This document summarizes early results from the Herschel Gould Belt survey of the IC5146 molecular cloud. It reveals a complex network of filaments identified in the cloud, which are shown to be the main sites of prestellar core formation. Analysis of 27 filaments finds that their radial column density profiles fall off with radii as r^-1.5 to r^-2.5. Remarkably, the filaments seem to have a narrow distribution of widths centered around 0.1 pc, in contrast to a broader distribution of central Jeans lengths. This characteristic width corresponds to the sonic scale below which turbulence becomes subsonic, supporting the argument that filaments may form from dissipating large-scale turbulence.
An exceptional xray_view_of_the_young_open_cluster_ngc6231Sérgio Sacani
The XMM-Newton satellite observed the young open star cluster NGC 6231 for a total of 180 kiloseconds, providing an unprecedented X-ray view. Around 600 point-like X-ray sources were detected, including many early-type O stars. The data helped refine the relationship between X-ray and bolometric luminosities for O stars, finding less scatter than previously thought, with the main exception being X-ray emission from wind interactions in binary systems. The data also provided insight into the low-mass pre-main sequence star population and star formation history of the cluster.
Discovery of xray_emission_from_young_suns_in_the_small_magellaniccloudSérgio Sacani
1) The document reports on the discovery of extended X-ray emission from the young star cluster NGC 602a in the Small Magellanic Cloud based on Chandra X-ray Observatory observations.
2) X-ray emission was detected from the cluster core, which has the highest stellar density, and from a surrounding dusty ridge.
3) The X-ray emission from the cluster core is suggested to originate from an ensemble of low- and solar-mass pre-main-sequence stars, while the emission from the dusty ridge is attributed to embedded young stellar objects known from infrared studies.
Star formation history_in_the_smc_the_case_of_ngc602Sérgio Sacani
This document summarizes a study of the star formation history in the NGC 602 region of the Small Magellanic Cloud based on Hubble Space Telescope observations. Deep photometry reveals numerous pre-main sequence stars as well as young stars on the main sequence, allowing the study of star formation into recent times. New pre-main sequence stellar evolutionary tracks are presented. A stellar population synthesis code is used to derive the best estimate of the star formation history by comparing observed and synthetic color-magnitude diagrams. The star formation rate in the region has increased over the past tens of Myr, reaching 0.3-0.7×10−3 M☉ yr−1 in the last 2.5 Myr, comparable to
Our deep, wide-field imaging of M101 and its surrounding environment reveals:
1) M101's disk extends to nearly 25 arcminutes (50 kpc), three times the measured optical radius, with an asymmetric plume of light to the northeast following the extended HI disk.
2) This outer plume has very blue colors, suggesting a somewhat evolved young stellar population, while another redder spur is detected to the east.
3) No evidence is found of very extended tidal tails around M101 or its companions despite signs of past interactions shaping M101's asymmetry.
4) The detection of starlight at such large radii allows studying the stellar populations and star formation histories in M101's outer disk
This document summarizes a study using deep Chandra observations of the Seyfert 1 galaxy NGC 4151. The observations allow examination of emission line morphology in the inner 150 pc region with high spatial resolution. The maps show structures correlated with the radio outflow and optical emission. There is evidence for jet-gas cloud interactions, including regions with elevated NeIX/OVII ratios and X-ray emission exceeding expectations from nuclear photoionization alone, suggesting collisional ionization. Constraints are also placed on the spatial distribution of iron Kα emission, finding less than 5% originates beyond 150 pc, in disagreement with a prior claim of 65% from larger regions.
1. Chandra observations of the galaxy NGC 3351 revealed X-ray emission from its circumnuclear star-forming ring that is composed of numerous point-like sources embedded in diffuse hot gas.
2. The morphology of the X-ray emission is similar to but not identical with UV and H-alpha hot spots in the ring, which can be understood if star formation occurs through intermittent starbursts around the ring with different emissions tracing later evolutionary stages.
3. X-ray emission also extends beyond the ring, which is interpreted as outflowing gas from the ring into the disk and halo of NGC 3351, providing evidence for confined outflow near the plane but less restricted outflow perpendicular to
Extended x ray emission in the h i cavity of ngc 4151- galaxy-scale active ga...Sérgio Sacani
The document summarizes the discovery of diffuse soft X-ray emission extending about 2 kpc from the active nucleus of NGC 4151, filling the cavity of H i material. The X-ray emission has a luminosity of about 1039 erg s-1 and can be fit with either a thermal plasma model with a temperature of around 0.25 keV, or a photoionized model. This interaction between the AGN and interstellar medium implies the last episode of high nuclear activity occurred relatively recently, around 104 years ago.
X ray emission-from_strongly_asymmetric_circumstellar_material_in_the_remnant...Sérgio Sacani
This document summarizes a study of X-ray emission from circumstellar material (CSM) in the remnant of Kepler's supernova. The researchers used a statistical technique to isolate X-ray emission from CSM versus ejecta based on spectral characteristics. They found that most CSM is distributed along the bright north rim, but substantial amounts are also projected against the center, indicating a disk-like distribution of CSM from the progenitor system before the supernova. Hydrodynamic simulations support an AGB star companion as the origin of the asymmetric CSM. Quantitative analysis of magnesium emission identifies CSM and requires Kepler to have originated from a close binary system.
An exceptional xray_view_of_the_young_open_cluster_ngc6231Sérgio Sacani
The XMM-Newton satellite observed the young open star cluster NGC 6231 for a total of 180 kiloseconds, providing an unprecedented X-ray view. Around 600 point-like X-ray sources were detected, including many early-type O stars. The data helped refine the relationship between X-ray and bolometric luminosities for O stars, finding less scatter than previously thought, with the main exception being X-ray emission from wind interactions in binary systems. The data also provided insight into the low-mass pre-main sequence star population and star formation history of the cluster.
Discovery of xray_emission_from_young_suns_in_the_small_magellaniccloudSérgio Sacani
1) The document reports on the discovery of extended X-ray emission from the young star cluster NGC 602a in the Small Magellanic Cloud based on Chandra X-ray Observatory observations.
2) X-ray emission was detected from the cluster core, which has the highest stellar density, and from a surrounding dusty ridge.
3) The X-ray emission from the cluster core is suggested to originate from an ensemble of low- and solar-mass pre-main-sequence stars, while the emission from the dusty ridge is attributed to embedded young stellar objects known from infrared studies.
Star formation history_in_the_smc_the_case_of_ngc602Sérgio Sacani
This document summarizes a study of the star formation history in the NGC 602 region of the Small Magellanic Cloud based on Hubble Space Telescope observations. Deep photometry reveals numerous pre-main sequence stars as well as young stars on the main sequence, allowing the study of star formation into recent times. New pre-main sequence stellar evolutionary tracks are presented. A stellar population synthesis code is used to derive the best estimate of the star formation history by comparing observed and synthetic color-magnitude diagrams. The star formation rate in the region has increased over the past tens of Myr, reaching 0.3-0.7×10−3 M☉ yr−1 in the last 2.5 Myr, comparable to
Our deep, wide-field imaging of M101 and its surrounding environment reveals:
1) M101's disk extends to nearly 25 arcminutes (50 kpc), three times the measured optical radius, with an asymmetric plume of light to the northeast following the extended HI disk.
2) This outer plume has very blue colors, suggesting a somewhat evolved young stellar population, while another redder spur is detected to the east.
3) No evidence is found of very extended tidal tails around M101 or its companions despite signs of past interactions shaping M101's asymmetry.
4) The detection of starlight at such large radii allows studying the stellar populations and star formation histories in M101's outer disk
This document summarizes a study using deep Chandra observations of the Seyfert 1 galaxy NGC 4151. The observations allow examination of emission line morphology in the inner 150 pc region with high spatial resolution. The maps show structures correlated with the radio outflow and optical emission. There is evidence for jet-gas cloud interactions, including regions with elevated NeIX/OVII ratios and X-ray emission exceeding expectations from nuclear photoionization alone, suggesting collisional ionization. Constraints are also placed on the spatial distribution of iron Kα emission, finding less than 5% originates beyond 150 pc, in disagreement with a prior claim of 65% from larger regions.
1. Chandra observations of the galaxy NGC 3351 revealed X-ray emission from its circumnuclear star-forming ring that is composed of numerous point-like sources embedded in diffuse hot gas.
2. The morphology of the X-ray emission is similar to but not identical with UV and H-alpha hot spots in the ring, which can be understood if star formation occurs through intermittent starbursts around the ring with different emissions tracing later evolutionary stages.
3. X-ray emission also extends beyond the ring, which is interpreted as outflowing gas from the ring into the disk and halo of NGC 3351, providing evidence for confined outflow near the plane but less restricted outflow perpendicular to
Extended x ray emission in the h i cavity of ngc 4151- galaxy-scale active ga...Sérgio Sacani
The document summarizes the discovery of diffuse soft X-ray emission extending about 2 kpc from the active nucleus of NGC 4151, filling the cavity of H i material. The X-ray emission has a luminosity of about 1039 erg s-1 and can be fit with either a thermal plasma model with a temperature of around 0.25 keV, or a photoionized model. This interaction between the AGN and interstellar medium implies the last episode of high nuclear activity occurred relatively recently, around 104 years ago.
X ray emission-from_strongly_asymmetric_circumstellar_material_in_the_remnant...Sérgio Sacani
This document summarizes a study of X-ray emission from circumstellar material (CSM) in the remnant of Kepler's supernova. The researchers used a statistical technique to isolate X-ray emission from CSM versus ejecta based on spectral characteristics. They found that most CSM is distributed along the bright north rim, but substantial amounts are also projected against the center, indicating a disk-like distribution of CSM from the progenitor system before the supernova. Hydrodynamic simulations support an AGB star companion as the origin of the asymmetric CSM. Quantitative analysis of magnesium emission identifies CSM and requires Kepler to have originated from a close binary system.
This document summarizes long-slit spectroscopic observations of four planetary nebulae - Hb 4, IC 4634, NGC 6369, and NGC 7354 - conducted with the Palomar 5 m telescope. The observations were aimed at investigating the spectroscopic properties of microstructures like jets and FLIERs (fast, low-ionization emission regions) seen in these planetary nebulae. Physical conditions and chemical abundances were derived from emission line ratios along the structural axes of the microstructures. In most cases, no evidence of shock activity or nitrogen-to-oxygen abundance anomalies was found, unlike some previous studies of similar structures. Microstructures appear to be a heterogeneous class of structures aside from their generally supersonic
1) NGC 474 is a lenticular galaxy surrounded by shells of matter whose origin is still debated - they could have formed from merging with a low mass galaxy or gravitational interaction with satellite galaxy NGC 470.
2) Photometric analysis of NGC 474 found its surface brightness profile is typical for a lenticular galaxy even in the center, and the color indices of the shells are consistent with NGC 474.
3) This implies the shells most likely originated from gravitational interaction with NGC 470 rather than from merging, as merging would have disturbed the central surface brightness profile.
This document summarizes a study that used optical, infrared, and submillimeter data to examine star formation in the region surrounding the IC 348 star cluster and the nearby Flying Ghost Nebula. The study identified 13 protostars driving protostellar outflows in the region, including HH 211 which had not previously been detected at visible wavelengths. The region surrounding the Flying Ghost Nebula shows ongoing star formation with outflows similar to other areas of moderate star formation in Perseus. A candidate bent jet was also found, which may have been ejected from a multiple star system near IC 348.
The discovery of a giant arc associated with the galaxy cluster IDCS J1426.5+3508 at z=1.75 is reported. HST imaging reveals an arc-like object with a length-to-width ratio greater than 10, located near the brightest cluster galaxy. Attempts to measure the redshift of the arc through spectroscopy were unsuccessful. The existence of such a massive, strongly lensing cluster at this early epoch poses challenges for the standard ΛCDM model of structure formation.
Type iax supernovae_a_new_class_of_stellar_explosionSérgio Sacani
Type Iax supernovae are a new class of stellar explosions that are spectroscopically similar to Type Ia supernovae but have lower maximum light velocities and peak magnitudes. They typically have lower ejecta masses and hotter photospheres than Type Ia. The progenitor system is likely a carbon-oxygen white dwarf that accretes matter from a helium star companion, resulting in a deflagration explosion that does not fully disrupt the white dwarf. Type Iax events occur about 31 times as frequently as Type Ia supernovae.
This document summarizes the results of a study using Herschel Space Observatory data to analyze the physical properties of dust in the RCW 120 H ii region. The study finds:
1) Dust temperatures in RCW 120 range from around 30 K in the interior decreasing to 20 K in the photo-dissociation region and 10 K in nearby infrared dark clouds.
2) There is tentative evidence of an anti-correlation between dust temperature and the dust emissivity index β, with cooler dust having higher β values, consistent with some previous studies.
3) RCW 120 appears to be in the process of destroying its photo-dissociation region boundary and leaked radiation from the interior may be influencing the
This document summarizes the discovery of a stellar tidal stream around the nearby dwarf galaxy NGC 4449 using deep imaging. The stream implies a massive dwarf spheroidal progenitor that is disrupting and depositing stars into NGC 4449's halo. The luminosity ratio between the two galaxies is around 1:50, but their dynamical mass ratio including dark matter may be 1:10-1:5. This "stealth merger" suggests that satellite accretion can significantly build up stellar halos of low-mass galaxies and possibly trigger their starbursts.
