- ID:
- ivo://CDS.VizieR/J/A+A/652/A2
- Title:
- rho Oph region revisited with Gaia EDR3
- Short Name:
- J/A+A/652/A2
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Young and embedded stellar populations are important probes of the star formation process. Their properties and the environments they create have the potential to affect the formation of new planets. Paradoxically, we have a better census of nearby embedded young populations than of the slightly more evolved optically visible young populations. The high accuracy measurements and all-sky coverage of Gaia data are about to change this situation. This work aims to construct the most complete sample to date of YSOs in the {rho} Oph region. We compile a catalog of 1114 Ophiuchus YSOs from the literature and crossmatch it with the Gaia EDR3, Gaia-ESO, and APOGEE-2 surveys. We apply a multivariate classification algorithm to this catalog to identify new, co- moving population candidates. We find 191 high-fidelity new YSO candidates in the Gaia EDR3 catalog belonging to the {rho} Oph region. The new sources appear to be mainly Class III M-stars and substellar objects and are less extincted than the known members, while we find that 28 of previously unknown sources are YSOs with circumstellar disks (Class I or Class II). The analysis of the proper motion distribution of the entire sample reveals a well-defined bimodality, implying two distinct populations sharing a similar 3D volume. The first population comprises young stars' clusters around the {rho} Ophiuchi star and the main Ophiuchus clouds (L1688, L1689, L1709). In contrast, the second population is slightly older (~10Myr), more dispersed, has a distinct proper motion, and is possibly from the Upper-Sco group. The two populations are moving away from each other at about 4.1km/s and will no longer overlap in about 4Myr. Finally, we flag 17 sources in the literature sample as likely impostors, which are sources that exhibit large deviations from the average properties of the {rho} Oph population. Our results show the importance of accurate 3D space and motion information for improved stellar population analysis.
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- ID:
- ivo://CDS.VizieR/J/MNRAS/437/1791
- Title:
- RMS survey: molecular observations
- Short Name:
- J/MNRAS/437/1791
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used the well-selected sample of ~1750 embedded, young, massive stars identified by the Red MSX Source (RMS) survey to investigate the Galactic distribution of recent massive star formation. We present molecular line observations for ~800 sources without existing radial velocities. We describe the various methods used to assign distances extracted from the literature and solve the distance ambiguities towards approximately 200 sources located within the solar circle using archival Hi data. These distances are used to calculate bolometric luminosities and estimate the survey completeness (~2x10^4^L_{sun}_). In total, we calculate the distance and luminosity of ~1650 sources, one third of which are above the survey's completeness threshold. Examination of the sample's longitude, latitude, radial velocities and mid-infrared images has identified ~120 small groups of sources, many of which are associated with well-known star formation complexes, such as G305, G333, W31, W43, W49 and W51. We compare the positional distribution of the sample with the expected locations of the spiral arms, assuming a model of the Galaxy consisting of four gaseous arms. The distribution of young massive stars in the Milky Way is spatially correlated with the spiral arms, with strong peaks in the source position and luminosity distributions at the arms' Galactocentric radii. The overall source and luminosity surface densities are both well correlated with the surface density of the molecular gas, which suggests that the massive star formation rate per unit molecular mass is approximately constant across the Galaxy. A comparison of the distribution of molecular gas and the young massive stars to that in other nearby spiral galaxies shows similar radial dependences. We estimate the total luminosity of the embedded massive star population to be ~0.76x10^8^L_{sun}_, 30 per cent of which is associated with the 10 most active star-forming complexes. We measure the scaleheight as a function of the Galactocentric distance and find that it increases only modestly from ~20-30pc between 4 and 8kpc, but much more rapidly at larger distances.
