- ID:
- ivo://CDS.VizieR/J/A+A/645/A55
- Title:
- Catalogue of cold cores in Perseus
- Short Name:
- J/A+A/645/A55
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The complex of star-forming regions in Perseus is one of the most studied due to its proximity (about 300pc). In addition, its regions show variation in star-formation activity and age, with formation of low-mass and intermediate-mass stars. In this paper, we present analyses of images taken with the Herschel ESA satellite from 70 um to 500 um. From these images, we first constructed column density and dust temperature maps. We then identified compact cores in the maps at each wavelength, and characterised the cores using modified blackbody fits to their spectral energy distributions (SEDs): we identified 684 starless cores, of which 199 are bound and potential prestellar cores, and 132 protostars. We also matched the Herschel-identified young stars with GAIA sources to model distance variations across the Perseus cloud. We measure a linear gradient function with right ascension and declination for the entire cloud. This function is the first quantitative attempt to derive the gradient in distance across Perseus, from east to west, in an analytical form. We derived mass and temperature of cores from the SED fits. The core mass function can be modelled with a log-normal distribution that peaks at 0.82M_{sun}_ suggesting a star formation efficiency of 0.30 for a peak in the system initial mass function of stars at 0.25M_{sun}_. The high-mass tail can be modelled with a power law of slope ~-2.32, which is close to the Salpeter's value. We also identify the filamentary structure of Perseus and discuss the relation between filaments and star formation, confirming that stars form preferentially in filaments. We find that the majority of filaments with ongoing star formation are transcritical against their own internal gravity because their linear masses are below the critical limit of 16M_{sun}_/pc above which we expect filaments to collapse. We find a possible explanation for this result, showing that a filament with a linear mass as low as 8 Msun/pc can already be unstable. We confirm a linear relationship between star formation efficiency and the slope of dust probability density function, and we find a similar relationship with the core formation efficiency. We derive a lifetime for the prestellar core phase of 1.69+/-0.52Myr for the whole Perseus complex but different regions have a wide range in prestellar core fractions, suggesting that star formation began only recently in some clumps. We also derive a free-fall time for prestellar cores of 0.16Myr.
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- ID:
- ivo://CDS.VizieR/J/A+A/569/A7
- Title:
- CB17 dust emission (100-500um), N(H) and T maps
- Short Name:
- J/A+A/569/A7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The initial conditions for the gravitational collapse of molecular cloud cores and the subsequent birth of stars are still not well constrained. The characteristic cold temperatures (~10K) in such regions require observations at sub-millimetre and longer wavelengths. The Herschel Space Observatory and complementary ground-based observations presented in this paper have the unprecedented potential to reveal the structure and kinematics of a prototypical core region at the onset of stellar birth. This paper aims to determine the density, temperature, and velocity structure of the star-forming Bok globule CB 17. This isolated region is known to host (at least) two sources at different evolutionary stages: a dense core, SMM1, and a Class I protostar, IRS. We modeled the cold dust emission maps from 100{mu}m to 1.2mm with both a modified blackbody technique to determine the optical depth-weighted line-of-sight temperature and column density and a ray-tracing technique to determine the core temperature and volume density structure. Furthermore, we analysed the kinematics of CB17 using the high-density gas tracer N_2_H^+
- ID:
- ivo://CDS.VizieR/J/A+A/649/A31
- Title:
- [CCJ2015b] HZ4 [CII] 158um datacube
- Short Name:
- J/A+A/649/A31
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- We present new Atacama Large Millimeter/Submillimeter Array (ALMA) observations of the [CII] 158um transition and the dust continuum in HZ4, a typical star-forming galaxy when the Universe was only ~1Gyr old (z~5.5). Our high ~0.3" spatial resolution allows us to study the relationships between [CII] line emission, star formation rate, and far-infrared emission on spatial scales of ~2kpc. In the central ~4kpc of HZ4 the [CII]/FIR is ~3x10^-3^ on global scales as well as on spatially resolved scales of ~2kpc, comparable to the ratio observed in local moderate starburst galaxies such as M82 or M83. For the first time in an individual normal galaxy at this redshift, we find evidence for outflowing gas from the central star-forming region in the direction of the minor axis of the galaxy. The projected velocity of the outflow is ~400km/s, and the neutral gas-mass outflow rate is ~3-6 times higher than the star formation rate in the central region. Finally, we detect a diffuse component of [CII] emission, or [CII] halo, that extends beyond the star-forming disk and has a diameter of ~12kpc. The outflow, which has a velocity approximately half of the escape velocity of the system, most likely partly fuels the [CII] extended emission. Together with the kinematic analysis of HZ4 (presented in a forthcoming paper), the analysis supports the hypothesis that HZ4 is a typical star-forming disk at z~5 with interstellar medium conditions similar to present-day galaxies forming stars at a similar level, driving a galactic outflow that may already play a role in its evolution.