This study uses deep Chandra observations to examine the X-ray morphology of the circum-nuclear region of NGC 4151 on spatial scales down to 30 pc. Extended soft X-ray emission is detected out to 1.3 kpc from the nucleus, farther than seen in previous studies. The X-ray emission is more absorbed towards the boundaries of the ionization cone and perpendicular to the bicone, suggesting absorption by a torus. The innermost X-ray emission, coincident with H2 emission and dusty spirals, supports X-ray excitation of molecular gas. The extended X-ray emission may be due to hot gas heated by the AGN outflow or photoionized by past AGN activity.
This document summarizes star forming regions in the constellation of Cepheus. It describes several giant molecular cloud complexes located at various distances from the Sun, ranging from clouds within 500 pc to regions associated with the Perseus spiral arm at 2-3 kpc. Key regions discussed include the Cepheus Flare clouds below 500 pc, three OB associations (Cep OB2, Cep OB3, Cep OB4) located 600-900 pc away, and the well-known high mass star forming region S 140 located at 900 pc. Tables list molecular clouds and young stars identified in the Cepheus region. Maps show the distribution of clouds, extinction, and pre-main sequence stars across Cepheus.
The document summarizes new Chandra and HST observations of the X-ray source IC 10 X-1 located in the nearby galaxy IC 10. The observations confirm that IC 10 X-1 has an average X-ray luminosity of 1.5 × 1038 erg s-1 and is strongly variable. The position of IC 10 X-1, within 0.23 arcseconds, matches the location of the Wolf-Rayet star [MAC92] 17A in IC 10. The observations suggest IC 10 X-1 may be a rare Wolf-Rayet black hole binary system, based on its luminosity, variability, and association with the Wolf-Rayet star.
Science laser altimetry of small scale features on 433 eros from near-shoemakerFelipe Correa
This article summarizes findings from laser altimetry observations of asteroid 433 Eros made by the NEAR spacecraft during its close flyby. The laser observations revealed surface features on scales of meters to hundreds of meters, showing that the surface has a fractal structure dominated by blocks, structural features, and small crater walls. This fractal structure suggests a single process, likely impacts, dominates the surface morphology on these scales. Laser altimetry also measured local surface elevations and slopes, correlating elevations with morphological evidence of downslope movement of loose surface materials.
Creation of cosmic structure in the complex galaxy cluster merger abell 2744Sérgio Sacani
Abell 2744 is one of the most actively merging galaxy clusters known, appearing to have "dark", "ghost", "bullet", and "stripped" substructures of around 1014 solar masses each. The cluster shows a complex phenomenology that will challenge simulations to reproduce. The authors present a detailed strong lensing, weak lensing, and X-ray analysis of Abell 2744, identifying 34 strongly lensed images around the massive Southern core and producing the most detailed mass map to date. They find evidence that the Southern core and Northwestern substructure are post-merger systems similar to the Bullet Cluster viewed from an angle, and derive a new constraint on the self-interaction cross section of dark matter particles. They
Rocket and fuse_observations_of_ic405_differential_extinction_and_fluorescent...Sérgio Sacani
The document describes rocket and FUSE observations of the emission/reflection nebula IC 405. The observations show that the ratio of nebular surface brightness to stellar flux (S/F*) increases by about two orders of magnitude towards the blue end of the far-UV bandpass. Scattering models fail to reproduce this "blue rise" effect. FUSE spectroscopy reveals a rich fluorescent molecular hydrogen spectrum north of the star. The observations suggest that uncertainties in nebular geometry and dust clumping are likely responsible for the blue rise, rather than fluorescent H2 emission. If IC 405 was spatially unresolved, it would appear to have less dust extinction than observed.
A herschel and_apex_census_of_the_reddest_sources_in_orion_searching_for_the_...Sérgio Sacani
This document summarizes a study that uses Herschel and APEX data to identify the reddest, youngest protostar candidates in the Orion molecular clouds. 55 new protostar candidates are detected at 70 and 160 microns that were too faint or undetected at 24 microns in previous Spitzer data. The 11 reddest candidates with log(70 micron flux / 24 micron flux) > 1.65 are considered reliable protostars, while the remaining 44 have less extreme colors and higher contamination potential. Combining these with previously known protostars yields 18 sources called PACS Bright Red sources (PBRs) with the reddest colors. Analysis finds the PBRs have properties of very young Class 0 sources like
This article discusses how growing season temperatures by the end of the 21st century will likely exceed the most extreme seasonal temperatures recorded from 1900 to 2006, especially in tropical and subtropical regions. Using output from 23 global climate models, the authors calculate there is over a 90% probability of this occurring. They argue this poses risks to global food security as extreme heat can significantly reduce agricultural productivity. The article examines historical examples of damage caused by extreme seasonal heat and argues these short-term events may become long-term trends without sufficient investments in adaptation.
Measurements of a_massive_galaxy_clusterSérgio Sacani
This document reports on observations of IDCS J1426.5+3508, a galaxy cluster located at a redshift of 1.75. A Sunyaev-Zeldovich decrement was detected towards this cluster, indicating a total mass of 4.3×1014 solar masses. This makes it the most distant cluster detected via the Sunyaev-Zeldovich effect to date and the most massive cluster found at a redshift greater than 1.4. Despite its rarity, the cluster is not unexpected given cosmological models and the large area surveyed. However, it remains one of the rarest and most extreme clusters discovered and provides insight into the early formation of the most massive clusters.
The panoramic view_on_the_recent_star_formation_in_ic2574Sérgio Sacani
This document summarizes research on star formation activity in the dwarf galaxy IC 2574 using deep imaging from the Large Binocular Telescope. The imaging is used to identify star-forming regions and construct maps of stellar age and mass surface density on sub-kiloparsec scales. The analysis finds an older burst of star formation occurred about 100 Myr ago within 4 kpc of the galaxy center, while a younger burst in the last 10 Myr occurred between 4-8 kpc. No correlation is seen between star formation and atomic hydrogen gas on local scales, suggesting star formation does not locally expel or ionize a significant fraction of hydrogen. The stellar populations in known hydrogen holes in IC 2574 are also analyzed, finding
This document appears to be a citation to a 1996 Astrophysical Journal paper with the volume number 458 and page number 600, but it provides no other contextual information about the content or findings of the cited paper. The summary is limited due to the lack of substantive information in the given document.
This document reports the detection of a low-mass dark satellite galaxy in a gravitational lens system. Using pixelated lens modeling of adaptive optics images, the researchers detected a positive density correction indicating the presence of a mass substructure. They estimate the mass of the substructure to be 1.9 x 108 solar masses located 600 parsecs from the density peak. Combining this detection with a previous one, they constrain the logarithmic slope of the mass function for dark matter substructure in elliptical galaxies to be 1.1-0.4 with an average mass fraction of 3.3-1.8%. This is consistent with predictions from cold dark matter simulations.
The study examines a post-starburst galaxy outflow using ultraviolet spectroscopy of multiple ions including hydrogen. It finds the outflow extends at least 160,000 light-years from the galaxy and contains a hidden mass of at least 6x10^9 times the mass of our Sun. This challenges previous assumptions about the extent and mass of galaxy outflows, suggesting they may play a larger role in regulating galaxy evolution than thought.
The document summarizes research on the South Pole-Aitken basin, the largest impact crater on the Moon. It is over 2,500 km in diameter and more than 12 km deep. Spacecraft data show the basin has a higher concentration of iron than surrounding lunar highlands, suggesting it may expose deeper mantle rocks. However, the exact composition is debated, with some researchers arguing mantle rocks are not present based on mineral analysis. Understanding the basin's composition could provide insights into the Moon's interior structure and composition from the impact that formed the giant crater.
This document summarizes long-slit spectroscopic observations of four planetary nebulae - Hb 4, IC 4634, NGC 6369, and NGC 7354 - conducted with the Palomar 5 m telescope. The observations were aimed at investigating the spectroscopic properties of microstructures like jets and FLIERs (fast, low-ionization emission regions) seen in these planetary nebulae. Physical conditions and chemical abundances were derived from emission line ratios along the structural axes of the microstructures. In most cases, no evidence of shock activity or nitrogen-to-oxygen abundance anomalies was found, unlike some previous studies of similar structures. Microstructures appear to be a heterogeneous class of structures aside from their generally supersonic
1) NGC 474 is a lenticular galaxy surrounded by shells of matter whose origin is still debated - they could have formed from merging with a low mass galaxy or gravitational interaction with satellite galaxy NGC 470.
2) Photometric analysis of NGC 474 found its surface brightness profile is typical for a lenticular galaxy even in the center, and the color indices of the shells are consistent with NGC 474.
3) This implies the shells most likely originated from gravitational interaction with NGC 470 rather than from merging, as merging would have disturbed the central surface brightness profile.
This document summarizes a study that used optical, infrared, and submillimeter data to examine star formation in the region surrounding the IC 348 star cluster and the nearby Flying Ghost Nebula. The study identified 13 protostars driving protostellar outflows in the region, including HH 211 which had not previously been detected at visible wavelengths. The region surrounding the Flying Ghost Nebula shows ongoing star formation with outflows similar to other areas of moderate star formation in Perseus. A candidate bent jet was also found, which may have been ejected from a multiple star system near IC 348.
The discovery of a giant arc associated with the galaxy cluster IDCS J1426.5+3508 at z=1.75 is reported. HST imaging reveals an arc-like object with a length-to-width ratio greater than 10, located near the brightest cluster galaxy. Attempts to measure the redshift of the arc through spectroscopy were unsuccessful. The existence of such a massive, strongly lensing cluster at this early epoch poses challenges for the standard ΛCDM model of structure formation.
Type iax supernovae_a_new_class_of_stellar_explosionSérgio Sacani
Type Iax supernovae are a new class of stellar explosions that are spectroscopically similar to Type Ia supernovae but have lower maximum light velocities and peak magnitudes. They typically have lower ejecta masses and hotter photospheres than Type Ia. The progenitor system is likely a carbon-oxygen white dwarf that accretes matter from a helium star companion, resulting in a deflagration explosion that does not fully disrupt the white dwarf. Type Iax events occur about 31 times as frequently as Type Ia supernovae.
This document summarizes the results of a study using Herschel Space Observatory data to analyze the physical properties of dust in the RCW 120 H ii region. The study finds:
1) Dust temperatures in RCW 120 range from around 30 K in the interior decreasing to 20 K in the photo-dissociation region and 10 K in nearby infrared dark clouds.
2) There is tentative evidence of an anti-correlation between dust temperature and the dust emissivity index β, with cooler dust having higher β values, consistent with some previous studies.
3) RCW 120 appears to be in the process of destroying its photo-dissociation region boundary and leaked radiation from the interior may be influencing the
This document summarizes the discovery of a stellar tidal stream around the nearby dwarf galaxy NGC 4449 using deep imaging. The stream implies a massive dwarf spheroidal progenitor that is disrupting and depositing stars into NGC 4449's halo. The luminosity ratio between the two galaxies is around 1:50, but their dynamical mass ratio including dark matter may be 1:10-1:5. This "stealth merger" suggests that satellite accretion can significantly build up stellar halos of low-mass galaxies and possibly trigger their starbursts.
This study uses deep Chandra observations to examine the X-ray morphology of the circum-nuclear region of NGC 4151 on spatial scales down to 30 pc. Extended soft X-ray emission is detected out to 1.3 kpc from the nucleus, farther than seen in previous studies. The X-ray emission is more absorbed towards the boundaries of the ionization cone and perpendicular to the bicone, suggesting absorption by a torus. The innermost X-ray emission, coincident with H2 emission and dusty spirals, supports X-ray excitation of molecular gas. The extended X-ray emission may be due to hot gas heated by the AGN outflow or photoionized by past AGN activity.
This document summarizes star forming regions in the constellation of Cepheus. It describes several giant molecular cloud complexes located at various distances from the Sun, ranging from clouds within 500 pc to regions associated with the Perseus spiral arm at 2-3 kpc. Key regions discussed include the Cepheus Flare clouds below 500 pc, three OB associations (Cep OB2, Cep OB3, Cep OB4) located 600-900 pc away, and the well-known high mass star forming region S 140 located at 900 pc. Tables list molecular clouds and young stars identified in the Cepheus region. Maps show the distribution of clouds, extinction, and pre-main sequence stars across Cepheus.
The document summarizes new Chandra and HST observations of the X-ray source IC 10 X-1 located in the nearby galaxy IC 10. The observations confirm that IC 10 X-1 has an average X-ray luminosity of 1.5 × 1038 erg s-1 and is strongly variable. The position of IC 10 X-1, within 0.23 arcseconds, matches the location of the Wolf-Rayet star [MAC92] 17A in IC 10. The observations suggest IC 10 X-1 may be a rare Wolf-Rayet black hole binary system, based on its luminosity, variability, and association with the Wolf-Rayet star.
