.
Quasiperiodic Variations of Coronal Mass Ejections with Different Angular WidthsSérgio Sacani
Coronal mass ejections (CMEs) are energetic expulsions of organized magnetic features from the Sun. The study of
CME quasiperiodicity helps establish a possible relationship between CMEs, solar flares, and geomagnetic
disturbances. We used the angular width of CMEs as a criterion for classifying the CMEs in the study. Based on 25
yr of observational data, we systematically analyzed the quasiperiodic variations corresponding to the CME
occurrence rate of different angular widths in the northern and southern hemispheres, using frequency and time–
frequency analysis methods. There are various periods for CMEs of different angular widths: 9 months, 1.7 yr, and
3.3–4.3 yr. Compared with previous studies based on the occurrence rate of CMEs, we obtained the same periods
of 1.2 (±0.01), 3.1 (±0.04), and ≈6.1 (±0.4) months, and 1.2 (±0.1) and 2.4 (±0.4) yr. We also found additional
periods of all CMEs that appear only in one hemisphere or during a specific solar cycle. For example, 7.1 (±0.2)
months and 4.1 (±0.2) yr in the northern hemisphere, 1 (±0.004) and 5.9 (±0.2) months and 1 (±0.1), 1.4 (±0.1),
and 2.4 (±0.4) yr in the southern hemisphere, 6.1 (±0.4) months in solar cycle 23, and 6.1 (±0.4) months and 1.2
(±0.1) and 3.7 (±0.2) yr in solar cycle 24. The analysis shows that quasiperiodic variations of the CMEs are a link
among oscillations in coronal magnetic activity, solar flare eruptions, and interplanetary space
GRMHD Simulations of Neutron-star Mergers with Weak Interactions: r-process N...Sérgio Sacani
Fast neutron-rich material ejected dynamically over 10 ms during the merger of a binary neutron star (BNS) can
give rise to distinctive electromagnetic counterparts to the system’s gravitational-wave emission that serve as a
“smoking gun” to distinguish between a BNS and an NS–black hole merger. We present novel ab initio modeling
of the kilonova precursor and kilonova afterglow based on 3D general-relativistic magnetohydrodynamic
simulations of BNS mergers with nuclear, tabulated, finite-temperature equations of state (EOSs), weak
interactions, and approximate neutrino transport. We analyze dynamical mass ejection from 1.35–1.35 Me
binaries, consistent with properties of the first observed BNS merger GW170817, using three nuclear EOSs that
span the range of allowed compactness of 1.35 Me-neutron stars. Nuclear reaction network calculations yield a
robust second-to-third-peak r-process. We find few ×10−6 Me of fast (v > 0.6c) ejecta that give rise to broadband
synchrotron emission on ∼years timescales, consistent with tentative evidence for excess X-ray/radio emission
following GW170817. We find ≈2 × 10−5 Me of free neutrons that power a kilonova precursor on hours
timescale. A boost in early UV/optical brightness by a factor of a few due to previously neglected relativistic
effects, with enhancements up to 10 hr post-merger, is promising for future detection with UV/optical telescopes
like Swift or ULTRASAT. We find that a recently predicted opacity boost due to highly ionized lanthanides at
70,000 K is unlikely to affect the early kilonova based on the obtained ejecta structures. Azimuthal
inhomogeneities in dynamical ejecta composition for soft EOSs found here (“lanthanide/actinide pockets”) may
have observable consequences for both early kilonova and late-time nebular emission.
The physical conditions_in_a_pre_super_star_cluster_molecular_cloud_in_the_an...Sérgio Sacani
The document summarizes a study of an extreme molecular cloud in the Antennae galaxies that has properties consistent with forming a globular cluster. ALMA observations reveal a cloud with a radius of 24 pc and mass greater than 5 million solar masses. While capable of forming a globular cluster, a lack of associated thermal radio emission indicates star formation has not yet begun to alter the environment, suggesting the cloud is in an early stage of evolution. For the cloud to be confined as observed, an external pressure over 10,000 times greater than typical interstellar pressure is required, supporting the theory that high pressures are needed to form globular clusters in extreme environments like mergers.
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.
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
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
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Triple Spiral Arms of a Triple Protostar System Imaged in Molecular LinesSérgio Sacani
Most stars form in multiple-star systems. For a better understanding of their formation processes, it is important to
resolve the individual protostellar components and the surrounding envelope and disk material at the earliest
possible formation epoch, because the formation history can be lost in a few orbital timescales. Here we present
Atacama Large Millimeter/submillimeter Array observational results of a young multiple protostellar system,
IRAS 04239+2436, where three well-developed large spiral arms were detected in the shocked SO emission.
Along the most conspicuous arm, the accretion streamer was also detected in the SO2 emission. The observational
results are complemented by numerical magnetohydrodynamic simulations, where those large arms only appear in
magnetically weakened clouds. Numerical simulations also suggest that the large triple spiral arms are the result of
gravitational interactions between compact triple protostars and the turbulent infalling envelope.
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.
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.
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.
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.
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.
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.
MUSE sneaks a peek at extreme ram-pressure stripping events. I. A kinematic s...Sérgio Sacani
- MUSE observations of the galaxy ESO137-001 reveal an extended gaseous tail over 30 kpc long traced by H-alpha emission, providing evidence of an extreme ram pressure stripping event as the galaxy falls into the massive Norma galaxy cluster.
- Analysis of the H-alpha kinematics and stellar velocity field show that ram pressure has removed the interstellar medium from the outer disk while the primary tail is still fed by gas from the galaxy center, with gravitational interactions not appearing to be the main mechanism of gas removal.
- The stripped gas retains evidence of the disk's rotational velocity out to around 20 kpc downstream, indicating the galaxy is moving radially along the plane of the sky, while
This document describes observations of the galaxy ESO137-001 using the MUSE instrument on the VLT. The key points are:
1) MUSE observations reveal an extended gas tail stretching over 30 kpc from the galaxy, tracing ongoing ram pressure stripping as it falls into the Norma galaxy cluster.
2) Analysis of the gas kinematics and stellar velocity field show that ram pressure has removed the interstellar medium from the outer disk while the primary tail is still fed by gas from the galaxy center.
3) The stripped gas retains evidence of the disk's rotational velocity out to 20 kpc downstream, indicating the galaxy is moving radially through the cluster. Beyond this the gas shows greater turbulence,
Kinematics and simulations_of_the_stellar_stream_in_the_halo_of_the_umbrella_...Sérgio Sacani
This document summarizes a study of the stellar stream and substructures around the Umbrella Galaxy (NGC 4651). Deep imaging and spectroscopy were used to characterize the properties and kinematics of the stream. Tracer objects like globular clusters and planetary nebulae were identified and found to delineate a kinematically cold feature in position-velocity space. Dynamical modeling suggests the stream originated from the tidal disruption of a dwarf galaxy on a highly eccentric orbit about 6-10 billion years ago. This work demonstrates the feasibility of using discrete tracers to recover the kinematics and model the dynamics of low surface brightness stellar streams around distant galaxies.