- ID:
- ivo://CDS.VizieR/J/A+A/573/A19
- Title:
- Cep OB2 Herschel/PACS view
- Short Name:
- J/A+A/573/A19
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The CepOB2 region, with its two intermediate-aged clusters Tr37 and NGC7160, is a paradigm of sequential star formation and an ideal site for studies of protoplanetary disk evolution. We use Herschel data to study the protoplanetary disks and the star formation history of the region. Herschel/PACS observations at 70 and 160{mu}m probe the disk properties (mass, dust sizes, structure) and the evolutionary state of a large number of young stars. Far-IR data also trace the remnant cloud material and small-scale cloud structure. We detect 95 protoplanetary disks at 70{mu}m, 41 at 160{mu}m, and obtain upper limits for more than 130 objects. The detection fraction at 70{mu}m depends on the spectral type (88% for K4 or earlier stars, 17% for M3 or later stars) and on the disk type (~50% for full and pre-transitional disks, ~35% for transitional disks, no low-excess/depleted disks detected). Non-accreting disks are not detected, suggesting significantly lower masses. Accreting transition and pre-transition disks have systematically higher 70{mu}m excesses than full disks, suggestive of more massive, flared and/or thicker disks. Herschel data also reveal several mini-clusters in Tr37, which are small, compact structures containing a few young stars surrounded by nebulosity. Far-IR data are an excellent probe of the evolution of disks that are too faint for sub-millimetre observations. We find a strong link between far-IR emission and accretion, and between the inner and outer disk structure. Herschel confirms the dichotomy between accreting and non-accreting transition disks. Accretion is a powerful measure of global disk evolution: substantial mass depletion and global evolution need to occur to shut down accretion in a protoplanetary disk, even if the disk has inner holes. Disks likely follow different evolutionary paths: low disk masses do not imply opening inner holes, and having inner holes does not require low disk masses. The mini-clusters reveal multi-episodic star formation in Tr37. The long survival of mini-clusters suggest that they formed from the fragmentation of the same core. Their various morphologies favour different formation/triggering mechanisms acting within the same cluster. The beads-on-a-string structure in one mini-cluster is consistent with gravitational fragmentation or gravitational focusing, acting on very small scales (solar-mass stars in ~0.5pc filaments). Multi-episodic star formation could also produce evolutionary variations between disks in the same region. Finally, Herschel also unveils what could be the first heavy mass loss episode of the O6.5 star HD 206267 in Tr 37.
- ID:
- ivo://CDS.VizieR/J/A+A/527/A145
- Title:
- Chamaeleon I 870um sources
- Short Name:
- J/A+A/527/A145
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Chamaeleon I is the most active region in terms of star formation in the Chamaeleon molecular cloud complex. Although it is one of the nearest low-mass star forming regions, its population of prestellar and protostellar cores is not known and a controversy exists concerning its history of star formation. Our goal is to search for prestellar and protostellar cores and characterize the earliest stages of star formation in this cloud.
- ID:
- ivo://CDS.VizieR/J/MNRAS/400/299
- Title:
- Chandra deep protocluster survey
- Short Name:
- J/MNRAS/400/299
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present X-ray point-source catalogues for a deep ~400ks Chandra ACIS-I (Advanced CCD Imaging Spectrometer) exposure of the SSA22 field. The observations are centred on a z=3.09 protocluster, which is populated by Lyman break galaxies (LBGs), Ly{alpha} emitters (LAEs) and extended Ly{alpha}-emitting blobs (LABs). The survey reaches ultimate (3 count) sensitivity limits of ~5.7x10^-17^ and ~3.0x10^-16^erg/cm^2^/s for the 0.5-2 and 2-8keV bands, respectively (corresponding to L_2-10keV_~5.7x10^42^erg/s and L_10-30keV_~2.0x10^43^erg/s at z=3.09, respectively, for an assumed photon index of {GAMMA}=1.4). These limits make SSA22 the fourth deepest extragalactic Chandra survey yet conducted, and the only one focused on a known high-redshift structure. In total, we detect 297 X-ray point sources and identify one obvious bright extended X-ray source over a ~330arcmin^2^ region. In addition to our X-ray catalogues, we provide all available optical spectroscopic redshifts and near-infrared and mid-infrared photometry available for our sources.
- ID:
- ivo://CDS.VizieR/J/ApJ/833/248
- Title:
- Chemical properties of red MSX sources (RMSs)
- Short Name:
- J/ApJ/833/248
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Red Midcourse Space Experiment (MSX) Sources (RMSs) are regarded as excellent candidates of massive star-forming regions. In order to characterize the chemical properties of massive star formation, we made a systematic study of 87 RMSs in the southern sky, using archival data taken from the Atacama Pathfinder Experiment Telescope Large Area Survey of the Galaxy (ATLASGAL), the Australia Telescope Compact Array, and the Millimetre Astronomy Legacy Team Survey at 90GHz (MALT90). According to previous multiwavelength observations, our sample could be divided into two groups: massive young stellar objects and HII regions. Combined with the MALT90 data, we calculated the column densities of N_2_H^+^, C_2_H, HC_3_N, and HNC and found that they are not much different from previous studies made in other massive star-forming regions. However, their abundances are relatively low compared to infrared dark clouds (IRDCs). The abundances of N_2_H^+^ and HNC in our sample are at least 1mag lower than those found in IRDCs, indicating chemical depletions in the relatively hot gas. Besides, the fractional abundances of N_2_H^+^, C_2_H, and HC_3_N seem to decrease as a function of their Lyman continuum fluxes (N_L_), indicating that these molecules could be destroyed by UV photons when HII regions have formed inside. We also find that the C_2_H abundance decreases faster than HC_3_N with respect to N_L_. The abundance of HNC has a tight correlation with that of N_2_H^+^, indicating that it may be also preferentially formed in cold gas. We regard our RMSs as being in a relatively late evolutionary stage of massive star formation.