Science laser altimetry of small scale features on 433 eros from near-shoemakerFelipe Correa
This article summarizes findings from laser altimetry observations of asteroid 433 Eros made by the NEAR spacecraft during its close flyby. The laser observations revealed surface features on scales of meters to hundreds of meters, showing that the surface has a fractal structure dominated by blocks, structural features, and small crater walls. This fractal structure suggests a single process, likely impacts, dominates the surface morphology on these scales. Laser altimetry also measured local surface elevations and slopes, correlating elevations with morphological evidence of downslope movement of loose surface materials.
Creation of cosmic structure in the complex galaxy cluster merger abell 2744Sérgio Sacani
Abell 2744 is one of the most actively merging galaxy clusters known, appearing to have "dark", "ghost", "bullet", and "stripped" substructures of around 1014 solar masses each. The cluster shows a complex phenomenology that will challenge simulations to reproduce. The authors present a detailed strong lensing, weak lensing, and X-ray analysis of Abell 2744, identifying 34 strongly lensed images around the massive Southern core and producing the most detailed mass map to date. They find evidence that the Southern core and Northwestern substructure are post-merger systems similar to the Bullet Cluster viewed from an angle, and derive a new constraint on the self-interaction cross section of dark matter particles. They
Rocket and fuse_observations_of_ic405_differential_extinction_and_fluorescent...Sérgio Sacani
The document describes rocket and FUSE observations of the emission/reflection nebula IC 405. The observations show that the ratio of nebular surface brightness to stellar flux (S/F*) increases by about two orders of magnitude towards the blue end of the far-UV bandpass. Scattering models fail to reproduce this "blue rise" effect. FUSE spectroscopy reveals a rich fluorescent molecular hydrogen spectrum north of the star. The observations suggest that uncertainties in nebular geometry and dust clumping are likely responsible for the blue rise, rather than fluorescent H2 emission. If IC 405 was spatially unresolved, it would appear to have less dust extinction than observed.
A herschel and_apex_census_of_the_reddest_sources_in_orion_searching_for_the_...Sérgio Sacani
This document summarizes a study that uses Herschel and APEX data to identify the reddest, youngest protostar candidates in the Orion molecular clouds. 55 new protostar candidates are detected at 70 and 160 microns that were too faint or undetected at 24 microns in previous Spitzer data. The 11 reddest candidates with log(70 micron flux / 24 micron flux) > 1.65 are considered reliable protostars, while the remaining 44 have less extreme colors and higher contamination potential. Combining these with previously known protostars yields 18 sources called PACS Bright Red sources (PBRs) with the reddest colors. Analysis finds the PBRs have properties of very young Class 0 sources like
This article discusses how growing season temperatures by the end of the 21st century will likely exceed the most extreme seasonal temperatures recorded from 1900 to 2006, especially in tropical and subtropical regions. Using output from 23 global climate models, the authors calculate there is over a 90% probability of this occurring. They argue this poses risks to global food security as extreme heat can significantly reduce agricultural productivity. The article examines historical examples of damage caused by extreme seasonal heat and argues these short-term events may become long-term trends without sufficient investments in adaptation.
Measurements of a_massive_galaxy_clusterSérgio Sacani
This document reports on observations of IDCS J1426.5+3508, a galaxy cluster located at a redshift of 1.75. A Sunyaev-Zeldovich decrement was detected towards this cluster, indicating a total mass of 4.3×1014 solar masses. This makes it the most distant cluster detected via the Sunyaev-Zeldovich effect to date and the most massive cluster found at a redshift greater than 1.4. Despite its rarity, the cluster is not unexpected given cosmological models and the large area surveyed. However, it remains one of the rarest and most extreme clusters discovered and provides insight into the early formation of the most massive clusters.
The panoramic view_on_the_recent_star_formation_in_ic2574Sérgio Sacani
This document summarizes research on star formation activity in the dwarf galaxy IC 2574 using deep imaging from the Large Binocular Telescope. The imaging is used to identify star-forming regions and construct maps of stellar age and mass surface density on sub-kiloparsec scales. The analysis finds an older burst of star formation occurred about 100 Myr ago within 4 kpc of the galaxy center, while a younger burst in the last 10 Myr occurred between 4-8 kpc. No correlation is seen between star formation and atomic hydrogen gas on local scales, suggesting star formation does not locally expel or ionize a significant fraction of hydrogen. The stellar populations in known hydrogen holes in IC 2574 are also analyzed, finding
This document appears to be a citation to a 1996 Astrophysical Journal paper with the volume number 458 and page number 600, but it provides no other contextual information about the content or findings of the cited paper. The summary is limited due to the lack of substantive information in the given document.
This document reports the detection of a low-mass dark satellite galaxy in a gravitational lens system. Using pixelated lens modeling of adaptive optics images, the researchers detected a positive density correction indicating the presence of a mass substructure. They estimate the mass of the substructure to be 1.9 x 108 solar masses located 600 parsecs from the density peak. Combining this detection with a previous one, they constrain the logarithmic slope of the mass function for dark matter substructure in elliptical galaxies to be 1.1-0.4 with an average mass fraction of 3.3-1.8%. This is consistent with predictions from cold dark matter simulations.
The study examines a post-starburst galaxy outflow using ultraviolet spectroscopy of multiple ions including hydrogen. It finds the outflow extends at least 160,000 light-years from the galaxy and contains a hidden mass of at least 6x10^9 times the mass of our Sun. This challenges previous assumptions about the extent and mass of galaxy outflows, suggesting they may play a larger role in regulating galaxy evolution than thought.
The document summarizes research on the South Pole-Aitken basin, the largest impact crater on the Moon. It is over 2,500 km in diameter and more than 12 km deep. Spacecraft data show the basin has a higher concentration of iron than surrounding lunar highlands, suggesting it may expose deeper mantle rocks. However, the exact composition is debated, with some researchers arguing mantle rocks are not present based on mineral analysis. Understanding the basin's composition could provide insights into the Moon's interior structure and composition from the impact that formed the giant crater.
This article reports the detection of two gas clouds with no discernible elements heavier than hydrogen, representing the lowest heavy-element abundance observed in the early universe. One cloud at z=3.4 exhibits a deuterium abundance matching predictions from Big Bang nucleosynthesis, providing direct evidence for the standard cosmological model. The sparse metal enrichment of these clouds implies an inhomogeneous process for transporting heavy elements from galaxies into the surrounding intergalactic medium.
1) Newly-born pulsars offer favorable conditions for accelerating heavy nuclei like iron to ultrahigh energies via unipolar induction. However, these nuclei must escape the surrounding dense supernova envelope.
2) The paper analytically and numerically examines the escape of ultrahigh energy cosmic rays (UHECRs) from supernova envelopes. It finds that at early times when protons could reach energies above 10^20 eV, the envelope prevents their escape. However, heavier iron nuclei can still reach the highest observed energies at later times when the envelope has thinned.
3) The authors conclude that a small fraction (0.01%) of extragalactic rapidly rotating young pulsars embedded in supernov
The document discusses the training that Apollo astronauts received for making observations and taking photographs from lunar orbit. It summarizes that (1) astronauts were trained to add to scientific knowledge by describing lunar features from their unique viewpoint in orbit, and (2) photographs from orbit could provide regional context for detailed surface exploration findings. The training grew over missions from briefings to extensive classroom sessions. Outstanding results from astronaut observations and photos included realizing limitations of depicting lunar surface colors photographically and discovering previously unknown farside features.
This document summarizes VLBI observations of supernova SN 2011dh made 14 days after its discovery, providing the earliest radio image of a supernova. The observations detected SN 2011dh at 22 GHz using a subset of the EVN array. The recovered flux density was approximately half the value measured by the EVLA at the same frequency and epoch, possibly due to extended emission or calibration issues. Precise coordinates for SN 2011dh were determined, linked to the ICRF, which may help improve future VLBI observations of the supernova.
This document summarizes the discovery of a luminous quasar (ULAS J112001.481064124.3) with a redshift of z=7.085, located approximately 777 million years after the Big Bang. It has a luminosity of 6.3 x 10^13 solar luminosities and hosts a black hole with a mass of 2 x 10^9 solar masses. The radius of its ionized region is 1.9 megaparsecs, smaller than typical quasars from z=6.0 to z=6.4. Analysis of its spectrum is consistent with a high neutral fraction (>0.1) of the intergalactic medium in front of it. This makes it the most
A 100 parsec elliptical and twisted ring of cold and dense molecular clouds r...Sérgio Sacani
The document summarizes observations from the Herschel satellite that reveal a 100-parsec elliptical and twisted ring of cold, dense molecular clouds orbiting the Galactic Center. The ring has a mass of about 3 million solar masses and semi-major axes of 100 and 60 parsecs. Its major axis is inclined 40 degrees to the plane of the sky and perpendicular to the Galactic Bar. The ring appears to trace stable x2 orbits predicted for the barred Galactic potential.
First detection of_molecular_gas_in_shells_in_cena_galaxySérgio Sacani
This document reports the first detection of molecular gas (CO) in the shells of the galaxy Centaurus A (Cen A), located 15 kpc from the galaxy's center. The ratio of CO to HI emission in the shells matches what is found in the galaxy's central regions, which is unexpected given typical metallicity gradients in galaxies. The detection of molecular gas in the shells provides evidence that molecular gas in galaxy mergers may be spread further from nuclear regions than previously thought. The dynamics of the gas can be understood if the interstellar medium is considered clumpy and less dissipative than assumed, allowing dense gas to orbit with stars and form shells.
Investigating the nuclear_activity_of_ngc1672Sérgio Sacani
1) The document investigates the nuclear activity of the barred spiral galaxy NGC 1672 using X-ray data from Chandra and XMM-Newton, as well as optical data from Hubble and infrared data from Spitzer.
2) It detects 28 X-ray sources within NGC 1672, with nine being ultraluminous X-ray sources located at the ends of the galaxy's bar.
3) For the first time, it shows NGC 1672 possesses a hard nuclear X-ray source surrounded by an X-ray bright circumnuclear star-forming ring, which dominates the central X-ray emission of the galaxy. The data indicates the nuclear source is a low-luminosity active gal
The fornax deep_survey_with_vst_i_the_extended_and_diffuse_stellar_halo_of_ng...Sérgio Sacani
We have started a new deep, multi-imaging survey of the Fornax cluster, dubbed Fornax Deep
Survey (FDS), at the VLT Survey Telescope. In this paper we present the deep photometry inside
two square degrees around the bright galaxy NGC 1399 in the core of the cluster. We found that
the core of the Fornax cluster is characterised by a very extended and diffuse envelope surrounding
the luminous galaxy NGC 1399: we map the surface brightness out to 33 arcmin (∼ 192 kpc)
from the galaxy center and down to μg ∼ 31 mag arcsec−2 in the g band. The deep photometry
allows us to detect a faint stellar bridge in the intracluster region on the west side of NGC 1399
and towards NGC 1387. By analyzing the integrated colors of this feature, we argue that it
could be due to the ongoing interaction between the two galaxies, where the outer envelope of
NGC 1387 on its east side is stripped away. By fitting the light profile, we found that exists a
physical break radius in the total light distribution at R = 10 arcmin (∼ 58 kpc) that sets the
transition region between the bright central galaxy and the outer exponential halo, and that the
stellar halo contributes for 60% of the total light of the galaxy (Sec. 3.5). We discuss the main
implications of this work on the build-up of the stellar halo at the center of the Fornax cluster.
By comparing with the numerical simulations of the stellar halo formation for the most massive
BCGs (i.e. 13 < logM200/M⊙ < 14), we find that the observed stellar halo mass fraction is
consistent with a halo formed through the multiple accretion of progenitors with stellar mass in
the range 108 − 1011 M⊙. This might suggest that the halo of NGC 1399 has also gone through
a major merging event. The absence of a significant number of luminous stellar streams and
tidal tails out to 192 kpc suggests that the epoch of this strong interaction goes back to an early
formation epoch. Therefore, differently from the Virgo cluster, the extended stellar halo around
NGC 1399 is characterised by a more diffuse and well-mixed component, including the ICL.
This document summarizes an infrared survey of the massive star forming region RCW 57 (NGC 3576) using L-band (3.5 μm) data from SPIREX and JHKs data from 2MASS. Over 50% of the 209 sources detected showed infrared excess, indicating circumstellar disks. Comparison to other surveys supports a very high initial disk fraction (>80%) around massive stars, though disks may dissipate faster around high-mass stars. 33 sources only detected at L-band indicate heavily embedded, massive Class I protostars. Diffuse PAH emission was also detected throughout RCW 57.
Rings in the_haloes_of_planetary_nebulaeSérgio Sacani
This document presents the discovery of ring structures in the haloes of eight planetary nebulae, tripling the number known to have such rings. The rings are analyzed using image processing techniques to enhance their visibility. They find ring spacings range from less than 0.01 pc to 0.06 pc. This suggests ring spacing increases with time after the asymptotic giant branch phase. The properties of the rings support predictions of dust-driven wind instability models of mass loss but do not rule out other models. Analyzing the new detections provides insights into mass modulation processes late in stellar evolution.