EXTINCTION AND THE DIMMING OF KIC 8462852Sérgio Sacani
To test alternative hypotheses for the behavior of KIC 8462852, we obtained measurements of the star
over a wide wavelength range from the UV to the mid-infrared from October 2015 through December
2016, using Swift, Spitzer and at AstroLAB IRIS. The star faded in a manner similar to the longterm
fading seen in Kepler data about 1400 days previously. The dimming rate for the entire period
reported is 22.1 ± 9.7 milli-mag yr−1
in the Swift wavebands, with amounts of 21.0 ± 4.5 mmag in
the groundbased B measurements, 14.0 ± 4.5 mmag in V , and 13.0 ± 4.5 in R, and a rate of 5.0 ± 1.2
mmag yr−1 averaged over the two warm Spitzer bands. Although the dimming is small, it is seen at
& 3 σ by three different observatories operating from the UV to the IR. The presence of long-term
secular dimming means that previous SED models of the star based on photometric measurements
taken years apart may not be accurate. We find that stellar models with Tef f = 7000 - 7100 K and
AV ∼ 0.73 best fit the Swift data from UV to optical. These models also show no excess in the
near-simultaneous Spitzer photometry at 3.6 and 4.5 µm, although a longer wavelength excess from
a substantial debris disk is still possible (e.g., as around Fomalhaut). The wavelength dependence of
the fading favors a relatively neutral color (i.e., RV & 5, but not flat across all the bands) compared
with the extinction law for the general ISM (RV = 3.1), suggesting that the dimming arises from
circumstellar material
A giant thin stellar stream in the Coma Galaxy ClusterSérgio Sacani
The study of dynamically cold stellar streams reveals information about the gravitational potential where they reside and provides
important constraints on the properties of dark matter. However, the intrinsic faintness of these streams makes their detection beyond
Local environments highly challenging. Here, we report the detection of an extremely faint stellar stream (µg,max = 29.5 mag arcsec−2
)
with an extraordinarily coherent and thin morphology in the Coma Galaxy Cluster. This Giant Coma Stream spans ∼510 kpc in length
and appears as a free-floating structure located at a projected distance of 0.8 Mpc from the center of Coma. We do not identify any
potential galaxy remnant or core, and the stream structure appears featureless in our data. We interpret the Giant Coma Stream as
being a recently accreted, tidally disrupting passive dwarf. Using the Illustris-TNG50 simulation, we identify a case with similar
characteristics, showing that, although rare, these types of streams are predicted to exist in Λ-CDM. Our work unveils the presence
of free-floating, extremely faint and thin stellar streams in galaxy clusters, widening the environmental context in which these objects
are found ahead of their promising future application in the study of the properties of dark matter.
AT2023fhn (the Finch): a Luminous Fast Blue Optical Transient at a large offs...Sérgio Sacani
Luminous Fast Blue Optical Transients (LFBOTs) - the prototypical example being AT 2018cow - are a rare class of events
whose origins are poorly understood. They are characterised by rapid evolution, featureless blue spectra at early times, and
luminous X-ray and radio emission. LFBOTs thus far have been found exclusively at small projected offsets from star-forming
host galaxies. We present Hubble Space Telescope, Gemini, Chandra and Very Large Array observations of a new LFBOT,
AT 2023fhn. The Hubble Space Telescope data reveal a large offset (> 3.5 half-light radii) from the two closest galaxies, both
at redshift 𝑧 ∼ 0.24. The location of AT 2023fhn is in stark contrast with previous events, and demonstrates that LFBOTs can
occur in a range of galactic environments.
The massive relic galaxy NGC 1277 is dark matter deficient From dynamical mod...Sérgio Sacani
According to the Λ cold dark matter (ΛCDM) cosmology, present-day galaxies with stellar masses M? > 1011 M should contain
a sizable fraction of dark matter within their stellar body. Models indicate that in massive early-type galaxies (ETGs) with M? ≈
1.5 × 1011 M, dark matter should account for ∼15% of the dynamical mass within one effective radius (1 Re) and for ∼60% within
5 Re
. Most massive ETGs have been shaped through a two-phase process: the rapid growth of a compact core was followed by the
accretion of an extended envelope through mergers. The exceedingly rare galaxies that have avoided the second phase, the so-called
relic galaxies, are thought to be the frozen remains of the massive ETG population at z & 2. The best relic galaxy candidate discovered
to date is NGC 1277, in the Perseus cluster. We used deep integral field George and Cynthia Mitchel Spectrograph (GCMS) data to
revisit NGC 1277 out to an unprecedented radius of 6 kpc (corresponding to 5 Re). By using Jeans anisotropic modelling, we find
a negligible dark matter fraction within 5 Re (fDM(5 Re) < 0.05; two-sigma confidence level), which is in tension with the ΛCDM
expectation. Since the lack of an extended envelope would reduce dynamical friction and prevent the accretion of an envelope, we
propose that NGC 1277 lost its dark matter very early or that it was dark matter deficient ab initio. We discuss our discovery in the
framework of recent proposals, suggesting that some relic galaxies may result from dark matter stripping as they fell in and interacted
within galaxy clusters. Alternatively, NGC 1277 might have been born in a high-velocity collision of gas-rich proto-galactic fragments,
where dark matter left behind a disc of dissipative baryons. We speculate that the relative velocities of ≈2000 km s−1
required for the
latter process to happen were possible in the progenitors of the present-day rich galaxy clusters.
We present the 2020 version of the Siena Galaxy Atlas (SGA-2020), a multiwavelength optical and infrared
imaging atlas of 383,620 nearby galaxies. The SGA-2020 uses optical grz imaging over ≈20,000 deg2 from the
Dark Energy Spectroscopic Instrument (DESI) Legacy Imaging Surveys Data Release 9 and infrared imaging in
four bands (spanning 3.4–22 μm) from the 6 year unWISE coadds; it is more than 95% complete for galaxies larger
than R(26) ≈ 25″ and r < 18 measured at the 26 mag arcsec−2 isophote in the r band. The atlas delivers precise
coordinates, multiwavelength mosaics, azimuthally averaged optical surface-brightness profiles, model images and
photometry, and additional ancillary metadata for the full sample. Coupled with existing and forthcoming optical
spectroscopy from the DESI, the SGA-2020 will facilitate new detailed studies of the star formation and mass
assembly histories of nearby galaxies; enable precise measurements of the local velocity field via the Tully–Fisher
and fundamental plane relations; serve as a reference sample of lasting legacy value for time-domain and
multimessenger astronomical events; and more.