- ID:
- ivo://CDS.VizieR/J/A+A/513/A38
- Title:
- RZJHK photometry for stellar sources in Serpens
- Short Name:
- J/A+A/513/A38
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a deep optical/near-infrared imaging survey of the Serpens molecular cloud. This survey constitutes the complementary optical data to the Spitzer "Core To Disk" (c2d) Legacy survey in this cloud. The survey was conducted using the Wide Field Camera at the Isaac Newton Telescope. About 0.96 square degrees were imaged in the R and Z filters, covering the entire region where most of the young stellar objects identified by the c2d survey are located. 26524 point-like sources were detected in both R and Z bands down to R=24.5mag and Z=23mag with a signal-to-noise ratio better than 3. The 95% completeness limit of our catalog corresponds to 0.04 solar masses for members of the Serpens star forming region (age 2Myr and distance 260pc) in the absence of extinction. Adopting the typical extinction of the observed area (Av=7mag), we estimate a 95% completeness level down to 0.1 solar masses. The astrometric accuracy of our catalog is 0.4-arcsec with respect to the 2MASS catalog. Our final catalog contains J2000 celestial coordinates, magnitudes in the R and Z bands calibrated to the SDSS photometric system and, where possible, JHK magnitudes from 2MASS for sources in 0.96 square degrees in the direction of Serpens. This data product has been already used within the frame of the c2d Spitzer Legacy Project analysis in Serpens to study the star/disk formation and evolution in this cloud; here we use it to obtain new indications of the disk-less population in Serpens.
- ID:
- ivo://CDS.VizieR/J/A+A/609/A123
- Title:
- SABOCA imaging of G304.74+01.32
- Short Name:
- J/A+A/609/A123
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We aim to determine the occurrence of fragmentation into cores in the clumps of the filamentary IRDC G304.74+01.32. We also aim to determine the basic physical characteristics of the clumps and cores in G304.74. We mapped the G304.74 filament at 350 micron using the SABOCA bolometer. The new SABOCA data have a factor of 2.2 times higher resolution than our previous LABOCA 870 micron map of the cloud (9" versus 19.86"). We also employed the Herschel far-IR and submillimetre, and WISE IR imaging data available for G304.74. The WISE data allowed us to trace the IR emission of the YSOs associated with the cloud. The SABOCA 350 micron data show that G304.74 is composed of a dense filamentary structure with a mean width of only 0.18+/-0.05pc. The percentage of LABOCA clumps that are found to be fragmented into SABOCA cores is 36%+/-16%, but the irregular morphology of some of the cores suggests that this multiplicity fraction could be higher. The WISE data suggest that 65%+/-18% of the SABOCA cores host YSOs. The mean dust temperature of the clumps, derived by comparing the Herschel 250, 350, and 500 micron flux densities, was found to be 15.0+/-0.8K. The mean mass, beam-averaged H_2_ column density, and H_2_ number density of the LABOCA clumps are estimated to be 55+/-10M_{sun}_, (2.0+/-0.2)x10^22^cm^-2^, and (3.1+/-0.2)x10^4^cm^-3^. The corresponding values for the SABOCA cores are 29+/-3M_{sun}_, (2.9+/-0.3)x10^22^cm^-2^, and (7.9+/-1.2)x10^4^cm^-3^. The G304.74 filament is estimated to be thermally supercritical by a factor of >~3.5 on the scale probed by LABOCA, and by a factor of >~1.5 for the SABOCA filament. Our data strongly suggest that the IRDC G304.74 has undergone hierarchical fragmentation. On the scale where the clumps have fragmented into cores, the process can be explained in terms of gravitational Jeans instability. Besides the filament being fragmented, the finding of embedded YSOs in G304.74 indicates its thermally supercritical state, although the potential non-thermal (turbulent) motions can render the cloud a virial equilibrium system on scale traced by LABOCA. The IRDC G304.74 has a seahorse-like morphology in the Herschel images, and the filament appears to be attached by elongated, perpendicular striations. This is potentially evidence that G304.74 is still accreting mass from the surrounding medium, and the accretion process can contribute to the dynamical evolution of the main filament. One of the clumps in G304.74, IRAS 13039-6108, is already known to be associated with high-mass star formation, but the remaining clumps and cores in this filament might preferentially form low and intermediate-mass stars owing to their mass reservoirs and sizes. Besides the presence of perpendicularly oriented, dusty striations and potential embedded intermediate-mass YSOs, G304.74 is a relatively nearby (d~2.5kpc) IRDC, which makes it a useful target for future star formation studies. Owing to its observed morphology, we propose that G304.74 could be nicknamed the Seahorse Nebula. Description: The SABOCA 350 micron and LABOCA 870 micron dust continuum maps of G304.74+01.32. The data were reduced using the CRUSH-2 software