This document summarizes a survey of the massive star forming region RCW 57 (NGC 3576) using JHKs and L-band (3.5 μm) infrared data. Over 50% of the sources detected showed infrared excess emission, indicating the presence of circumstellar disks. Comparison to other regions supported a very high initial disk fraction (>80%) around massive stars, though disks may dissipate faster around high-mass stars. 33 sources only detected at L-band indicated heavily embedded, massive Class I protostars. Diffuse polycyclic aromatic hydrocarbon emission was also detected throughout the region.
This document summarizes Herschel observations of the Fornax galaxy cluster at 100, 160, 250, 350, and 500 μm. It identifies 11 bright galaxies detected at 500 μm that can be compared to previous observations of galaxies in the Virgo cluster. Stellar and far-infrared luminosities are calculated for each galaxy, and modified blackbody curves are fit to derive dust masses and temperatures. The dust properties of Fornax galaxies are found to be broadly similar to those of Virgo galaxies. Fornax shows higher far-infrared luminosity density but lower gas density than Virgo, indicating gas loss in the cluster environment.
1) The EPOXI mission flew by comet Hartley 2 in 2010, obtaining over 105 images and spectra.
2) Hartley 2 has an unusually small but very active bi-lobed nucleus with dimensions of 2.33 km and a rotation period of about 18 hours.
3) The nucleus shows substantial differences in volatile composition between its lobes and waist region.
A young protoplanet_candidate_embedded_in_the_circumstellar_disk_of_hd100546Sérgio Sacani
This document summarizes observations of HD100546 using high-contrast imaging techniques. A faint emission source was detected near the star at a projected separation of about 47 AU. The position of the source coincides with a deficit in polarization observed from the circumstellar disk. This suggests a physical link between the source and the disk. Considering various scenarios, the authors favor interpreting the source as a young protoplanet currently forming within the disk. Follow-up observations could distinguish between different possible explanations for the observed features. If confirmed, it would be a unique opportunity to study giant planet formation within an optically thick disk.
Searching for signs_of_triggered_star_formation_toward_ic1848Sérgio Sacani
This document summarizes observations of three bright-rimmed clouds - SFO 11, SFO 11NE, and SFO 11E - associated with the HII region IC 1848, using submillimeter continuum data from SCUBA on the JCMT and molecular line data from CO isotopologues. The observations show evidence for protostellar cores within the clouds and recent or ongoing star formation. Based on the morphology and pressures inferred from the data, it is possible the UV illumination from the primary ionizing star HD17505 has triggered the collapse of dense molecular cores within SFO 11 and SFO 11E.
This document summarizes a study that uses cosmological simulations to model the formation of stellar halos around galaxies via the tidal disruption of accreted dwarf galaxies. The simulations follow the dynamical evolution and disruption of satellites from high redshift in a fully cosmological setting. The simulations produce stellar halos with masses and density profiles consistent with observations of the Milky Way and M31. The stellar halos show complex structures composed of well-mixed components, tidal streams, shells, and other substructures rather than smooth distributions.
An infrared proper_motion_study_of_bullets_of_orion_nebulaSérgio Sacani
This study measured the proper motions of infrared-emitting bullets in the Orion Nebula using images taken with a four-year time baseline. The [Fe II]-emitting bullets were found to be moving at around 170 km/s, while H2 bullets had smaller motions. Differential motion was not observed between [Fe II] bullets and trailing H2 wakes, suggesting they have reached a steady configuration over at least 100 years. The proper motions provide constraints on the origin and dynamics of the bullet systems, with an impulsive origin appearing likely.
This document summarizes a study of the outer rings of supernova SN 1987A using spectroscopy and archival Hubble Space Telescope images spanning 11 years. The study finds:
1) Light curves of emission lines from the outer rings show a declining behavior, consistent with initial supernova flash powering.
2) Electron densities in the outer rings are <3,000 cm-3 and have not changed in 15 years. Temperature remains at ~12,000 K.
3) Densities may be highest (~5,000 cm-3) in the southern outer ring, which shows slightly faster decline in H-alpha emission.
4) Interaction between supernova ejecta and outer rings could begin within ~
A multiband study_of_hercules_a_ii_multifrequency_vlaSérgio Sacani
This document summarizes a multi-frequency study of the radio galaxy Hercules A using the VLA radio telescope. The observations revealed that the bright jets and prominent rings have a flatter spectrum than the surrounding lobes and bridge, suggesting they represent a recent outburst from the active nucleus. The magnetic field closely follows the edges of the lobes, jets, and rings. There is also an asymmetry in the spectral properties between the two lobes that can be explained by relativistic beaming and light travel delays.
1. VFTS 682 is a very massive star located 29 pc in projection from the young massive cluster R136 in the Tarantula Nebula of the LMC.
2. Spectral modeling finds it has an unusually high luminosity of log(L/L) = 6.5, corresponding to a present-day mass of ~150 solar masses.
3. Its isolation and mass pose the question of whether it formed in situ, which would profoundly impact theories of massive star formation, or if it was ejected from R136, making it the most massive runaway star known.
This document introduces the VLT-FLAMES Tarantula Survey, which obtained multi-epoch optical spectroscopy of over 800 massive stars in the 30 Doradus region of the Large Magellanic Cloud. The survey aims to detect massive binary systems through variations in radial velocities and to characterize the properties of O- and B-type stars, addressing questions about stellar and cluster evolution. Spectral classifications are provided for newly discovered emission-line stars, including a new Wolf-Rayet star. The survey data and reduction procedures are overviewed, and upcoming analyses of the massive star properties are announced.
This document summarizes the results of a deep near-infrared survey of the Carina Nebula complex using the HAWK-I instrument on the VLT. The survey imaged an area of 0.36 square degrees down to magnitudes of J=23, H=22, and Ks=21, detecting over 600,000 infrared sources. Color-magnitude diagrams of the sources were analyzed to determine properties of the low-mass stellar population such as ages and masses. The survey found that about 3200 sources have masses above 1 solar mass, consistent with expectations from the initial mass function. It also found that about half of the young stars in Carina are in a widely distributed, non-clustered configuration. Six
This paper presents a study of the extended X-ray emission in the Seyfert galaxy NGC 4151 using deep Chandra observations. Key findings include:
1) Emission line maps show strong OVII, OVIII, and NeIX line emission extending along the northeast-southwest direction, consistent with an ionization cone.
2) Spectral analysis finds the extended emission is well described by photoionized plasma models, supporting a dominant role for nuclear photoionization.
3) Faint extended emission is also seen perpendicular to the ionization cone, indicating some leakage of nuclear ionizing radiation through warm absorbers rather than being blocked by an obscuring torus.
This document presents a spectroscopic analysis of low-ionization structures (LISs) in five planetary nebulae to study their physical, kinematic, and excitation properties. The analysis finds that LISs and other nebular components have similar electron temperatures, while the electron density is systematically lower in LISs. Chemical abundances do not differ significantly between components. Diagnostic diagrams indicate LISs are mainly excited by shocks, while other components are photoionized. New diagnostic diagrams involving emission lines and the ionization flux ratio suggest shock excitation dominates where log(fshocks/f) > -1 and photoionization where log(fshocks/f) < -2, with a transition zone
Similar to Characterizing interstellar filaments with herschel in ic5146 (20)
The binding of cosmological structures by massless topological defectsSérgio Sacani
Assuming spherical symmetry and weak field, it is shown that if one solves the Poisson equation or the Einstein field
equations sourced by a topological defect, i.e. a singularity of a very specific form, the result is a localized gravitational
field capable of driving flat rotation (i.e. Keplerian circular orbits at a constant speed for all radii) of test masses on a thin
spherical shell without any underlying mass. Moreover, a large-scale structure which exploits this solution by assembling
concentrically a number of such topological defects can establish a flat stellar or galactic rotation curve, and can also deflect
light in the same manner as an equipotential (isothermal) sphere. Thus, the need for dark matter or modified gravity theory is
mitigated, at least in part.
EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Weste...Sérgio Sacani
Context. With a mass exceeding several 104 M⊙ and a rich and dense population of massive stars, supermassive young star clusters
represent the most massive star-forming environment that is dominated by the feedback from massive stars and gravitational interactions
among stars.
Aims. In this paper we present the Extended Westerlund 1 and 2 Open Clusters Survey (EWOCS) project, which aims to investigate
the influence of the starburst environment on the formation of stars and planets, and on the evolution of both low and high mass stars.
The primary targets of this project are Westerlund 1 and 2, the closest supermassive star clusters to the Sun.
Methods. The project is based primarily on recent observations conducted with the Chandra and JWST observatories. Specifically,
the Chandra survey of Westerlund 1 consists of 36 new ACIS-I observations, nearly co-pointed, for a total exposure time of 1 Msec.
Additionally, we included 8 archival Chandra/ACIS-S observations. This paper presents the resulting catalog of X-ray sources within
and around Westerlund 1. Sources were detected by combining various existing methods, and photon extraction and source validation
were carried out using the ACIS-Extract software.
Results. The EWOCS X-ray catalog comprises 5963 validated sources out of the 9420 initially provided to ACIS-Extract, reaching a
photon flux threshold of approximately 2 × 10−8 photons cm−2
s
−1
. The X-ray sources exhibit a highly concentrated spatial distribution,
with 1075 sources located within the central 1 arcmin. We have successfully detected X-ray emissions from 126 out of the 166 known
massive stars of the cluster, and we have collected over 71 000 photons from the magnetar CXO J164710.20-455217.
The debris of the ‘last major merger’ is dynamically youngSérgio Sacani
The Milky Way’s (MW) inner stellar halo contains an [Fe/H]-rich component with highly eccentric orbits, often referred to as the
‘last major merger.’ Hypotheses for the origin of this component include Gaia-Sausage/Enceladus (GSE), where the progenitor
collided with the MW proto-disc 8–11 Gyr ago, and the Virgo Radial Merger (VRM), where the progenitor collided with the
MW disc within the last 3 Gyr. These two scenarios make different predictions about observable structure in local phase space,
because the morphology of debris depends on how long it has had to phase mix. The recently identified phase-space folds in Gaia
DR3 have positive caustic velocities, making them fundamentally different than the phase-mixed chevrons found in simulations
at late times. Roughly 20 per cent of the stars in the prograde local stellar halo are associated with the observed caustics. Based
on a simple phase-mixing model, the observed number of caustics are consistent with a merger that occurred 1–2 Gyr ago.
We also compare the observed phase-space distribution to FIRE-2 Latte simulations of GSE-like mergers, using a quantitative
measurement of phase mixing (2D causticality). The observed local phase-space distribution best matches the simulated data
1–2 Gyr after collision, and certainly not later than 3 Gyr. This is further evidence that the progenitor of the ‘last major merger’
did not collide with the MW proto-disc at early times, as is thought for the GSE, but instead collided with the MW disc within
the last few Gyr, consistent with the body of work surrounding the VRM.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
Multi-source connectivity as the driver of solar wind variability in the heli...Sérgio Sacani
The ambient solar wind that flls the heliosphere originates from multiple
sources in the solar corona and is highly structured. It is often described
as high-speed, relatively homogeneous, plasma streams from coronal
holes and slow-speed, highly variable, streams whose source regions are
under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify
solar wind sources and understand what drives the complexity seen in the
heliosphere. By combining magnetic feld modelling and spectroscopic
techniques with high-resolution observations and measurements, we show
that the solar wind variability detected in situ by Solar Orbiter in March
2022 is driven by spatio-temporal changes in the magnetic connectivity to
multiple sources in the solar atmosphere. The magnetic feld footpoints
connected to the spacecraft moved from the boundaries of a coronal hole
to one active region (12961) and then across to another region (12957). This
is refected in the in situ measurements, which show the transition from fast
to highly Alfvénic then to slow solar wind that is disrupted by the arrival of
a coronal mass ejection. Our results describe solar wind variability at 0.5 au
but are applicable to near-Earth observatories.
Gliese 12 b: A Temperate Earth-sized Planet at 12 pc Ideal for Atmospheric Tr...Sérgio Sacani
Recent discoveries of Earth-sized planets transiting nearby M dwarfs have made it possible to characterize the
atmospheres of terrestrial planets via follow-up spectroscopic observations. However, the number of such planets
receiving low insolation is still small, limiting our ability to understand the diversity of the atmospheric
composition and climates of temperate terrestrial planets. We report the discovery of an Earth-sized planet
transiting the nearby (12 pc) inactive M3.0 dwarf Gliese 12 (TOI-6251) with an orbital period (Porb) of 12.76 days.