Quasiperiodic Variations of Coronal Mass Ejections with Different Angular WidthsSérgio Sacani
Coronal mass ejections (CMEs) are energetic expulsions of organized magnetic features from the Sun. The study of
CME quasiperiodicity helps establish a possible relationship between CMEs, solar flares, and geomagnetic
disturbances. We used the angular width of CMEs as a criterion for classifying the CMEs in the study. Based on 25
yr of observational data, we systematically analyzed the quasiperiodic variations corresponding to the CME
occurrence rate of different angular widths in the northern and southern hemispheres, using frequency and time–
frequency analysis methods. There are various periods for CMEs of different angular widths: 9 months, 1.7 yr, and
3.3–4.3 yr. Compared with previous studies based on the occurrence rate of CMEs, we obtained the same periods
of 1.2 (±0.01), 3.1 (±0.04), and ≈6.1 (±0.4) months, and 1.2 (±0.1) and 2.4 (±0.4) yr. We also found additional
periods of all CMEs that appear only in one hemisphere or during a specific solar cycle. For example, 7.1 (±0.2)
months and 4.1 (±0.2) yr in the northern hemisphere, 1 (±0.004) and 5.9 (±0.2) months and 1 (±0.1), 1.4 (±0.1),
and 2.4 (±0.4) yr in the southern hemisphere, 6.1 (±0.4) months in solar cycle 23, and 6.1 (±0.4) months and 1.2
(±0.1) and 3.7 (±0.2) yr in solar cycle 24. The analysis shows that quasiperiodic variations of the CMEs are a link
among oscillations in coronal magnetic activity, solar flare eruptions, and interplanetary space
GRMHD Simulations of Neutron-star Mergers with Weak Interactions: r-process N...Sérgio Sacani
Fast neutron-rich material ejected dynamically over 10 ms during the merger of a binary neutron star (BNS) can
give rise to distinctive electromagnetic counterparts to the system’s gravitational-wave emission that serve as a
“smoking gun” to distinguish between a BNS and an NS–black hole merger. We present novel ab initio modeling
of the kilonova precursor and kilonova afterglow based on 3D general-relativistic magnetohydrodynamic
simulations of BNS mergers with nuclear, tabulated, finite-temperature equations of state (EOSs), weak
interactions, and approximate neutrino transport. We analyze dynamical mass ejection from 1.35–1.35 Me
binaries, consistent with properties of the first observed BNS merger GW170817, using three nuclear EOSs that
span the range of allowed compactness of 1.35 Me-neutron stars. Nuclear reaction network calculations yield a
robust second-to-third-peak r-process. We find few ×10−6 Me of fast (v > 0.6c) ejecta that give rise to broadband
synchrotron emission on ∼years timescales, consistent with tentative evidence for excess X-ray/radio emission
following GW170817. We find ≈2 × 10−5 Me of free neutrons that power a kilonova precursor on hours
timescale. A boost in early UV/optical brightness by a factor of a few due to previously neglected relativistic
effects, with enhancements up to 10 hr post-merger, is promising for future detection with UV/optical telescopes
like Swift or ULTRASAT. We find that a recently predicted opacity boost due to highly ionized lanthanides at
70,000 K is unlikely to affect the early kilonova based on the obtained ejecta structures. Azimuthal
inhomogeneities in dynamical ejecta composition for soft EOSs found here (“lanthanide/actinide pockets”) may
have observable consequences for both early kilonova and late-time nebular emission.
The physical conditions_in_a_pre_super_star_cluster_molecular_cloud_in_the_an...Sérgio Sacani
The document summarizes a study of an extreme molecular cloud in the Antennae galaxies that has properties consistent with forming a globular cluster. ALMA observations reveal a cloud with a radius of 24 pc and mass greater than 5 million solar masses. While capable of forming a globular cluster, a lack of associated thermal radio emission indicates star formation has not yet begun to alter the environment, suggesting the cloud is in an early stage of evolution. For the cloud to be confined as observed, an external pressure over 10,000 times greater than typical interstellar pressure is required, supporting the theory that high pressures are needed to form globular clusters in extreme environments like mergers.
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.
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
Similar to A High-mass, Young Star-forming Core Escaping from Its Parental Filament (20)
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.
Constraints on Neutrino Natal Kicks from Black-Hole Binary VFTS 243Sérgio Sacani
The recently reported observation of VFTS 243 is the first example of a massive black-hole binary
system with negligible binary interaction following black-hole formation. The black-hole mass (≈10M⊙)
and near-circular orbit (e ≈ 0.02) of VFTS 243 suggest that the progenitor star experienced complete
collapse, with energy-momentum being lost predominantly through neutrinos. VFTS 243 enables us to
constrain the natal kick and neutrino-emission asymmetry during black-hole formation. At 68% confidence
level, the natal kick velocity (mass decrement) is ≲10 km=s (≲1.0M⊙), with a full probability distribution
that peaks when ≈0.3M⊙ were ejected, presumably in neutrinos, and the black hole experienced a natal
kick of 4 km=s. The neutrino-emission asymmetry is ≲4%, with best fit values of ∼0–0.2%. Such a small
neutrino natal kick accompanying black-hole formation is in agreement with theoretical predictions.
Detectability of Solar Panels as a TechnosignatureSérgio Sacani
In this work, we assess the potential detectability of solar panels made of silicon on an Earth-like
exoplanet as a potential technosignature. Silicon-based photovoltaic cells have high reflectance in the
UV-VIS and in the near-IR, within the wavelength range of a space-based flagship mission concept
like the Habitable Worlds Observatory (HWO). Assuming that only solar energy is used to provide
the 2022 human energy needs with a land cover of ∼ 2.4%, and projecting the future energy demand
assuming various growth-rate scenarios, we assess the detectability with an 8 m HWO-like telescope.
Assuming the most favorable viewing orientation, and focusing on the strong absorption edge in the
ultraviolet-to-visible (0.34 − 0.52 µm), we find that several 100s of hours of observation time is needed
to reach a SNR of 5 for an Earth-like planet around a Sun-like star at 10pc, even with a solar panel
coverage of ∼ 23% land coverage of a future Earth. We discuss the necessity of concepts like Kardeshev
Type I/II civilizations and Dyson spheres, which would aim to harness vast amounts of energy. Even
with much larger populations than today, the total energy use of human civilization would be orders of
magnitude below the threshold for causing direct thermal heating or reaching the scale of a Kardashev
Type I civilization. Any extraterrrestrial civilization that likewise achieves sustainable population
levels may also find a limit on its need to expand, which suggests that a galaxy-spanning civilization
as imagined in the Fermi paradox may not exist.
The solar dynamo begins near the surfaceSérgio Sacani
The magnetic dynamo cycle of the Sun features a distinct pattern: a propagating
region of sunspot emergence appears around 30° latitude and vanishes near the
equator every 11 years (ref. 1). Moreover, longitudinal flows called torsional oscillations
closely shadow sunspot migration, undoubtedly sharing a common cause2. Contrary
to theories suggesting deep origins of these phenomena, helioseismology pinpoints
low-latitude torsional oscillations to the outer 5–10% of the Sun, the near-surface
shear layer3,4. Within this zone, inwardly increasing differential rotation coupled with
a poloidal magnetic field strongly implicates the magneto-rotational instability5,6,
prominent in accretion-disk theory and observed in laboratory experiments7.
Together, these two facts prompt the general question: whether the solar dynamo is
possibly a near-surface instability. Here we report strong affirmative evidence in stark
contrast to traditional models8 focusing on the deeper tachocline. Simple analytic
estimates show that the near-surface magneto-rotational instability better explains
the spatiotemporal scales of the torsional oscillations and inferred subsurface
magnetic field amplitudes9. State-of-the-art numerical simulations corroborate these
estimates and reproduce hemispherical magnetic current helicity laws10. The dynamo
resulting from a well-understood near-surface phenomenon improves prospects
for accurate predictions of full magnetic cycles and space weather, affecting the
electromagnetic infrastructure of Earth.
Extensive Pollution of Uranus and Neptune’s Atmospheres by Upsweep of Icy Mat...Sérgio Sacani
In the Nice model of solar system formation, Uranus and Neptune undergo an orbital upheaval,
sweeping through a planetesimal disk. The region of the disk from which material is accreted by
the ice giants during this phase of their evolution has not previously been identified. We perform
direct N-body orbital simulations of the four giant planets to determine the amount and origin of solid
accretion during this orbital upheaval. We find that the ice giants undergo an extreme bombardment
event, with collision rates as much as ∼3 per hour assuming km-sized planetesimals, increasing the
total planet mass by up to ∼0.35%. In all cases, the initially outermost ice giant experiences the
largest total enhancement. We determine that for some plausible planetesimal properties, the resulting
atmospheric enrichment could potentially produce sufficient latent heat to alter the planetary cooling
timescale according to existing models. Our findings suggest that substantial accretion during this
phase of planetary evolution may have been sufficient to impact the atmospheric composition and
thermal evolution of the ice giants, motivating future work on the fate of deposited solid material.