- ID:
- ivo://CDS.VizieR/J/A+A/631/A72
- Title:
- SABOCA 350um view of ATLASGAL-selected massive clumps
- Short Name:
- J/A+A/631/A72
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The structure formation of the dense interstellar material and the fragmentation of clumps into cores is a fundamental step to understand how stars and stellar clusters form. We aim to establish a statistical view of clump fragmentation at sub-parsec scales based on a large sample of massive clumps selected from the ATLASGAL survey. We used the APEX/SABOCA camera at 350um to image clumps at a resolution of 8.5", corresponding to physical scales of <0.2pc at a distance <5kpc. The majority of the sample consists of massive clumps that are weak or in absorption at 24um. We resolve spherical and filamentary structures and identify the population of compact sources. Complemented with archival Herschel data, we derive the physical properties, such as dust temperature, mass and bolometric luminosity of clumps and cores. We use association with mid-infrared 22-24 m and 70 m point sources to pin down the star formation activity of the cores. We then statistically assess their physical properties, and the fragmentation characteristics of massive clumps. We detect emission at 350um towards all targets and find that it typically exhibits a filamentary(-like) morphology and hosts a population of compact sources. Using Gaussclumps we identify 1120 compact sources and derive the physical parameters and star formation activity for 971 of these, 874 of which are associated with 444 clumps. We find a moderate correlation between the clump fragmentation levels with the clump gas density and the predicted number of fragments with pure Jeans fragmentation scenario. We find a strong correlation between the mass of the most massive fragment and the total clump mass, suggesting that the self-gravity may play an important role in the clumps' small scale structure formation. Finally, due to the improved angular resolution compared to ATLASGAL, we are able to identify 27 massive quiescent cores with M_core_>100M_{sun}_ within 5kpc; these are massive enough to be self-gravitating but do not yet show any sign of star-formation. This sample comprises, therefore, promising candidates of massive pre-stellar cores, or deeply embedded high-mass protostars. The submillimeter observations of the massive clumps that are weak or completely dark at 24um reveal rich filamentary structures and an embedded population of compact cores. The maximum core mass is likely determined by the self-gravity of the clump. The rarity of massive pre-stellar core candidates implies short collapse time-scales for dense structures.
- ID:
- ivo://CDS.VizieR/J/ApJ/653/383
- Title:
- SCUBA observations in Orion A South region
- Short Name:
- J/ApJ/653/383
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from a 2300arcmin^2^ survey of the Orion A molecular cloud at 450 and 850um using the Submillimeter Common-User Bolometer Array (SCUBA) on the James Clerk Maxwell Telescope. The region mapped lies directly south of the OMC 1 cloud core and includes OMC 4, OMC 5, HH 1/2, HH 34, and L1641N. We identify 71 independent clumps in the 850um map and compute size, flux, and degree of central concentration in each.
- ID:
- ivo://CDS.VizieR/J/ApJ/671/1800
- Title:
- SCUBA observations of {rho} Oph cloud
- Short Name:
- J/ApJ/671/1800
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new multiwavelength submillimeter continuum measurements of the circumstellar dust around 48 young stars in the rho Ophiuchi dark clouds. Supplemented with previous 1.3mm observations of an additional 99 objects from the literature, the statistical distributions of disk masses and submillimeter colors are calculated and compared to those in the Taurus-Auriga region. These basic submillimeter properties of young stellar objects in both environments are shown to be essentially identical.