The planet, Gliese 12 b, was initially identified as a candidate with an ambiguous Porb from TESS data. We
confirmed the transit signal and Porb using ground-based photometry with MuSCAT2 and MuSCAT3, and
validated the planetary nature of the signal using high-resolution images from Gemini/NIRI and Keck/NIRC2 as
well as radial velocity (RV) measurements from the InfraRed Doppler instrument on the Subaru 8.2 m telescope
and from CARMENES on the CAHA 3.5 m telescope. X-ray observations with XMM-Newton showed the host
star is inactive, with an X-ray-to-bolometric luminosity ratio of log 5.7 L L X bol » - . Joint analysis of the light
curves and RV measurements revealed that Gliese 12 b has a radius of 0.96 ± 0.05 R⊕,a3σ mass upper limit of
3.9 M⊕, and an equilibrium temperature of 315 ± 6 K assuming zero albedo. The transmission spectroscopy metric
(TSM) value of Gliese 12 b is close to the TSM values of the TRAPPIST-1 planets, adding Gliese 12 b to the small
list of potentially terrestrial, temperate planets amenable to atmospheric characterization with JWST.
Gliese 12 b, a temperate Earth-sized planet at 12 parsecs discovered with TES...Sérgio Sacani
We report on the discovery of Gliese 12 b, the nearest transiting temperate, Earth-sized planet found to date. Gliese 12 is a
bright (V = 12.6 mag, K = 7.8 mag) metal-poor M4V star only 12.162 ± 0.005 pc away from the Solar system with one of the
lowest stellar activity levels known for M-dwarfs. A planet candidate was detected by TESS based on only 3 transits in sectors
42, 43, and 57, with an ambiguity in the orbital period due to observational gaps. We performed follow-up transit observations
with CHEOPS and ground-based photometry with MINERVA-Australis, SPECULOOS, and Purple Mountain Observatory,
as well as further TESS observations in sector 70. We statistically validate Gliese 12 b as a planet with an orbital period of
12.76144 ± 0.00006 d and a radius of 1.0 ± 0.1 R⊕, resulting in an equilibrium temperature of ∼315 K. Gliese 12 b has excellent
future prospects for precise mass measurement, which may inform how planetary internal structure is affected by the stellar
compositional environment. Gliese 12 b also represents one of the best targets to study whether Earth-like planets orbiting cool
stars can retain their atmospheres, a crucial step to advance our understanding of habitability on Earth and across the galaxy.
The importance of continents, oceans and plate tectonics for the evolution of...Sérgio Sacani
Within the uncertainties of involved astronomical and biological parameters, the Drake Equation
typically predicts that there should be many exoplanets in our galaxy hosting active, communicative
civilizations (ACCs). These optimistic calculations are however not supported by evidence, which is
often referred to as the Fermi Paradox. Here, we elaborate on this long-standing enigma by showing
the importance of planetary tectonic style for biological evolution. We summarize growing evidence
that a prolonged transition from Mesoproterozoic active single lid tectonics (1.6 to 1.0 Ga) to modern
plate tectonics occurred in the Neoproterozoic Era (1.0 to 0.541 Ga), which dramatically accelerated
emergence and evolution of complex species. We further suggest that both continents and oceans
are required for ACCs because early evolution of simple life must happen in water but late evolution
of advanced life capable of creating technology must happen on land. We resolve the Fermi Paradox
(1) by adding two additional terms to the Drake Equation: foc
(the fraction of habitable exoplanets
with significant continents and oceans) and fpt
(the fraction of habitable exoplanets with significant
continents and oceans that have had plate tectonics operating for at least 0.5 Ga); and (2) by
demonstrating that the product of foc
and fpt
is very small (< 0.00003–0.002). We propose that the lack
of evidence for ACCs reflects the scarcity of long-lived plate tectonics and/or continents and oceans on
exoplanets with primitive life.
A Giant Impact Origin for the First Subduction on EarthSérgio Sacani
Hadean zircons provide a potential record of Earth's earliest subduction 4.3 billion years ago. Itremains enigmatic how subduction could be initiated so soon after the presumably Moon‐forming giant impact(MGI). Earlier studies found an increase in Earth's core‐mantle boundary (CMB) temperature due to theaccumulation of the impactor's core, and our recent work shows Earth's lower mantle remains largely solid, withsome of the impactor's mantle potentially surviving as the large low‐shear velocity provinces (LLSVPs). Here,we show that a hot post‐impact CMB drives the initiation of strong mantle plumes that can induce subductioninitiation ∼200 Myr after the MGI. 2D and 3D thermomechanical computations show that a high CMBtemperature is the primary factor triggering early subduction, with enrichment of heat‐producing elements inLLSVPs as another potential factor. The models link the earliest subduction to the MGI with implications forunderstanding the diverse tectonic regimes of rocky planets.
Climate extremes likely to drive land mammal extinction during next supercont...Sérgio Sacani
Mammals have dominated Earth for approximately 55 Myr thanks to their
adaptations and resilience to warming and cooling during the Cenozoic. All
life will eventually perish in a runaway greenhouse once absorbed solar
radiation exceeds the emission of thermal radiation in several billions of
years. However, conditions rendering the Earth naturally inhospitable to
mammals may develop sooner because of long-term processes linked to
plate tectonics (short-term perturbations are not considered here). In
~250 Myr, all continents will converge to form Earth’s next supercontinent,
Pangea Ultima. A natural consequence of the creation and decay of Pangea
Ultima will be extremes in pCO2 due to changes in volcanic rifting and
outgassing. Here we show that increased pCO2, solar energy (F⨀;
approximately +2.5% W m−2 greater than today) and continentality (larger
range in temperatures away from the ocean) lead to increasing warming
hostile to mammalian life. We assess their impact on mammalian
physiological limits (dry bulb, wet bulb and Humidex heat stress indicators)
as well as a planetary habitability index. Given mammals’ continued survival,
predicted background pCO2 levels of 410–816 ppm combined with increased
F⨀ will probably lead to a climate tipping point and their mass extinction.
The results also highlight how global landmass configuration, pCO2 and F⨀
play a critical role in planetary habitability.
Constraints on Neutrino Natal Kicks from Black-Hole Binary VFTS 243Sérgio Sacani
The recently reported observation of VFTS 243 is the first example of a massive black-hole binary
system with negligible binary interaction following black-hole formation. The black-hole mass (≈10M⊙)
and near-circular orbit (e ≈ 0.02) of VFTS 243 suggest that the progenitor star experienced complete
collapse, with energy-momentum being lost predominantly through neutrinos. VFTS 243 enables us to
constrain the natal kick and neutrino-emission asymmetry during black-hole formation. At 68% confidence
level, the natal kick velocity (mass decrement) is ≲10 km=s (≲1.0M⊙), with a full probability distribution
that peaks when ≈0.3M⊙ were ejected, presumably in neutrinos, and the black hole experienced a natal
kick of 4 km=s. The neutrino-emission asymmetry is ≲4%, with best fit values of ∼0–0.2%. Such a small
neutrino natal kick accompanying black-hole formation is in agreement with theoretical predictions.
Detectability of Solar Panels as a TechnosignatureSérgio Sacani
In this work, we assess the potential detectability of solar panels made of silicon on an Earth-like
exoplanet as a potential technosignature. Silicon-based photovoltaic cells have high reflectance in the
UV-VIS and in the near-IR, within the wavelength range of a space-based flagship mission concept
like the Habitable Worlds Observatory (HWO). Assuming that only solar energy is used to provide
the 2022 human energy needs with a land cover of ∼ 2.4%, and projecting the future energy demand
assuming various growth-rate scenarios, we assess the detectability with an 8 m HWO-like telescope.
Assuming the most favorable viewing orientation, and focusing on the strong absorption edge in the
ultraviolet-to-visible (0.34 − 0.52 µm), we find that several 100s of hours of observation time is needed
to reach a SNR of 5 for an Earth-like planet around a Sun-like star at 10pc, even with a solar panel
coverage of ∼ 23% land coverage of a future Earth. We discuss the necessity of concepts like Kardeshev
Type I/II civilizations and Dyson spheres, which would aim to harness vast amounts of energy. Even
with much larger populations than today, the total energy use of human civilization would be orders of
magnitude below the threshold for causing direct thermal heating or reaching the scale of a Kardashev
Type I civilization. Any extraterrrestrial civilization that likewise achieves sustainable population
levels may also find a limit on its need to expand, which suggests that a galaxy-spanning civilization
as imagined in the Fermi paradox may not exist.
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.
The solar dynamo begins near the surfaceSérgio Sacani
The magnetic dynamo cycle of the Sun features a distinct pattern: a propagating
region of sunspot emergence appears around 30° latitude and vanishes near the
equator every 11 years (ref. 1). Moreover, longitudinal flows called torsional oscillations
closely shadow sunspot migration, undoubtedly sharing a common cause2. Contrary
to theories suggesting deep origins of these phenomena, helioseismology pinpoints
low-latitude torsional oscillations to the outer 5–10% of the Sun, the near-surface
shear layer3,4. Within this zone, inwardly increasing differential rotation coupled with
a poloidal magnetic field strongly implicates the magneto-rotational instability5,6,
prominent in accretion-disk theory and observed in laboratory experiments7.
Together, these two facts prompt the general question: whether the solar dynamo is
possibly a near-surface instability. Here we report strong affirmative evidence in stark
contrast to traditional models8 focusing on the deeper tachocline. Simple analytic
estimates show that the near-surface magneto-rotational instability better explains
the spatiotemporal scales of the torsional oscillations and inferred subsurface
magnetic field amplitudes9. State-of-the-art numerical simulations corroborate these
estimates and reproduce hemispherical magnetic current helicity laws10. The dynamo
resulting from a well-understood near-surface phenomenon improves prospects
for accurate predictions of full magnetic cycles and space weather, affecting the
electromagnetic infrastructure of Earth.
Extensive Pollution of Uranus and Neptune’s Atmospheres by Upsweep of Icy Mat...Sérgio Sacani
In the Nice model of solar system formation, Uranus and Neptune undergo an orbital upheaval,
sweeping through a planetesimal disk. The region of the disk from which material is accreted by
the ice giants during this phase of their evolution has not previously been identified. We perform
direct N-body orbital simulations of the four giant planets to determine the amount and origin of solid
accretion during this orbital upheaval. We find that the ice giants undergo an extreme bombardment
event, with collision rates as much as ∼3 per hour assuming km-sized planetesimals, increasing the
total planet mass by up to ∼0.35%. In all cases, the initially outermost ice giant experiences the
largest total enhancement. We determine that for some plausible planetesimal properties, the resulting
atmospheric enrichment could potentially produce sufficient latent heat to alter the planetary cooling
timescale according to existing models. Our findings suggest that substantial accretion during this
phase of planetary evolution may have been sufficient to impact the atmospheric composition and
thermal evolution of the ice giants, motivating future work on the fate of deposited solid material.
Exomoons & Exorings with the Habitable Worlds Observatory I: On the Detection...Sérgio Sacani
The highest priority recommendation of the Astro2020 Decadal Survey for space-based astronomy
was the construction of an observatory capable of characterizing habitable worlds. In this paper series
we explore the detectability of and interference from exomoons and exorings serendipitously observed
with the proposed Habitable Worlds Observatory (HWO) as it seeks to characterize exoplanets, starting
in this manuscript with Earth-Moon analog mutual events. Unlike transits, which only occur in systems
viewed near edge-on, shadow (i.e., solar eclipse) and lunar eclipse mutual events occur in almost every
star-planet-moon system. The cadence of these events can vary widely from ∼yearly to multiple events
per day, as was the case in our younger Earth-Moon system. Leveraging previous space-based (EPOXI)
lightcurves of a Moon transit and performance predictions from the LUVOIR-B concept, we derive
the detectability of Moon analogs with HWO. We determine that Earth-Moon analogs are detectable
with observation of ∼2-20 mutual events for systems within 10 pc, and larger moons should remain
detectable out to 20 pc. We explore the extent to which exomoon mutual events can mimic planet
features and weather. We find that HWO wavelength coverage in the near-IR, specifically in the 1.4 µm
water band where large moons can outshine their host planet, will aid in differentiating exomoon signals
from exoplanet variability. Finally, we predict that exomoons formed through collision processes akin
to our Moon are more likely to be detected in younger systems, where shorter orbital periods and
favorable geometry enhance the probability and frequency of mutual events.
Emergent ribozyme behaviors in oxychlorine brines indicate a unique niche for...Sérgio Sacani
Mars is a particularly attractive candidate among known astronomical objects
to potentially host life. Results from space exploration missions have provided
insights into Martian geochemistry that indicate oxychlorine species, particularly perchlorate, are ubiquitous features of the Martian geochemical landscape. Perchlorate presents potential obstacles for known forms of life due to
its toxicity. However, it can also provide potential benefits, such as producing
brines by deliquescence, like those thought to exist on present-day Mars. Here
we show perchlorate brines support folding and catalysis of functional RNAs,
while inactivating representative protein enzymes. Additionally, we show
perchlorate and other oxychlorine species enable ribozyme functions,
including homeostasis-like regulatory behavior and ribozyme-catalyzed
chlorination of organic molecules. We suggest nucleic acids are uniquely wellsuited to hypersaline Martian environments. Furthermore, Martian near- or
subsurface oxychlorine brines, and brines found in potential lifeforms, could
provide a unique niche for biomolecular evolution.