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.
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Authoring a personal GPT for your research and practice: How we created the Q...Leonel Morgado
Thematic analysis in qualitative research is a time-consuming and systematic task, typically done using teams. Team members must ground their activities on common understandings of the major concepts underlying the thematic analysis, and define criteria for its development. However, conceptual misunderstandings, equivocations, and lack of adherence to criteria are challenges to the quality and speed of this process. Given the distributed and uncertain nature of this process, we wondered if the tasks in thematic analysis could be supported by readily available artificial intelligence chatbots. Our early efforts point to potential benefits: not just saving time in the coding process but better adherence to criteria and grounding, by increasing triangulation between humans and artificial intelligence. This tutorial will provide a description and demonstration of the process we followed, as two academic researchers, to develop a custom ChatGPT to assist with qualitative coding in the thematic data analysis process of immersive learning accounts in a survey of the academic literature: QUAL-E Immersive Learning Thematic Analysis Helper. In the hands-on time, participants will try out QUAL-E and develop their ideas for their own qualitative coding ChatGPT. Participants that have the paid ChatGPT Plus subscription can create a draft of their assistants. The organizers will provide course materials and slide deck that participants will be able to utilize to continue development of their custom GPT. The paid subscription to ChatGPT Plus is not required to participate in this workshop, just for trying out personal GPTs during it.
2. directions, eventually forming a broadened stellar distribution
in parallel with the filament. But in all these studies, the young
stars are either totally separated from the filaments or have
dissipated the surrounding gas (e.g., Jerabkova et al. 2019;
Gupta & Chen 2022). So we still need to investigate the initial
dynamical condition when young stellar objects (YSOs)are
leaving their parental structures.
G352.63-1.07 is a massive, young star-forming region at a
precisely measured distance of D = 690 pc (Chen et al. 2021,
hereafter Chen21). It contains several massive cores aligned on
a dense filament. As shown in Chen21, the filament has
actively ongoing dynamical features, including prominent
outflows and mass transfer flows, which induced bright shock
emissions. However, due to the limited molecular tracers and
sensitivities, the gas motion among the cores and filaments is
still undetermined. In this work, we explored the gas motion
using optically thin lines, which demonstrate the unique
tendency of the escaping massive core M1. The observed data
is described in Section 2. The global dense-gas and velocity
distribution is reported in Section 3. The dynamical origin and
the time-energy properties of the gas motion are discussed in
Section 4. A summary is given in Section 5.
2. Observation
G352.63-1.07 (G352 hereafter) is observed with the Atacama
Large Millimeter/submillimeter Array (ALMA) in the ATOMS
survey (Liu et al. 2020, 2022). The observation was performed
with both Compact 7 m Array and the 12 m array (C43-2 or C43-3
configurations) in Band 3. The restored data cube has an average
beam size of q q
´ = ´ = -
( )
2 5 2 1 PA 87
maj min . The
antenna baselines can cover the extended structures with a scale up
to ∼100″. The channel width and noise level vary with different
spectral windows. The H13
CO+
, CCH, and H CN
13 (1-0) lines
have Δvchan = 0.2 km s−1
and σrms = 5 mJy beam−1
(0.15 K). The
HCO+
(1-0) has Δvchan = 0.1 km s−1
and σrms = 9 mJy beam−1
(0.25 K). The CH3OH (211 − 110) lines have vchan = 1.4 km s−1
and σrms = 2 mJy beam−1
(0.08 K). The more detailed observing
conditions are presented in Liu et al. (2020).
3. Results
3.1. Filament and Cores
Figure 1(a) shows the 3 mm continuum emission and the
integrated H13
CO+
(1-0) emission (moment 0). Compared to
the chemically fresh molecules CCH and HC3N (Chen21,
Figure 3 therein), the H13
CO+
emission is more concentrated
toward the inner region of the filament structures. It shows an
S-shaped compact filament. The six major cores (Chen21) are
clearly resolved therein. The line intensity decreases toward
M4 and M5, which could be due to the gas dissipation caused
by their outflows (Appendix B).
Figure 1(b) shows the H13
CO+
emission overlaid on the
Spitzer/IRAC three-band color image (GLIMPSE survey;
Benjamin et al. 2003; Churchwell et al. 2009). Among the
dense cores, only M1 has a compact IR source. M2 to M5 are all
absent of IR point sources. The other two IR sources (M3b and
M6) are located on the western side of the filament. The IRAC
color magnitudes for M1 are [3.6]–[4.5] = 2.1 and [5.8]–
[8.0] = 1.0, which are similar to the color of Class-0 YSOs
(Megeath et al. 2012). M1 is also detected in 6.7 GHz methanol
maser but undetected in 6–8 GHz radio continuum emission
above the noise level of 3–8 mJy beam−1
(Walsh et al. 1998).
This indicates M1 to have a deeply embedded young massive
star. It has not yet caused significant ionization to the
surrounding medium. Figure 1(b) also shows the CH3OH (2-1)
emission. It has a compact morphology concentrated at M1.
The molecular spectra at the three inner cores are shown in
Figure 1(c). The H13
CO+
(1-0) exhibits a noticeable double-
peak profile at M1. The two components have a separation of
vblue − vred = −1.8 km s−1
. M2 and M3 both have a single-
velocity component within vlsr = ± 0.3 km s−1
, which are close
to the redshift component at M1. The HCO+
and CH3OH line
profiles are less resolved owing to high optical depth and low
spectral resolution, respectively. Nevertheless, we can still see
Figure 1. (a) The velocity-integrated intensity of the H13
CO+
(1-0) line (false-color) and 3 mm continuum. The contour levels are 4σrms (1.6 mJy beam−1
) to 84σrms
(peak) in step of 16σrms. (b) The H13
CO+
and CH3OH emission regions around the main filament, overlaid on the IRAC-RGB image (3.6, 4.5, and 8.0 μm bands). The
H13
CO+
contours are 15%–90% in 15% steps of the peak intensity (8.5 K km s−1
). The CH3OH contours are 10%–90% in 20% steps of the peak intensity (18.7 K
km s−1
). The dashed circles label the area of each core. (c) Upper and lower panels: the spectra at the selected core centers. The blue and red shaded areas indicate the
velocity ranges of the two velocity components, respectively. The vertical dashed line denotes the division between the blueshift (core M1) and main-filament
components.
2
The Astrophysical Journal, 955:104 (10pp), 2023 October 1 Ren et al.
3. these two lines inclined to the blueshift side. We also examined
the other two dense-gas tracers CCH and H CN
13 (1-0)
(Figure 3). They have similar velocity components to the
H13
CO+
(1-0). The molecular lines all indicate prominent
blueshift component at M1.
3.2. Physical Parameters and Gravitational Instability
The physical parameters of the cores are presented in
Table 1. The details of the calculation are described in
Appendix A. All the cores have comparable spatial sizes and
are nearly uniformly distributed along the filament, with an
average spatial interval of D =
( )
s 10 2
cores or (7 ± 1.5) ×
103
au.