- ID:
- ivo://CDS.VizieR/J/MNRAS/374/1413
- Title:
- SCUBA survey of Orion
- Short Name:
- J/MNRAS/374/1413
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have re-analysed all of the Submillimetre Common User Bolometer Array (SCUBA) archive data of the Orion star-forming regions. We have put together all of the data taken at different times by different groups. Consequently, we have constructed the deepest submillimetre maps of these regions ever made. There are four regions that have been mapped: Orion A North and South, and Orion B North and South. We find that two of the regions, Orion A North and Orion B North, have deeper sensitivity and completeness limits, and contain a larger number of sources, so we concentrate on these two. We compare the data with archive data from the Spitzer Space Telescope to determine whether or not a core detected in the submillimetre is pre-stellar in nature.
- ID:
- ivo://CDS.VizieR/J/A+A/613/A11
- Title:
- SDC13 NH_3_(1,1) and NH_3_(2,2) datacubes
- Short Name:
- J/A+A/613/A11
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Converging networks of interstellar filaments, that is hubs, have been recently linked to the formation of stellar clusters and massive stars. Understanding the relationship between the evolution of these systems and the formation of cores and stars inside them is at the heart of current star formation research. The goal is to study the kinematic and density structure of the SDC13 prototypical hub at high angular resolution to determine what drives its evolution and fragmentation. We have mapped SDC13, a ~1000M_{sun}_ infrared dark hub, in NH_3_(1,1) and NH_3_(2,2) emission lines, with both the Jansky Very Large Array and Green Bank Telescope. The high angular resolution achieved in the combined dataset allowed us to probe scales down to 0.07pc. After fitting the ammonia lines, we computed the integrated intensities, centroid velocities and line widths, along with gas temperatures and H_2_ column densities. The mass-per-unit-lengths of all four hub filaments are thermally super- critical, consistent with the presence of tens of gravitationally bound cores identified along them. These cores exhibit a regular separation of ~0.37+/-0.16pc suggesting gravitational instabilities running along these super-critical filaments are responsible for their fragmentation. The observed local increase of the dense gas velocity dispersion towards starless cores is believed to be a consequence of such fragmentation process. Using energy conservation arguments, we estimate that the gravitational to kinetic energy conversion efficiency in the SDC13 cores is ~35%. We see velocity gradient peaks towards ~63% of cores as expected during the early stages of filament fragmentation. Another clear observational signature is the presence of the most massive cores at the filaments' junction, where the velocity dispersion is largest. We interpret this as the result of the hub morphology generating the largest acceleration gradients near the hub centre. We propose a scenario for the evolution of the SDC13 hub in which filaments first form as post-shock structures in a supersonic turbulent flow. As a result of the turbulent energy dissipation in the shock, the dense gas within the filaments is initially mostly subsonic. Then gravity takes over and starts shaping the evolution of the hub, both fragmenting filaments and pulling the gas towards the centre of the gravitational well. By doing so, gravitational energy is converted into kinetic energy in both local (cores) and global (hub centre) potential well minima. Furthermore, the generation of larger gravitational acceleration gradients at the filament junctions promotes the formation of more massive cores.
- ID:
- ivo://CDS.VizieR/J/AJ/124/2164
- Title:
- SDSS photometry in the field of L1457
- Short Name:
- J/AJ/124/2164
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a spectroscopic and photometric survey of a sample of field stars in the region of the molecular cloud L1457. High-quality coude feed spectra, together with five-band photometry in the Sloan Digital Sky Survey system and near-infrared archival data from the Two Micron All Sky Survey, are used to derive color excesses and distances for the stars. Based on these data, a new distance estimate of 360+/-30pc is derived for the cloud, supporting recent results by K.L. Luhman, 2001ApJ...560..287L. The data further indicate that the north-south velocity gradient seen in the millimeter-wave CO data is mirrored in a distance gradient, with the northern part of the cloud being closer to us. A second, less opaque, layer of extinction is detected at ~80pc. This distance is consistent with the earlier distance estimates to the cloud, based on Na I absorption. We identify this layer with the wall of the hot Local Bubble. Hence, the dense cloud is not, as previously thought, associated with the Local Bubble.