Continuum emission from within the plunging region of black hole discsSérgio Sacani
The thermal continuum emission observed from accreting black holes across X-ray bands has the potential to be leveraged as a
powerful probe of the mass and spin of the central black hole. The vast majority of existing ‘continuum fitting’ models neglect
emission sourced at and within the innermost stable circular orbit (ISCO) of the black hole. Numerical simulations, however,
find non-zero emission sourced from these regions. In this work, we extend existing techniques by including the emission
sourced from within the plunging region, utilizing new analytical models that reproduce the properties of numerical accretion
simulations. We show that in general the neglected intra-ISCO emission produces a hot-and-small quasi-blackbody component,
but can also produce a weak power-law tail for more extreme parameter regions. A similar hot-and-small blackbody component
has been added in by hand in an ad hoc manner to previous analyses of X-ray binary spectra. We show that the X-ray spectrum
of MAXI J1820+070 in a soft-state outburst is extremely well described by a full Kerr black hole disc, while conventional
models that neglect intra-ISCO emission are unable to reproduce the data. We believe this represents the first robust detection of
intra-ISCO emission in the literature, and allows additional constraints to be placed on the MAXI J1820 + 070 black hole spin
which must be low a• < 0.5 to allow a detectable intra-ISCO region. Emission from within the ISCO is the dominant emission
component in the MAXI J1820 + 070 spectrum between 6 and 10 keV, highlighting the necessity of including this region. Our
continuum fitting model is made publicly available.
HCL Notes und Domino Lizenzkostenreduzierung in der Welt von DLAUpanagenda
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We’ll show you how to fix common misconfigurations that cause higher-than-expected user counts, and how to identify accounts which you can deactivate to save money. There are also frequent patterns that can cause unnecessary cost, like using a person document instead of a mail-in for shared mailboxes. We’ll provide examples and solutions for those as well. And naturally we’ll explain the new licensing model.
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Characterizing interstellar filaments with herschel in ic5146
1. Astronomy & Astrophysics manuscript no. ic5146 c ESO 2011
March 2, 2011
Letter to the Editor
Characterizing interstellar filaments with Herschel in IC5146
D. Arzoumanian1 , Ph. Andr´ 1 , P. Didelon1 , V. K¨ nyves1 , N. Schneider1 , A. Men’shchikov1 , T. Sousbie2 , A. Zavagno3 ,
e o
S. Bontemps4 , J. Di Francesco5 , M. Griffin6 , M. Hennemann1 , T. Hill1 , J. Kirk6 , P. Martin7 , V. Minier1 , S. Molinari8 , F.
Motte1 , N. Peretto1 , S. Pezzuto8 , L. Spinoglio8 , D. Ward-Thompson6 , G. White9,11 , and C.D. Wilson10
(Affiliations can be found after the references)
Accepted: 17/02/2011
ABSTRACT
arXiv:1103.0201v1 [astro-ph.GA] 1 Mar 2011
We provide a first look at the results of the Herschel Gould Belt survey toward the IC5146 molecular cloud and present a preliminary analysis
of the filamentary structure in this region. The column density map, derived from our 70-500 µm Herschel data, reveals a complex network of
filaments, and confirms that these filaments are the main birth sites of prestellar cores. We analyze the column density profiles of 27 filaments and
show that the underlying radial density profiles fall off as r−1.5 to r−2.5 at large radii. Our main result is that the filaments seem to be characterized
by a narrow distribution of widths having a median value of 0.10 ± 0.03 pc, which is in stark contrast to a much broader distribution of central
Jeans lengths. This characteristic width of ∼ 0.1 pc corresponds to within a factor of ∼ 2 to the sonic scale below which interstellar turbulence
becomes subsonic in diffuse gas, supporting the argument that the filaments may form as a result of the dissipation of large-scale turbulence.
Key words. ISM: individual objects (IC5146) – Stars: formation – ISM: clouds – ISM: Filaments – ISM: structure – submillimeter
1. Introduction properties of the filaments seen in the Herschel images. Here,
we present new results from the Gould Belt survey obtained to-
Understanding how stars form out of the diffuse interstellar ward the IC5146 molecular cloud and analyze the radial den-
medium (ISM) on both global and local scales is a fundamen- sity profiles of the numerous filaments identified in this cloud.
tal open problem in contemporary astrophysics (see McKee & Based on a comparison with a similar analysis for the Aquila and
Ostriker 2007, for a recent review). Much observational progress Polaris regions, we show that the filaments of IC5146, Aquila,
is being made on this front thanks to the Herschel Space and Polaris are all characterized by a typical width of ∼ 0.1 pc
Observatory (Pilbratt et al. 2010). In particular, the first re- and discuss possible physical implications of this finding.
sults from the Gould Belt and Hi-GAL imaging surveys with
IC5146 is a star-forming cloud in Cygnus located at a dis-
Herschel have revealed a profusion of parsec-scale filaments in
tance of ∼ 460 pc (Lada et al. 1999, but see Appendix A), which
Galactic molecular clouds and suggested an intimate connection
consists of the Cocoon Nebula, an H ii region illuminated by the
between the filamentary structure of the ISM and the forma-
B0 V star BD + 46◦ 3474, and two parallel filamentary stream-
tion process of dense cloud cores (Andr´ et al. 2010; Molinari
e
ers extending to the west (Lada et al. 1994). In addition to these
et al. 2010). Remarkably, filaments are omnipresent even in un-
two streamers, the Herschel images reveal a whole network of
bound, non-star-forming complexes such as the Polaris translu-
filaments, which are the focus of the present letter.
cent cloud (Men’shchikov et al. 2010; Miville-Deschˆ nes et al.
e
2010; Ward-Thompson et al. 2010). Furthermore, in active star-
forming regions such as the Aquila Rift cloud, most of the
prestellar cores identified with Herschel are located within grav- 2. Observations and data reduction
itationally unstable filaments for which the mass per unit length
exceeds the critical value (Ostriker 1964), Mline,crit = 2 c2 /G ∼
s Our observations of IC5146 were made on 29 May 2010 in the
15 M /pc, where cs ∼ 0.2 km/s is the isothermal sound speed parallel scan-map mode of Herschel. An area of ∼1.6 deg2 was
for T ∼ 10 K. The early findings from Herschel led Andr´ e covered by both PACS (Poglitsch et al. 2010) at 70 µm, 160 µm
et al. (2010) to favour a scenario according to which core for- and SPIRE (Griffin et al. 2010) at 250 µm, 350 µm, 500 µm, with
mation occurs in two main steps. First, large-scale magneto- a scanning speed of 60 s−1 . The PACS data were reduced with
hydrodynamic (MHD) turbulence generates a whole network of HIPE version 3.0.1528. Standard steps of the default pipeline
filaments in the ISM (cf. Padoan et al. 2001; Balsara et al. 2001); were applied, starting from the raw data, taking special care
second, the densest filaments fragment into prestellar cores by of the deglitching and high-pass filtering steps. The final maps
gravitational instability (cf. Inutsuka & Miyama 1997). were created using the photProject task. The SPIRE observations
To refine this observationally-driven scenario of core forma- were reduced using HIPE version 3.0.1484. The pipeline scripts
tion and gain insight into the origin of the filamentary struc- were modified to include data taken during the turnaround of the
ture, an important step is to characterize the detailed physical telescope. A median baseline was applied and the ’naive’ map-
making method was used.
Herschel is an ESA space observatory with science instruments pro- Thanks to their unprecedented spatial dynamic range in the
vided by European-led Principal Investigator consortia and with impor- submillimeter regime, the Herschel images (see, e.g., online
tant participation from NASA. Fig. 5 and Fig. 6) provide a wealth of detailed quantitative in-
2. 2 D. Arzoumanian et al.: Characterizing interstellar filaments with Herschel in IC5146
Fig. 1. (a) Column density map derived from our SPIRE/PACS observations of IC5146. The resolution corresponds to the
36.9 HPBW resolution of SPIRE at 500 µm. The positions of the YSOs and starless cores detected with Herschel (using get-
sources, a source-finding algorithm described in Men’shchikov et al. 2010) are plotted as red stars and blue triangles respectively;
bound starless cores are in dark blue (cf. Fig. 6b and K¨ nyves et al. 2010, for classification details). The locations of the two fil-
o
aments (6 and 14) whose radial profiles are shown in Fig. 2 and online Fig. 4 are marked by the white rectangles. (b) Curvelet
component of the column density map, with the network of 27 identified filaments shown in blue.
formation on the large-scale, filamentary structure of the cloud. of a cylindrical filament with radial density and column density
It is this filamentary structure that we discuss in the following. profiles (as a function of cylindrical radius r) of the form:
ρc ρc Rflat
3. Analysis of the filamentary structure ρ p (r) = −→ Σ p (r) = A p p−1
, (1)
2 p/2
1 + (r/Rflat ) 1 + (r/Rflat )2 2
3.1. Identification of a network of filaments
Based on the Herschel images at five wavelengths, a dust temper- where Σ = µmH NH2 , µ = 2.33 is the mean molecular mass,
∞
ature (T d ) map (see online Fig. 6a) and a column density (NH2 ) A p = cos i −∞ (1+u2 ) p/2 is a finite constant factor for p > 1,
1 du
map (Fig. 1a) were constructed for IC5146, assuming the dust ρc is the density at the center of the filament, and Rflat is the
opacity law of Hildebrand (1983, see Appendix A) and follow- characteristic radius of the flat inner portion of the density pro-
ing the same procedure as K¨ nyves et al. (2010) for Aquila. We
o file1 . For simplicity, the inclination angle i of the model fil-
decomposed the column density map on curvelets and wavelets ament to the plane of the sky is assumed here to be i = 0
(e.g. Starck et al. 2003). The curvelet component image (Fig. 1b) (but see online Appendix A for the effect of i 0). At large
provides a high-contrast view of the filaments (after subtraction radii (r >> Rflat ), the model density profile approaches a power
of dense cores, which are contained in the wavelet component). law: ρ p (r) ∼ ρc (r/Rflat )−p . An important special case is the
We then applied the DisPerSE algorithm (Sousbie 2011) to the Ostriker (1964) model of an isothermal filament in hydrostatic
curvelet image to take a census of the filaments and trace their equilibrium, for which p = 4, A p = π/2, and Rflat corresponds
ridges. DisPerSE is a general method to identify structures such to the thermal Jeans length at the center of the filament, i.e.,
as filaments and voids in astrophysical data sets (e.g. gridded Rflat ≡ λJ (r = 0) = c2 / (GΣr=0 ).
s
maps). The method, based on principles of computational topol- When fitting such a model profile to the observations, ρc ,
ogy, traces filaments by connecting saddle points to maxima Rflat , and p, along with the peak position of the filament, were
with integral lines. From the filaments identified with DisPerSE treated as free parameters. The results (see, e.g., Fig. 2 and on-
above a ’persistence’ threshold of 5 × 1020 cm−2 in column den- line Table 1) show that the observed profiles are generally well
sity (∼ 5σ in the curvelet map), we built a mask on the same grid fitted with 1.5 < p < 2.5. None of the observed filaments has
as the input map, with values of 1 along the filament ridges and the steep p = 4 density profile of the Ostriker (1964) model. A
0 elsewhere (cf. Sousbie 2011, for a definition of ’persistence’). similar conclusion was already reported by Lada et al. (1999) in
Based on the skeleton mask obtained for IC5146, we identified the case of the main streamer (i.e., Filament 6 here).
and numbered a total of 27 filaments (shown in blue in Fig. 1b). The above radial profile analysis can also be used to de-
rive accurate masses per unit length, Mline , for the filaments
3.2. Radial density profiles of the filaments by integrating column density over radius: Mline = Σobs (r)dr.
The main source of uncertainty lies in the difficulty of defining
To construct the mean radial density profile of each filament, the the edges of the filaments, especially in crowded regions. The
tangential direction to the filament’s ridge was first computed at method is nevertheless quite robust when the bounds of inte-
each pixel position along the filament. Using the original column gration are reasonably well defined (cf. Fig. 2). The values of
density map (cf. Fig. 1a), we then measured a radial column den-
sity profile perpendicular to the ridge at each position. Finally, 1
Model profiles of the form described by Eq. (1) are sometimes
we derived the mean radial profile by averaging all of the profiles called Plummer-like (cf. Nutter et al. 2008, and references therein).
along the filament (see Fig. 2). In order to characterize each ob- When Rflat is much smaller than the spatial resolution of the observa-
served (column) density profile, we adopted an idealized model tions, such profiles are effectively equivalent to power laws.
3. D. Arzoumanian et al.: Characterizing interstellar filaments with Herschel in IC5146 3
Fig. 2. (a) Mean radial column density profile perpendicular to the supercritical filament labeled 6 in Fig. 1b (black curve). The area
in yellow shows the dispersion of the radial profile along the filament. The inner curve in light blue corresponds to the effective
36.9 HPBW resolution (0.08 pc at 460 pc) of the column density map of Fig. 1a used to construct the profile. The dotted red
curve shows the best-fit model of the form expressed by Eq. (1), with p = 2. For comparison, the dashed blue curve shows a model
with p = 4, corresponding to a hydrostatic isothermal equilibrium filament (Ostriker 1964). The two dashed vertical segments at
∼ ±1.5 pc mark the bounds within which the profile was integrated to estimate the mass per unit length Mline . (b) Mean radial dust
temperature profile measured perpendicular to filament 6. (c) Same as (a) displayed in log-log format to better visualize the flatter
inner part of the profile and the power-law behavior at large radii.