From the observed parameters, we estimated the stability of
the cores from the critical mass (Bertoldi & McKee 1992;
McKee & Ostriker 2007; Li et al. 2013):
s
= +
= +
F
⎜ ⎟
⎛
⎝
⎞
⎠
( )
M M M
R
G
v
5
6
, 1
A
crit BE
eff
tot
2
2
wherein σtot is the effective velocity dispersion (see
Appendix A) and MBE and MΦ represent the upper-limit
masses to be supported by the turbulence and magnetic
pressures, respectively. MΦ depends on magnetic field strength
B and mass density ρ0 = μmHn0, which are included in Alfvén
velocity of pr
=
v B 4
A 0 . For the B value, we referred to the
B measurement of the magnetic field in other similar cold and
dense filaments (e.g., Ching et al. 2018; Liu et al. 2018). They
are found to have a bulk distribution of B = 0.5–1.0 mG.
Adopting this range, we can derive MΦ = 0.6 to 1.2 Me, which
only has a minor contribution to Mcrit. As shown in Table 1, all
the cores have >
M M
crit core, which indicates a subcritical state
if the turbulence can support them against the self-gravity.
The filament stability can be estimated from the critical line-
mass density (Ostriker 1964; Arzoumanian et al. 2013)
s
=
⎛
⎝
⎞
⎠
( )
M
l G
2
. 2
crit
tot
2
From the average line width of Δvfila(H13
CO+
) = 2.0 km s−1
,
we can derive σtot = 0.9 km s−1
and (M/l)crit;390 Me pc. In
comparison, the observed total mass (48 Me) and length (45″)
yield (M/l)obs;300 Me pc−1
. Considering the projection effect,
the actual value could be even smaller. Therefore the property
of (M/l)obs < (M/l)crit suggests a subcritical state also for the
entire filament. The turbulent condition of the filament and
cores should have a close interplay with other dynamical
features including the core collapse and escaping motion, as
discussed in Section 4.
4. Discussion
4.1. Resolving the Velocity Components
As shown above, the filament has an overall smooth and
compact morphology. The transfer flows (Chen21) and
outflows seem to only have a limited influence to the main
filament. As seen in optically thin lines, the blueshift motion of
M1 is still the most conspicuous feature over the entire
structure. Its dynamical origin should be further inspected.
Figure 2(a) to (c) shows the H13
CO+
(1-0) emission in four
different velocity channels. The ALMA 3 mm and the
Submillimeter Array1 mm (Chen21) dust continuum emis-
sions are also plotted in Figure 2(d) and (e) for comparison.
Figure 2(f) presents the position–velocity (PV) plot of the
H13
CO+
along the filament. It shows that the blue component
is mainly in the velocity range from −4 to −1 km s−1
and has a
spatial extension from offset = −16″ to +6″. In order to inspect
the gas motion, we plot the emission region in two velocity
intervals, denoted as low- and high-velocity components, or
LVC and HVC, respectively. We plot their emission regions in
Figure 2(a) to (c). One can see that the LVC is peaked at M1
and has a weak elongation toward M2, while the HVC is more
confined around M1. Their morphologies are both largely
different from the outflow lobes (Appendix B). They should
both trace the dense-core motion instead of outflow.
The filament component is mainly in the velocity range of
(−1.5,+1.5) km s−1
. Its emission region (false-color image in
Figure 2(a) to (e)) almost traces the entire gas structure and
shows a noticeable gap at M1 center. The redshift wing
component (1.5–2.2 km s−1
, yellow contours) includes two
separated patches, with one extending from M4 and M5 and
another around M3. They could trace the denser gas affected by
the outflow or transfer flow. Around M1, there are no evident
Table 1
The Physical Properties of the Cores
Parameters M1 M2 M2b M3 M4 M5
(Observed)
vlsr (H13
CO+
) (km s−1
) −2.5 −0.8 −0.6 +0.1 +1.0 +1.3
Tex (HCO+
) (K) 37 22 22 22 22 20
Tb (H13
CO+
) (K) 4.0 3.0 5.0 2.1 3.7 2.6
Δv (km s−1
) 2.5 2.3 1.8 2.2 1.8 1.7
Radius (arcsec)a
5 4 6 5 4 4
(Derived)
Ntot (1023
cm−2
)b
2.6 ± 0.3 2.2 ± 0.2 2.3 ± 0.3 2.4 ± 0.2 2.2 ± 0.2 2.2 ± 0.2
σtot (km s−1
) 1.1 0.9 0.8 1.0 0.7 0.7
Mass (Me) 12 ± 2 6 ± 2 11 ± 2 8 ± 2 7 ± 2 7 ± 2
mcrit (Me) 15 13 12 12 11 11
Notes.
a
Average radius deconvolved with the beam size.
b
Ntot is derived from H13
CO+
intensity using Equation (A4). For M4 and M5, the H13
CO+
emissions are noticeably dissipated by the outflows. We assumed them to
have same Ntot with M3 based on the fact that these cores also have comparable 3 mm continuum emissions.
3
The Astrophysical Journal, 955:104 (10pp), 2023 October 1 Ren et al.
4. redshift features at v > 1 km s−1
. The dust continuum
emissions (Figure 2(a), two right panels) show an overall
similar spatial extent with the H13
CO+
filament but have a
compact intensity peak rightly at M1, which is ∼3 times more
intense than the remaining filament.
The spatial correlation of the velocity components can also
be inspected from their intensity profiles as shown in
Figure 2(f) (lower panel). The dust continuum profiles (dashed
and dotted lines) rightly follow the blueshift component (blue
solid line). They all have a shoulder-like decreasing trend from
M1 to M2. This coherency suggests that the dense core M1
should be mainly associated with the blueshift gas.
Thegap on the filament is more clearly seen in the intensity
profile (red line in Figure 2(f), lower panel). It rightly coincides
with the M1 center of both the dust continuum and the blueshift
H13
CO+
profiles. For the H13
CO+
emission, if considering the
total intensity profile (black solid line), the blueshift component
would nicely fill the gap, making the intensity profile of the
entire filament much more flattened.
The CCH emission regions of the two components are
shown in Figure 3(a). The PV diagram of CCH is shown in
Figure 3(b). The emission regions and PV diagram of the
H CN
13 are shown in Figure 3(c) and (d), respectively. The
lower intensity around M1 along the filament can also be seen
in CCH (Figure 3(a) and (b)). Although its blue component is
more extended than that of H13
CO+
, it is still mainly
concentrated at the central cavity of the filament. The H CN
13
emission is more concentrated at M1, so the central intensity
decline is not evident. But from its PV diagram, one can still
see a comparable velocity separation of v − vlsr = − 2 km s−1
between the blueshift component and the main filament. And it
is also closely overlapped with the H13
CO+
and CCH spectra
for the blueshift peak (Figure 6(c)). The three molecular lines
thus consistently suggest the blueshift component to be the
dominant one at M1. In other words, the dense core is having a
bulk motion relative to the rest of the filament.
Based on their spatial and velocity features, M1 and the main
filament could have two possible configurations. M1 can be
either leaving the filament on the front side or moving toward it
from behind. From the PV plot (Figure 2(b)), one can see the
blue component connected to the main filament both toward
north and south, around offset = +5″ and −15″, respectively.
The PV diagrams of the CCH and H CN
13 (1-0) lines (Figure 3,
right column) show the similar connection feature between M1
and the main filament in the two directions. M1 should thus be
originally formed in the filament and have obtained the
blueshift motion only during the recent time.
4.2. Driving Force of the Blue Component
The multiple velocity components in G352 are comparable
to other filaments with prominent kinematical features. As
shown in previous studies, undisturbed linear filaments tend to
have moderate fluctuation of |v − vsys| „ 1.0 km s−1
around
their internal cores (e.g., Punanova et al. 2018; Bhadari et al.