- ID:
- ivo://CDS.VizieR/J/ApJ/846/105
- Title:
- [CII], [OI] and [OIII] line emission from z~6 gal.
- Short Name:
- J/ApJ/846/105
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Of the almost 40 star-forming galaxies at z>~5 (not counting quasi-stellar objects) observed in [CII] to date, nearly half are either very faint in [CII] or not detected at all, and fall well below expectations based on locally derived relations between star formation rate and [CII] luminosity. This has raised questions as to how reliable [CII] is as a tracer of star formation activity at these epochs and how factors such as metallicity might affect the [CII] emission. Combining cosmological zoom simulations of galaxies with SIGAME (SImulator of GAlaxy Millimeter/submillimeter Emission), we modeled the multiphased interstellar medium (ISM) and its emission in [CII], as well as in [OI] and [OIII], from 30 main-sequence galaxies at z~6 with star formation rates ~3-23M_{sun}_/yr, stellar masses ~(0.7-8)x10^9^M_{sun}_, and metallicities ~(0.1-0.4)xZ_{sun}_. The simulations are able to reproduce the aforementioned [CII] faintness of some normal star-forming galaxy sources at z>=5. In terms of [OI] and [OIII], very few observations are available at z>~5, but our simulations match two of the three existing z>~5 detections of [OIII] and are furthermore roughly consistent with the [OI] and [OIII] luminosity relations with star formation rate observed for local starburst galaxies. We find that the [CII] emission is dominated by the diffuse ionized gas phase and molecular clouds, which on average contribute ~66% and ~27%, respectively. The molecular gas, which constitutes only ~10% of the total gas mass, is thus a more efficient emitter of [CII] than the ionized gas, which makes up ~85% of the total gas mass. A principal component analysis shows that the [CII] luminosity correlates with the star formation activity of a galaxy as well as its average metallicity. The low metallicities of our simulations together with their low molecular gas mass fractions can account for their [CII] faintness, and we suggest that these factors may also be responsible for the [CII]-faint normal galaxies observed at these early epochs.
- ID:
- ivo://CDS.VizieR/J/MNRAS/449/574
- Title:
- Circumstellar discs at white dwarfs
- Short Name:
- J/MNRAS/449/574
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- White dwarfs whose atmospheres are polluted by terrestrial-like planetary debris have become a powerful and unique tool to study evolved planetary systems. This paper presents results for an unbiased Spitzer Infrared Array Camera search for circumstellar dust orbiting a homogeneous and well-defined sample of 134 single white dwarfs. The stars were selected without regard to atmospheric metal content but were chosen to have (1) hydrogen-rich atmospheres, (2) 17000<Teff<25000K and correspondingly young post-main-sequence ages of 15-270Myr, and (3) sufficient far-ultraviolet brightness for a corresponding Hubble Space Telescope COS snapshot. Five white dwarfs were found to host an infrared bright dust disc, three previously known, and two reported here for the first time, yielding a nominal 3.7^+2.4^_-1.0_ percent of white dwarfs in this post-main-sequence age range with detectable circumstellar dust. Remarkably, the complementary Hubble observations indicate that a fraction of 27 percent show metals in their photosphere that can only be explained with ongoing accretion from circumstellar material, indicating that nearly 90 percent of discs escape detection in the infrared, likely due to small emitting surface area. This paper also presents the distribution of disc fractional luminosity as a function of cooling age for all known dusty white dwarfs, suggesting possible disc evolution scenarios and indicating an undetected population of circumstellar discs.
- ID:
- ivo://CDS.VizieR/J/ApJ/784/62
- Title:
- Circumstellar disks around binary stars in Taurus
- Short Name:
- J/ApJ/784/62
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have conducted a survey of 17 wide (>100 AU) young binary systems in Taurus with the Atacama Large Millimeter Array (ALMA) at two wavelengths. The observations were designed to measure the masses of circumstellar disks in these systems as an aid to understanding the role of multiplicity in star and planet formation. The ALMA observations had sufficient resolution to localize emission within the binary system. Disk emission was detected around all primaries and 10 secondaries, with disk masses as low as 10^-4^ M_{sun}_. We compare the properties of our sample to the population of known disks in Taurus and find that the disks from this binary sample match the scaling between stellar mass and millimeter flux of F_mm_ \propto M_*_^1.5-2.0^ to within the scatter found in previous studies. We also compare the properties of the primaries to those of the secondaries and find that the secondary/primary stellar and disk mass ratios are not correlated; in three systems, the circumsecondary disk is more massive than the circumprimary disk, counter to some theoretical predictions.