Mline derived with this method (see online Table 1) are typi- Aquila and Polaris fields, also observed by us with Herschel.
cally 20% higher than simpler estimates assuming that the fila- The Aquila region is a very active star-forming complex at
ments have Gaussian column density profiles (cf. Appendix of d ∼ 260 pc (e.g. Bontemps et al. 2010, and references therein),
Andr´ et al. 2010). Most bound prestellar cores appear to be
e while the Polaris field is a high-latitude translucent cloud with
located within supercritical, gravitationally unstable filaments little to no star formation at d ∼ 150 pc (e.g. Ward-Thompson
with Mline > Mline,crit (e.g. Filament 6 – see online Fig. 6b), a et al. 2010, and references therein). Following the same proce-
similar result to that already obtained by Andr´ et al. (2010) in
e dure as in Sect. 3.1, we identified 32 filaments in Aquila and
Aquila. Note that both methods of estimating Mline (profile in- 31 filaments in Polaris spanning three orders of magnitude in
tegration or Gaussian approximation) yield essentially the same central column density from ∼ 1020 cm−2 for the most tenuous
conclusion on the gravitational instability of the filaments. filaments of Polaris to ∼ 1023 cm−2 for the densest filaments of
Aquila (see also Fig. 1 of Andr´ et al. 2010). The distribution
e
of deconvolved FWHM widths for the combined sample of 90
4. A characteristic width for interstellar filaments ? filaments is shown in online Fig. 7b. This combined distribution
To construct a reliable distribution of filament widths (cf. online is sharply peaked at 0.10 ± 0.03 pc, which strengthens the trend
Fig. 7a), we applied Gaussian fits to the radial column density noted above for IC5146. While further tests would be required
profiles, as these tend to be more robust than the more sophisti- to fully investigate potential biases (especially given uncertain-
cated fits discussed in Sect. 3.2. A Gaussian fit to a model pro- ties in cloud distances – see Appendix A) and reach a definitive
file of the form of Eq. (1) with p = 2 indicates that the derived conclusion, our present findings suggest that most interstellar fil-
FWHM width is equivalent to ∼ 1.5 × (2 Rflat ). It can be seen aments may share a similar characteristic width of ∼ 0.1 pc.
in Fig. 7a that the filaments of IC5146 have a narrow distribu-
tion of deconvolved FWHM widths centered around a typical 5. Discussion
(median) value of 0.10 ± 0.03 pc (see also Fig. 3). Note that the
same filaments span more than an order of magnitude in central The results presented in Sect. 3 and Sect. 4 can be used to discuss
column density (cf. online Table 1), implying a distribution of the formation and evolution of the observed filamentary struc-
central Jeans lengths [λJ (r = 0) = c2 / (GΣr=0 )] from ∼ 0.02 pc
s ture. Three broad classes of models have been proposed in the
to > 0.3 pc, which is much broader than the observed distribu- literature to account for filaments in molecular clouds, depend-
tion of widths (see Fig. 3 and blue dashed line in Fig. 7a). ing on whether global gravity (e.g. Heitsch et al. 2008), magnetic
In order to check that the measured filament widths were not fields (e.g. Nakamura & Li 2008), or large-scale turbulence (e.g.
strongly affected by the finite resolution of the column density Padoan et al. 2001; Mac Low & Klessen 2004) play the domi-
map, we performed the same radial profile analysis using the nant role. Large-scale gravity can hardly be invoked to form fila-
SPIRE 250 µm map, which has a factor ∼ 2 better resolution ments in gravitationally unbound complexes such as the Polaris
(18.1 HPBW). The resulting distribution of filament widths is flare cloud (cf. Heithausen & Thaddeus 1990). While magnetic
shown as a dotted histogram in online Fig. 7a and is statistically fields may play an important role in channeling mass accumu-
very similar to the original distribution at 36.9 resolution (at the lation onto the densest filaments (e.g. Goldsmith et al. 2008,
50% confidence level according to a Kolmogorov-Smirnov test). Nakamura & Li 2008), our Herschel findings appear to be con-
We also performed a similar analysis of the filamentary sistent with the turbulent picture. In the scenario proposed by
structure in two other regions located at different distances, the Padoan et al. (2001), the filaments correspond to dense, post-
4. 4 D. Arzoumanian et al.: Characterizing interstellar filaments with Herschel in IC5146
shock stagnation gas associated with regions of converging su-
personic flows. One merit of this scenario is that it provides an
explanation for the typical ∼ 0.1 pc width of the filaments as
measured with Herschel (Sect. 4 and Fig. 3). In a plane-parallel
shock, the thickness λ of the postshock gas layer/filament is re-
lated to the thickness L of the preshock gas by λ ≈ L/M(L)2 ,
where M(L) is the Mach number and M(L)2 is the compression
ratio of the shock for a roughly isothermal radiative hydrody-
namic shock. Thus, the thickness λ is independent of the scale L
given Larson’s linewidth–size relation [M(L) ∝ σv (L) ∝ L0.5 ].
In this picture, the postshock thickness of the filaments effec-
tively corresponds to the sonic scale λs at which the 3D turbu-
lent velocity dispersion equals the sound speed (i.e., M(λs ) = 1),
leading to λ ≈ λs ∼ 0.05–0.15 pc according to recent determina-
tions of the linewidth–size relationship in molecular clouds (e.g.
Heyer et al. 2009; Federrath et al. 2010).
If large-scale turbulence provides a plausible mechanism for
forming the filaments, the fact that prestellar cores tend to form Fig. 3. Mean deconvolved width (FWHM) versus mean central
in gravitationally unstable filaments (Andr´ et al. 2010) suggests
e column density for the 27 filaments of IC5146 shown in Fig 1b,
that gravity is a major driver in the subsequent evolution of the along with 32 filaments in Aquila and 31 filaments in Polaris, all
filaments. The power-law shape of the outer density profiles, analyzed in the same way (see Sect. 3). The spatial resolutions
especially in the case of supercritical filaments (Sect. 3.2 and of the column density maps used in the analysis for the three
Fig. 2), is also suggestive of the role of gravity. Although the ob- regions are marked by the horizontal dotted lines. The filament
served profiles are shallower than the profile of a self-gravitating width has a typical value of ∼ 0.1 pc, regardless of central col-
isothermal equilibrium filament (Ostriker 1964), they are consis- umn density. The solid line running from top left to bottom right
tent with some models of magnetized filaments in gravitational shows the central (thermal) Jeans length as a function of central
virial equilibrium (Fiege & Pudritz 2000). Another attractive ex- column density [λ J = c2 / (GΣ0 )] for a gas temperature of 10 K.
s
planation of the observed ρ ∼ r−2 profiles is that the filaments
are not strictly isothermal and that some of them are collapsing.
Nakamura & Umemura (1999) have shown that the cylindrical Herschel filaments in several regions would be extremely valu-
version of the Larson-Penston similarity solution for the col- able to confirm the validity of the scenario proposed here.
lapse of a filament has an outer density profile which approaches
ρ ∝ r−2 when the equation of state is not isothermal but poly- Acknowledgements. SPIRE has been developed by a consortium of institutes led
tropic (P ∝ ργ ) with γ < 1. The dust temperature profiles derived
∼
by Cardiff Univ. (UK) and including Univ. Lethbridge (Canada); NAOC (China);
CEA, LAM (France); IFSI, Univ. Padua (Italy); IAC (Spain); Stockholm
for the IC5146 filaments generally show a slight, but significant Observatory (Sweden); Imperial College London, RAL, UCL-MSSL, UKATC,
temperature drop toward the center of the filaments (cf. Fig. 2b), Univ. Sussex (UK); Caltech, JPL, NHSC, Univ. Colorado (USA). This develop-
suggesting that a polytropic equation of state with γ < 1 may in-
∼ ment has been supported by national funding agencies: CSA (Canada); NAOC
deed be more appropriate than a simple isothermal assumption. (China); CEA, CNES, CNRS (France); ASI (Italy); MCINN (Spain); SNSB
(Sweden); STFC (UK); and NASA (USA). PACS has been developed by a
The lack of anti-correlation between filament width and cen- consortium of institutes led by MPE (Germany) and including UVIE (Austria);
tral column density (see Fig. 3) provides another strong con- KUL, CSL, IMEC (Belgium); CEA, OAMP (France); MPIA (Germany); IFSI,
straint on filament evolution. If the filaments are initially formed OAP/AOT, OAA/CAISMI, LENS, SISSA (Italy); IAC (Spain). This develop-
with a characteristic thickness ∼ 0.1 pc as a result of turbulent ment has been supported by the funding agencies BMVIT (Austria), ESA-
PRODEX (Belgium), CEA/CNES (France), DLR (Germany), ASI (Italy), and
compression (see above), then the left-hand (subcritical) side of CICT/MCT (Spain).
Fig. 3 can be readily understood. The right-hand (supercritical)
side of Fig. 3 is more surprising since one would naively ex-
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1Laboratoire AIM, CEA/DSM–CNRS–Universit´ e Paris
Diderot, IRFU/Service d’Astrophysique, C.E.A. Saclay,
Orme des Merisiers, 91191 Gif-sur-Yvette, France e-mail:
doris.arzoumanian@cea.fr, pandre@cea.fr
2
Institute d’Astrophysique de Paris, UMR 7095 CNRS, Universit´ e
Pierre et Marie Curie, 98 bis Boulevard Arago, F-75014 Paris, France
3
Laboratoire d’Astrophysique de Marseille, CNRS/INSU–
Universit´ de Provence, 13388 Marseille cedex 13, France
e
4
Universit´ de Bordeaux, OASU, Bordeaux, France
e
5
National Research Council of Canada, Herzberg Institute of
Astrophysics, University of Victoria, Department of Physics and
Astronomy, Victoria, Canada
6
School of Physics & Astronomy, Cardiff University, Cardiff, UK
7
Canadian Institute for Theoretical Astrophysics, University of
Toronto, Toronto, ON M5S 3H8, Canada
8
IFSI - INAF, via Fosso del Cavaliere 100, I-00133 Roma, Italy
9
The Rutherford Appleton Laboratory, Chilton, Didcot OX11 0NL,
UK
10
Department of Physics and Astronomy, McMaster University,
Hamilton, ON L8S 4M1, Canada
11
Department of Physics & Astronomy, The Open University,
Milton Keynes, UK
6. D. Arzoumanian et al.: Characterizing interstellar filaments with Herschel in IC5146, Online Material p 1
Appendix A: Effects of distance and dust opacity
uncertainties and influence of the viewing angle
There is some ambiguity concerning the distance to IC5146. The
default distance adopted in this paper corresponds to the value
of 460+40 pc derived from star counts by Lada et al. (1999).
−60
However, other studies placed the IC5146 cloud at a distance of
950 ± 80 pc based on photometry and spectra of late-B stars in
the IC5146 cluster (e.g. Harvey et al. 2008). If the true distance
of IC5146 were ∼ 950 pc instead of ∼ 460 pc, then the widths of
the IC5146 filaments would all be a factor of ∼ 2 larger than the
values listed in Col. 6 of Table 1, leading to a median width of z
0.2 ± 0.06 pc instead of 0.1 ± 0.03 pc. This would also broaden
the distribution of FWHM widths for the combined sample of 90
filaments in IC5146, Aquila, and Polaris (see dotted histogram
in online Fig. 7b). As can be seen in online Fig. 7b, our main re-
sult that the typical filament width is ∼ 0.1 pc to within a factor
of ∼ 2 would nevertheless remain valid. We also stress that the Fig. 4. Mean radial column density profile in log-log format of
distance uncertainty has no effect on the shape of the radial col- the subcritical filament labeled 14 in Fig. 1b (western side). Note
umn density profiles (Sect. 3.2 and Fig. 2) or on the absence of that, given the relatively large dispersion of the radial profile
an anti-correlation between filament width and central column along the filament (shown in yellow), the power-law behavior
density in Fig. 3. at large radii is less clear in this subcritical case than for the su-
The following (temperature-independent) dust opacity law percritical filament shown in Fig. 2c.
was assumed in our analysis of the Herschel data:
κν = 0.1 × (ν/1000 GHz)2 cm2 /g, where ν denotes frequency and
κν is the dust opacity per unit (gas + dust) mass column den- the observed masses per unit length (Col. 12 of Table 1) tend to
sity. This dust opacity law is very similar to that advocated by overestimate the true masses per unit length of the filaments by
Hildebrand (1983) at submillimeter wavelengths, and is consis- ∼ 60% on average. Although systematic, this inclination effect
tent with the mean value κ850µ ≈ 0.01 cm2 /g derived by Kramer remains less than a factor of 2 and thus has little impact on the
et al. (2003) in IC5146 from a detailed comparison of their classification of observed filaments in thermally subcritical and
SCUBA 850 µm and 450 µm data with the near-infrared extinc- thermally supercritical filaments.
tion map of Lada et al. (1999). However, Kramer et al. (2003)
found evidence of an increase in the dust opacity κ850µ by a fac-
tor of ∼ 4 when the dust temperature T d decreased from ∼ 20 K
to ∼ 12 K, which they interpreted as the manifestation of dust
grain evolution (e.g. coagulation and formation of ice mantles)
in the cold, dense interior of the cloud. The dust temperature
map derived from Herschel data (see Fig. 6a) suggests that T d
ranges from ∼ 11 K to ∼ 17 K in the bulk of IC5146, with the
exception of the PDR region associated with the Cocoon Nebula
where T d reaches ∼ 30 K. Assuming a linear increase in κν by
a factor of 4 when T d decreases from ∼ 20 K to ∼ 12 K as sug-
gested by the Kramer et al. (2003) study, we estimate that the
column density map shown in Fig. 1a is accurate to better than
a factor of ∼ 2 over most of its extent. The possible dependence
of κν on temperature has very little impact on our analysis of
the filament profiles. For filament 6, for instance, T d decreases
by less than ∼ 3 K from the exterior to the interior of the fila-
ment (see Fig. 2b), suggesting that κν does not change by more
than ∼ 40% from large to small radii. The potential effect on the
estimated FWHM width, W, and power-law index, p, of the fil-
ament profiles is even smaller: W would increase, and p would
decrease, by less than ∼ 3% and ∼ 7%, respectively.