2020). More complicated fiber-composed filaments also have
similar velocity variation within 1 km s−1
(Hacar et al. 2017;
Clarke et al. 2018). Stronger kinematical features of several
kilometers per second are seen in filaments with collapse
(Henshaw et al. 2014; Chen et al. 2019; Ren et al. 2021; Cao
et al. 2022; Li et al. 2022) or interactions (Shimajiri et al. 2019;
Anathpindika & Francesco 2021). The velocity fluctuations in
G352 resembles those most active ones. The blueshift motion
(−2 km s−1
) and its spatial scale (5″ or 3500 au) lead to a
gradient of ∼250 km s−1
pc−1
, which resembles those most
intensely collapsing filaments (e.g., Peretto et al. 2013;
Montillaud et al. 2019; Beuther et al. 2021; Hu et al. 2021; Cao
et al. 2022).
In collapsing or fiber-composed filaments, the global
velocity field is often entangled with the individual core
motions. It is therefore uncertain if the cores are co-moving
with the filament or already separated. In comparison, G352
presents an example of clearly separated velocity components.
In fact, the main filament is also inclined to the blueshift side
around M1 toward −0.5 km s−1
(Figure 2(b)). The filament
could thus have a co-moving tendency with M1. In particular,
as shown in Figure 2(a), the HVC (v = (−4, −3) km s−1
) is
narrowly confined between the northern and southern segments
of the entire filament. This increases the evidence that the core
and filament motions are closely related.
The mass transfer flows (Chen21) provide a viable
mechanism to initiate the filament collapse. Since the flows
are observed from one-sided molecular line wings instead of
strong infall signatures, they would provide a moderate mass
accumulation to the inner filament (between M2 and M3). Once
the mass assembly exceeds the threshold of (M/l)crit or Mcrit , it
would possibly induce a major collapse. One can see that the
transfer flows exhibit no evident mass assembly at their arrival
Figure 2. (a)–(e) Contours: emission region of the H13
CO+
(1-0) line in three velocity intervals. The background image is the H13
CO+
emission in (−1.5,+1.5) km s−1
(red-center component). For the blue-wing component, the contour levels are 4, 6, and 8 times of the rms level (0.3 K km s−1
). For the other components, the contour
levels are 10%–90% in 20% steps of the peak intensity, which is 15, 11, and 3 K km s−1
for the blue-center, red-center, and red-wing, respectively. The green arrows label
the mass transfer flow directions onto the main filament (Chen21). The green circles label the possible arrival points of the transfer flows onto the filament. (f) PV plot and
intensity profile along the major axis of the main filament. The sampling direction is labeled in dashed line in panel (a). The vertical dashed lines denote the projected
offset of the three dense cores on the sampling direction. The horizontal dotted line represents the average systemic velocity of the filament.
4
The Astrophysical Journal, 955:104 (10pp), 2023 October 1 Ren et al.
5. points on the inner filament (Figure 2). This also indicates that
the flows should have a further propagation toward M1.
4.3. Energy Scales of the Gas Components
The filament collapse and core escape can also be examined
from their energy scales. From the core mass and its escaping
velocity, the kinetic energy of M1 is estimated to be
= - ´
( )
E m v v 2 3.5 10
k core blue red
2 44 erg. This would
represent a lower limit due to the projection effect. In
comparison, the turbulent energy of the entire filament is
s
= = ´
( )
E m 2 2.5 0.5 10
turb tot nt
2 44 erg. As for the magn-
etic energy, from the speculated B-range (Section 3.2), we can
estimate = =
E m v 2 2
B A
tot
2
to 8 × 1043
erg. Eturb and EB
values characterize the entire filament. The fraction to reach
M1 could be even lower and thus cannot be solely responsible
for the core motion.
The collapsing energy can be estimated as D =
Ep,coll
-
[( ) ( )]
Gm r r
1 1
in
2
1 0 , which involves the initial and final
radii (r0 and r1) of the collapsing mass mcoll. Assuming that the
major collapse is taking place between M2 and M3, we can
adopt = D
r s
0 cores. Together with the current radius and mass
of M1, we derived ΔEp,coll ; 6 × 1044
erg, which could be
sufficient to accelerate M1.
As seen in the PV diagram (Figure 2(b)), the inner region has
a typical line width of Δv 1.8 km s−1
for both the blueshift
component and the main filament. It rapidly declines toward
the outer part, reaching a transonic level of Δv ; 0.7 km s−1
(σnt = 0.4 km s−1
) toward offset = ±20″. The low-Δv areas
over the filament could represent the fraction less affected by
the collapse. Adopting the average value (0.9 km s−1
) in
Equation (2), we can derive (M/l)crit;150 Me pc−1
, which is
much smaller than (M/l)obs and should reflect the supercritical
condition before the major collapse.
Figure 4 shows the velocity distributions over the core and
filament in all three lines. The low-turbulence areas with Δv
down to 0.6 km s−1
can be seen in all three species. The CCH
and H13
CO+
emission regions both exhibit the low values
Figure 3. Left column: the emission regions of the blue- (contours) and redshifted (false-color) components in CCH and H CN
13
(1-0) lines. The contour levels are
20%–90% of the peak intensity. Right column: the PV diagrams of the two molecular lines. the H CN
13
emission at vlsr = 2–4 km s−1
is from another hyperfine
component (HFC)of F = 1–1. The HFCs of H CN
13
are separated for 6–7 km s−1
and would not blend with each other. The CCH (1-0) emission shows an additional
small blueshift wing around M3, which should correspond to the transfer flow onto the filament (Chen21). This feature is not seen in other lines probably because of
their lower optical depths.
5
The Astrophysical Journal, 955:104 (10pp), 2023 October 1 Ren et al.
6. down to Δv ; 0.7 km s−1
, while the higher values mainly
appear between M1 and M3. The H CN
13 line is more
concentrated on dense cores, which could be due to its
chemical bias toward the protostellar stage. Along the filament,
the H CN
13 line-width variation is mainly between 1.2 and
1.4 km s−1
, which is comparable to average values of CCH and
H13
CO+
lines.
4.4. Time Scales of the Gas Motion
Figure 5(a) shows the ridge lines of the main filament and
the blueshift component (M1 and southern extension). The two
components have a transverse offset of Δsesc = 0″ to 2 3 along
the filament. We plot the Δsesc and |vblue − vred| profiles along
the filament in Figure 5(b). One can see that the two quantities
have a coherent variation trend. At M1 and the second velocity
peak near M2 (offset = −10″), the velocity and transverse
offsets both reach a local maximum.
The transverse separation as a function of time can be
estimated as q
D = -
( )
s t v v tan
esc esc blue red , wherein θ is the
inclination angle between the gas motion and sight line.
Adopting θ = (45 ± 10)°, we can derive a timescale of
tesc ; (4 ± 2) × 103
yr for the blueshift motion. It isclose to
the outflow age of tout = 3.6 × 103
yr (Appendix A). The two
values should together characterize the star-forming age
in G352.
If the core escape started during the filament collapse, one
would expect an overall collapsing time sufficiently longer
Figure 4. The peak velocity and line-width distributions of the two components as observed in three molecular lines. The velocity ranges to measure the blueshift-core
and main-filament components are (−4, − 1.5) and (−1.5, 2) km s−1
, respectively. Left two columns: the radial-velocity distributions of the two components. Right
two columns: the line-width distributions of the two components.
6
The Astrophysical Journal, 955:104 (10pp), 2023 October 1 Ren et al.