Our Herschel observations only provide information on the
projected column density profile Σobs (r) = cos i Σint (r) of any
1
given filament, where i is the inclination angle to the plane of
the sky and Σint is the intrinsic column density profile of the
filament. For a population of randomly oriented filaments with
respect to the plane of the sky, the net effect is that Σobs overes-
timates Σint by a factor < cos i > = π ∼ 1.57 on average. This
1
2
does not affect our analysis of the shape of the radial column
density profiles (Sect. 3.2), but implies that the central column
densities of the filaments are actually ∼ 60% lower on average
than the projected values listed in Col. 2 of Table 1. Likewise,
7. D. Arzoumanian et al.: Characterizing interstellar filaments with Herschel in IC5146, Online Material p 2
Fig. 5. (a) Composite 3-color image of IC5146 (∼ 1.6 deg2 field) produced from our PACS/SPIRE parallel-mode data at 70, 250,
and 500µm. The color coding is such that red = SPIRE 500 µm, green = SPIRE 250 µm, blue = PACS 70 µm. (b) SPIRE 250 µm
image of IC5146.
Fig. 6. (a) Dust temperature map derived from our SPIRE/PACS observations of IC5146. The resolution corresponds to the
36.9 HPBW resolution of SPIRE at 500 µm. (b) Curvelet component of the column density map of IC5146 (cf. Fig. 1), in
which the areas where the filaments have a mass per unit length larger than half the critical value and are thus likely gravitationally
unstable have been highlighted in white. The positions of the 71 YSOs and 45 candidate bound prestellar cores identified with
getsources (Men’shchikov et al. 2010) in the Herschel images are overplotted as red stars and dark blue triangles, respectively.
Candidate bound prestellar cores were selected among a larger population of starless cores (see blue triangles in Fig. 1a), on the
basis of a comparison of the core masses with local values of the Jeans or Bonnor-Ebert mass (see Sect. 4.1 of K¨ nyves et al. 2010,
o
for details). Note the excellent correspondence between the spatial distribution of the prestellar cores and the supercritical filaments,
in agreement with our earlier results in Aquila and Polaris (see Fig. 2 of Andr´ et al. 2010).
e
8. D. Arzoumanian et al.: Characterizing interstellar filaments with Herschel in IC5146, Online Material p 3
Table 1. Summary of derived parameters for the 27 filaments of IC5146
Filament 0
NH2 σNH2 (a) 0
Td σTd (a) FWHMdec σ FWHMdec (a) λ0
J σλJ (a)
p (b) Rflat (b) Mline (c)
[10 cm−2 ]
21
[K] [pc] [pc] [pc] [M /pc]
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12)
1 1.8 0.2 15.4 0.6 0.12 0.02 0.11 0.09 2.1 0.05 9
2 4.8 4.4 13.9 0.7 0.11 0.03 0.07 0.09 1.9 0.06 21
3 1.6 0.3 12.6 0.5 0.11 0.02 0.07 0.05 – – 2
4 1.6 0.5 13.5 0.5 0.10 0.06 0.09 0.07 1.4 0.02 8
5 7.5 4.5 12.1 0.6 0.06 0.05 0.04 0.04 1.5 0.01 28
6 16 7.6 11.8 0.9 0.12 0.04 0.02 0.01 1.7 0.04 152
7 5.6 2.4 12.1 0.5 0.09 0.04 0.03 0.02 1.6 0.03 22
8 2.0 0.7 13.6 0.5 0.08 0.03 0.15 0.01 1.5 0.05 6
9 3.3 1.3 12.5 0.3 0.14 0.02 0.05 0.06 1.5 0.04 10
10 3.3 0.6 13.6 0.4 0.14 0.03 0.10 0.02 2.1 0.06 14
11 5.3 2.5 11.7 0.5 0.08 0.03 0.05 0.03 1.9 0.04 15
12 12 4.1 11.7 1.0 0.18 0.03 0.02 0.01 1.5 0.03 41
13 6.9 5.8 12.7 0.8 0.08 0.03 0.04 0.09 1.6 0.02 23
14 (d) 1.5 0.8 13.7 0.5 0.13 0.03 0.21 0.01 1.5–2.4 0.04–0.14 13
15 2.1 2.2 14.7 1.1 0.11 0.04 0.16 0.06 – – 4
16 (e) 3.3 0.9 26.9 2.1 0.12 0.02 0.19 0.05 – – 12
17 (e) 2.0 1.7 18.3 2.9 0.09 0.05 0.20 0.29 1.3 0.04 6
18 (e) 3.9 2.0 22.2 2.6 0.11 0.04 0.12 0.09 – – 49
19 (e) 3.6 1.5 26.5 1.2 0.09 0.03 0.17 0.08 1.9 0.08 1
20 0.57 0.5 15.5 0.5 0.08 0.02 0.24 0.01 1.5 0.03 3
21 1.5 0.5 14.0 0.4 0.13 0.03 0.09 0.06 1.7 0.05 6
22 (f) 0.8 0.1 13.5 0.3 < 0.06 0.19 0.32 0.05 – – 1
23 (d) 1.4 0.4 13.2 0.7 0.14 0.07 0.09 0.07 1.5–1.8 0.04–0.06 7
24 5.6 1.1 12.3 0.2 0.07 0.03 0.05 0.01 – – 21
25 2.2 1.5 12.7 0.5 0.10 0.03 0.09 0.01 1.5 0.03 11
26 (d) 1.5 0.3 12.5 0.4 0.10 0.06 0.19 0.04 1.5–2.1 0.05– 0.08 2
27 (f) 2.9 1.0 11.5 0.3 < 0.06 0.03 0.03 0.03 1.4 0.02 13
mean 3 1 13.5 0.5 0.10 0.03 0.09 0.05 1.6 0.03 11
range 0.6-16 0.1–7.6 11–27 0.2–2.9 0.06–0.18 0.02–0.19 0.02–0.32 0.01–0.29 1.3–2.4 0.01–0.08 1–152
rms 3.4 1.9 4.1 0.7 0.03 0.03 0.07 0.06 0.3 0.02 30
Notes: Col. 2, Col. 4, Col. 8: Mean projected column density, dust temperature, and Jeans length estimated at the center of each filament.
Col. 6: Weighted mean of the distribution of deconvolved FWHM widths resulting from Gaussian fits to the radial profiles at each position
along the filament. (a) The quoted dispersion is the standard deviation of the distribution of the measured parameter along each filament. In the
case of FWHMdec (Col. 6), this dispersion (Col. 7) is larger than the error bar plotted in Fig. 3 which corresponds to the standard deviation
of the mean deconvolved FWHM width. (b) p and Rflat correspond to the best-fit model of the form expressed by Eq. (1) to the mean column
density profile of each filament. The fit was weighted by 1/σ(r)2 where σ(r) is the standard deviation of the radial profile at projected radius
r, estimated from the measured (1σ) dispersion along the filament. The same bounds (shown as vertical dashed lines in Figs. 2a, 2c, 4 for
filaments 6 and 14) were used to fit the profiles and to calculate the mass per unit length by integrating over the radial profile. (c) Col. 12
gives to the projected mass per unit length obtained by integrating over the observed column density profile of each filament. The thermally
supercritical filaments with Mline > Mline,crit are indicated in boldface, where Mline,crit = 2 c2 /G ∼ 20 M /pc (for a gas temperature T ∼ 12 K,
s
corresponding to the median central dust temperature measured here, ignoring the temperatures of the filaments located in the PDR region).
(d)
Filaments 14, 23, and 26 have asymmetric radial profiles. A separate fit was thus performed on either side of each of these three filaments.
The values of p and Rflat reported in Col. 10 and Col. 11 correspond to the best-fit values on either side of these filaments. (e) Filaments 16, 17,
18, and 19 are located in the PDR region called the Cocoon Nebula (see Fig. 1a and online Fig. 5), and their derived dust temperatures may be
overestimated. (f) Filaments 22 and 27 have unresolved widths and are shown as upper limits corresponding to 75% of the HPBW resolution
in Fig. 3.
9. D. Arzoumanian et al.: Characterizing interstellar filaments with Herschel in IC5146, Online Material p 4
Table 2. Median values of observed angular widths and deconvolved physical widths(a) for three samples of filaments and two
angular resolutions
Field distance [pc] From column density maps with 36.9 resolution From SPIRE 250 µm images with 18.1 resolution
FWHMobs σFWHMobs FWHMdec σFWHMdec FWHMobs σFWHMobs FWHMdec σFWHMdec
[ ] [ ] [pc] [pc] [ ] [ ] [pc] [pc]
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
IC5146 460 59 15 0.10 0.03 44 10 0.09 0.02
Aquila 260 94 21 0.11 0.03 97 31 0.12 0.04
Polaris 150 94 24 0.06 0.02 74 20 0.05 0.02
All(b) 0.10 0.03 0.09 0.02
Notes: Col. 3 and Col. 7: Median value of the observed FWHM angular width before deconvolution. Col. 5 and Col. 9: Median value of the
deconvolved FWHM physical width. Col. 4, Col. 6, Col. 8, Col. 10: Dispersion (standard deviation) of the distribution of widths for each
filament sample. (a) The DisPerSE algorithm (Sousbie 2011) we used to trace filaments in the column density maps derived from Herschel
data does not consider filamentary width in its process of identifying filaments. While it is difficult to assess the completeness of our census of
filamentary structures without dedicated tests (which will be the subject of future work), there is in principle no bias toward selecting structures
of similar width with DisPerSE. (b) The last row refers to the combined sample of 90 filaments observed in IC5146, Aquila, and Polaris.
Fig. 7. (a) Distribution of deconvolved FWHM widths for the 27 filaments of IC5146 (black solid histogram, filled in orange). These
widths have been deconvolved from the 36.9 HPBW resolution of the column density map (Fig. 1a) used to construct the radial
profiles of the filaments. The median width is 0.10 pc and the standard deviation of the distribution is 0.03 pc. The black dotted
histogram shows the distribution of deconvolved FWHM widths measured on the SPIRE 250 µm map which has a factor ∼ 2 better
resolution (18.1 HPBW). . This distribution is statistically indistinguishable from the distribution obtained at 36.9 resolution. The
two down pointing arrows in the upper left mark the resolution limits for the distributions at 36.9 and 18.1 , i.e., 0.08 pc and
0.04 pc, respectively. For comparison, the blue dashed histogram represents the distribution of central Jeans lengths corresponding
to the central column densities of the filaments. (b) Distributions of deconvolved FWHM widths for a larger sample of 90 filaments,
combining the 27 filaments of IC5146, 32 filaments in Aquila, and 31 filaments in Polaris, all analyzed in the same way from column
density maps with 36.9 resolution as explained in Sect. 3 and Sect. 4. The black solid histogram, filled in orange, is based on our
default distance assumptions: 460 pc for IC5146, 260 pc for Aquila, and 150 pc for Polaris. This distribution has a median of 0.10 pc
and a standard deviation of 0.03 pc. The horizontal double arrow at the upper left shows the range of HPBW resolution limits, going
from ∼ 0.03 pc for Polaris to ∼ 0.08 pc for IC5146. The dotted histogram shows an alternate distribution of deconvolded widths
for the same sample of filaments based on other distance assumptions: 950 pc for IC5146 (see Appendix A), 400 pc for Aquila (see
discussion in Bontemps et al. 2010, and Appendix of Andr´ et al. 2010), and 150 pc for Polaris. The median value of this alternate
e
distribution is 0.15 pc and the standard deviation is 0.08 pc. For comparison, the blue dashed histogram represents the distribution
of central Jeans lengths corresponding to the central column densities of the 90 filaments (independent of distance).