7. than tesc. From the recent semi-analytical work (Clarke &
Whitworth 2015), the filament could have a collapsing time of
r
= + -
( )( ) ( )
t A G
0.49 0.26 , 3
coll 0 0
1 2
wherein A0 is the aspect ratio of the filament. Assuming that the
major collapse took place in the inner region between M2 and
M3, from the filament length (l ; 22″) and width (w ; 5″), we
can derive tcoll ; 6 × 104
yr. It could roughly represent the
dense-core formation time. For M1, it then implies a mass
accretion rate of = ´ - -
M M t M
1.8 10 year
acc core coll
4 1,
which is comparable to the rate of the transfer flows (Chen21).
The collapse toward the center could be dominated by the two
colliding flows along the filament. The flows would rapidly
increase the central density and develop an anisotropic
instability. The highly compressed gas would then move
toward the transverse directions, initiating the observed motion.
A schematic view of the collapse and core acceleration is
shown in Figure 5(c).
The collapsing time could be compared with the turbulence-
increasing time of the filament. From the turbulence level of the
inner filament (σnt ; 0.8 km s−1
), we can derive a dynamical
timescale of s
= D ´
t s 8 10
dyn cores nt
4 yr, which is also
similar to tcoll. As shown in Figure 4, the line-width
distributions of H13
CO+
and CCH are both steeply increased
between M1 and M3 with a scale of ΔV 1.0 km s−1
. This
also provides evidence that the turbulence was increased by the
recent dynamical evolution and thus has not yet reached a
uniform state over the filament.
Although the filament collapse could have sufficient energy
and time to initiate the core motion, other dynamical origins for
the blue component are still not fully excluded. In particular, it
could also be a fiber-like component. The fibers in massive
filaments are observed on larger spatial scales (>0.2 pc) in a
few recent studies (Shimajiri et al. 2019; Cao et al. 2022).
Those fibers are only loosely aligned or intertwined along the
filament axis. They have transverse separations up to several
0.1 pc and do not have two-end connections like in the case of
M1. The fibers could be increasingly separated with the
filament age. For G352, the separation would be
Δsesc (vblue − vred)tcoll ; 2.5 × 104
au (36″), which is unrea-
sonably large compared to the observed spatial scales. To
maintain the observed Δsesc, the fibers should originally have
much smaller velocity difference (=2 km s−1
) and still need a
recent collapse to provide the kinetic energy and reach the
escaping velocity.
5. Summary
Based on the velocity distribution of H13
CO+
and other dense-
gas tracers, we found that the most massive core M1 (12 Me) is
connected to the main filament but has a blueshift of
- - -
¯
v v 2 km s
core sys
1. The core motion has a kinetic energy
of 3.5 × 1044
erg and timescale of only ∼4000 yr. As a unique
example, M1 reveals the very beginning of a massive YSO
escaping from its birth site. It confirms the possibility that YSO
can leave the filament along the transverse direction.
Among the available mechanisms, only the filament collapse
could provide enough energy to initiate the core escape. A
recent collapse is also needed to generate the massive star
therein. It can be also responsible for the drastic velocity and
turbulence variations over the filament. As the core motion is
taking place, a central gap is formed rightly at its location on
the remaining part of the filament.
According to the energy and time comparisons, the process
of core escape could have three major steps: (i) the filament had
a relatively low turbulence, with moderate contraction and
fragmentation into the dense cores; (ii) because of the transfer
flows, the inner region became more massive and unstable and
eventually initiated a major collapse; (iii) M1 was strongly
compressed by the collapsing gas to start the escaping motion,
while the rest energy could be transferred to the filament to
increase the turbulence.
Figure 5. (a) The ridge lines of the two velocity components, blue component in blue line and dots, red-center component (main filament) in yellow line and dots. The
dot size is proportional to the integrated intensity. The arrows denote the projected moving direction of each component expected on the sky plane. (b) The transverse
offset and velocity difference between the ridge lines of the two components along the filament axis. In the lower panel, the blue and red dots represent the peak radial-
velocity profile of the two components, respectively. The gray dots represent |vblue − vred|. (c) A schematic view of the gas motion on the filament and cores.
7
The Astrophysical Journal, 955:104 (10pp), 2023 October 1 Ren et al.
8. Based on the result in G352, one can examine other
filaments with steep velocity gradients to see if similar core
motions are taking place. A larger sample will help evaluate the
universality of such collapse-induced YSO escape and estimate
its contribution to the YSO dispersion over molecular clouds.
Acknowledgments
The authors would like to thank the referees for the
constructive comments. This work is supported by the National
Natural Science Foundation of China (NSFC Grant Nos.
11988101, 12041302), National Key R&D Program of China
No. 2022YFA1602901, NSFC Grant Nos. 11973051,
U1931117, 11725313, U2031117,12103069, and the Interna-
tional Partnership Program of the Chinese Academy of
Sciences (grant No. 114A11KYSB20210010). T.L. acknowl-
edges the support by the international partnership program
of Chinese Academy of Sciences through grant No.
114231KYSB20200009, and Shanghai Pujiang Program
20PJ1415500. L.B. gratefully acknowledges support by ANID
BASAL project FB210003. A.S. gratefully acknowledges
support by the Fondecyt Regular (project code 1220610), and
ANID BASAL projects ACE210002 and FB210003. C.W. was
supported by the Basic Science Research Program through the
National Research Foundation of Korea (NRF) funded by the
Ministry of Education, Science and Technology (NRF-
2019R1A2C1010851), and by the Korea Astronomy and
Space Science Institute grant funded by the Korea government
(MSIT; project No. 2023-1-84000). C.E acknowledges the
financial support from grant RJF/2020/000071 as a part of the
Ramanujan Fellowship awarded by the Science and Engineer-
ing Research Board (SERB), India. E.M. is funded by the
University of Helsinki doctoral school in particle physics and
universe sciences (PAPU).
This paper makes use of the following ALMA data: ADS/
JAO.ALMA 2019.1.00685.S. ALMA is a partnership of ESO
(representing its member states), NSF (USA), and NINS
(Japan), together with NRC (Canada), MOST and ASIAA
(Taiwan region), and KASI (Republic of Korea), in cooperation
with the Republic of Chile. The Joint ALMA Observatory is
operated by ESO, AUI/NRAO, and NAOJ.
The Spitzer GLIMPSE legacy survey data can be down-
loaded at NASA/IPAC Infrared Science Archive (https://irsa.
ipac.caltech.edu/irsaviewer/).
Appendix A
Deriving the Dense-core Properties
The total column density of a molecular species is estimated
from the optically thin lines (Caselli et al. 2002; Henshaw et al.
2014) as
p
l
n
=
-
´
- -
´
-
n n
( ) ( )
( )
( )
( )
( )
N
I
A
g
g J T J T
h k T
Q T
g El k T
8 1
1
1 exp
exp
, A1
u
l ex
B
l B
tot,mol
tot
3
bg
ex
rot ex
ex
wherein Itot = ∫Tbdv is the total intensity of the line profile, A is
the Einstein coefficient for spontaneous decay, and gu and gl
are the statistical weights for the upper and lower states,
respectively. = -
( ) [ ( ) ]
J T T T T
exp 1
0 0 is the Planck-
corrected brightness temperature with the reference value of
T0 = hν/k. Qrot(Tex) is the partition function, and λ and ν are the
wavelength and frequency of the line transition, respectively.
Tbg = 2.73 K is the cosmic background temperature. kB and h are
the Boltzmann and Planck constants, respectively. The total gas
column density is N(H2) = Ntot,mol/Xmol, wherein Xmol is the
molecular abundance. For the H13
CO+
abundance, Gerner et al.
(2014) measured Xmol(H13
CO+
) = 0.9 to 1.5 × 10−9
from a
large sample of dense cores from IRDC to hot-core stage. We
adopt Xmol(H13
CO+
) = (1.2 ± 0.3) × 10−9
for the calculation
of G352.
We also tried to use CCH and H CN
13 (1-0) lines to calculate
Ntot. They provide comparable values on 1023
cm−2
scale. The
optical depth of the molecular lines are examined using (Bell
et al. 2014)
t
pn
n
=
D
- -
⎜ ⎟ ⎜ ⎟
⎛
⎝
⎞
⎠
⎡
⎣
⎢
⎛
⎝
⎞
⎠
⎤
⎦
⎥
( )
c A g N
vQ
E
kT
h
kT
8
exp exp 1 . A2
ij u ij
3
3
tot
rot
up
rot rot
In calculation, we also adopted the average abundances in the
young high-mass protostellar objects in Gerner et al. (2014),
which are Xmol(CCH) = 5.0 × 10−8
and =
( )
X H CN
mol
13
= ´ -
( )
X HCN 80 4.7 10
mol
11. From the physical condi-
tion at M1 of Ntot,mol = 2.6 × 1023
cm−2
and Tex = 37 K, we
estimated τ(CCH) = 1.1, τ(H13
CO+
) = 0.12, and t =
( )
H CN
13
0.06.
From N(H2) distribution, we can estimate the core mass to be
ò
m
= ( )
m m N dA
H
core H 2 , wherein the integration is made over
the core area. The cores are irregular and not fully separated
from the filament. To prevent complexity, we assumed the
cores to have spherical or elliptical shapes. M3 and M5 indeed
have noticeable elongation and thus are assumed to be
elliptical, while other cores are considered to be spherical.
The core region is adjusted to cover the emission region above
the extended emission over the filament (3 K km s−1
). The core
areas are plotted in Figure 1(b).
In deriving Ntot,mol, we adopt the excitation temperature of
HCO+
(1-0) lines (Figure 1(c)). Assuming it is optically thick,
it can be estimated using
= -
( ) ( ) ( )
T J T J T . A3
b ex bg
The calculation leads to Tex ; 37 K for M1 and 22 ± 3 K for other
cores. The second value is comparable to the dust temperature
derived from SED fitting (Chen21), whereas the higher value at
M1 should reflect the stellar heating. From the CH CN
3 population
diagram, Chen21 derived a much higher temperature of Trot = 165
K at M1. This value should incline to the small amount of
shocked gas, whereas the major fraction of the filament should
still be much cooler due to the absence of ionized gas and strong
IR emission. Their temperature range is comparable with the
values of pre-stellar cold dense cores (e.g., Xie et al. 2021),
suggesting an early evolutionary stage on average for the filament.
Moreover, if assuming Tex(H13
CO+
) = 165 K, one can derive
N(H2) = 7 × 1023
cm−2
and =
m M
30
core for M1. This value is
unreasonably high as it takes up more than one-half of the total
filament mass.
8
The Astrophysical Journal, 955:104 (10pp), 2023 October 1 Ren et al.
9. The total velocity dispersion of the core is estimated from the
observed line width Δv as
s s s
m
= +
= +
D
- ( )
k T
m
v k T
m
8 ln 2
, A4
tot th
2
nt
2
B kin
H
2
B kin
mol
wherein mmol is the molecular mass. The thermal part is
s
m
= ( )
k T
m
, A5
th
B kin
H
and the nonthermal part is
s =
D
- ( )
v k T
m
8 ln 2
. A6
nt
2
B kin
mol
In calculation we adopted a kinetic temperature of Tkin = 37 K
for M1 and Tkin = 22 K for other cores. They lead to σth = 0.29
to 0.36 km s−1
, respectively. In comparison, the average line
width of Δv = 1.5 km s−1
leads to σnt = 0.64 km s−1
, which is
not largely affected by Tkin and σth.
Appendix B
Outflow Properties
The outflow emission is detected from high-velocity line wings
in the HCO+
(1-0) lines. Its emission region and spectra are
shown in Figures 6(a) and (b), respectively. The blue- and
redshift line wings are both strongly detected at M4, which shows
the velocity ranges of (−20, − 6) km s−1
for the blue lobe and (5,
20) km s−1
for the red one. As seen in Figure 6(a), compared with
the CO outflow (Chen21), the HCO+
is concentrated around M4
and M5, suggesting that the outflow should be launched from this
area. From the spatial extensions of the outflow lobes, we can see
at least two bipolar outflows, as indicated by the dashed lines.
The outflow extensions are not fully overlapped with M4 and
M5. It is uncertain if this is due to additional driving sources or
the time-variation of the outflow morphology. One thing for sure
is that the outflow intensity is much weaker at M1, and the red
lobe is almost undetected. If M1 also has a contribution to the
blueshift gas, it should be more likely ejected in the process of
core collapse and escape than due to the protostellar outflow.
From the HCO+
line-wing intensities and outflow emission
areas, the outflow lobes are found to have masses mblue =
0.20 Me and mred = 0.24 Me. And the average radius is Rout =
(8 ± 3)″ = (5.5 ± 2) × 103
au. Assuming an average velocity of
vout = 8 km s−1
, the outflow age is derived to be tout =
Rout/vout = (3.5 ± 1) × 103
yr.
Figure 6. (a) The HCO+
outflow lobes overlaid on the HCO+
excitation temperature map. The line intensity is converted to Tex using Equation (A3). The contour
levels are 15%–90% of the maximum intensity, which is 22.6 and 22.9 K km s−1
for the blue and red lobes, respectively. (b, c) The molecular spectra at selected cores.
For each spectrum, the horizontal line represents the zero-level baseline. The vertical dashed line denotes the division between the blueshift gas (M1 core) and main-
filament components.
9
The Astrophysical Journal, 955:104 (10pp), 2023 October 1 Ren et al.
10. ORCID iDs
Zhiyuan Ren (任致远) https:/
/orcid.org/0000-0003-4659-1742
Xi Chen (陈曦) https:/
/orcid.org/0000-0002-5435-925X
Tie Liu (刘铁) https:/
/orcid.org/0000-0002-5286-2564
Leonardo Bronfman https:/
/orcid.org/0000-0002-
9574-8454
Fengwei Xu (许峰玮) https:/
/orcid.org/0000-0001-5950-1932
Siyi Feng (冯思轶) https:/
/orcid.org/0000-0002-4707-8409
Hongli Liu (刘洪礼) https:/
/orcid.org/0000-0003-3343-9645
Fanyi Meng (孟繁一) https:/
/orcid.org/0000-0002-5927-2049
Amelia M. Stutz https:/
/orcid.org/0000-0003-2300-8200
Shanghuo Li (李尚活) https:/
/orcid.org/0000-0003-1275-5251
Chang Won Lee https:/
/orcid.org/0000-0002-3179-6334
Ke Wang (王科) https:/
/orcid.org/0000-0002-7237-3856
Di Li (李菂) https:/
/orcid.org/0000-0003-3010-7661
Chakali Eswaraiah https:/
/orcid.org/0000-0003-4761-6139
Anandmayee Tej https:/
/orcid.org/0000-0001-5917-5751
Long-Fei Chen (陈龙飞) https:/
/orcid.org/0000-0002-
9703-3110
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