- ID:
- ivo://CDS.VizieR/J/MNRAS/484/4444
- Title:
- ATLASGAL dense clumps Molecular parameters
- Short Name:
- J/MNRAS/484/4444
- Date:
- 10 Dec 2021 00:02:11
- Publisher:
- CDS
- Description:
- We have conducted a 3-mm molecular-line survey towards 570 high-mass star-forming clumps, using the Mopra telescope. The sample is selected from the 10000 clumps identified by the ATLASGAL (APEX Telescope Large Area Survey of the Galaxy) survey and includes all of the most important embedded evolutionary stages associated with massive star formation, classified into five distinct categories (quiescent, protostellar, young stellar objects, HII regions, and photon-dominated regions). The observations were performed in broad-band mode with frequency coverage of 85.2-93.4GHz and a velocity resolution of ~0.9km/s, detecting emission from 26 different transitions. We find significant evolutionary trends in the detection rates, integrated line intensities, and abundances of many of the transitions and also identify a couple of molecules that appear to be invariant to changes in the dust temperature and evolutionary stage [N_2_H^+^ (1-0) and HN^13^C (1-0)]. We use the K-ladders for CH_3_C_2_H (5-4) and CH_3_CH (5-4) to calculate the rotation temperatures and find around one-third of the quiescent clumps have rotation temperatures that suggest the presence of an internal heating source. These sources may constitute a population of very young protostellar objects that are still dark at 70um and suggest that the fraction of truly quiescent clumps may only be a few per cent. We also identify a number of line ratios that show a strong correlation with the evolutionary stage of the embedded objects and discuss their utility as diagnostic probes of evolution.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/159/15
- Title:
- Binary stars in Upper Scorpius
- Short Name:
- J/AJ/159/15
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To address the statistics of binary stars in the 8 Myr old Upper Scorpius (USco) star formation region, we conducted a speckle interferometric survey of 614 association members more massive than 0.4 M_{sun}_ (spectral types earlier than M3V) based on the list of Luhman et al. (2018, J/AJ/156/271). We resolved 187 pairs, 55 of which are new discoveries. Also using the published data and the Gaia DR2 (Cat. I/345), a catalog of 250 physical binaries was produced. We carefully estimated detection limits for each target and studied binary statistics in the separation range from 0.06" to 20" (9-2800 au), as well as clustering at larger separations. The frequency of companions with mass ratios q>0.3 in this separation range is 0.33+/-0.04 and 0.35+/-0.04 for early M- and solar-type stars, respectively, larger by 1.62+/-0.22 and 1.39+/-0.18 times compared to field stars of similar masses. The excess is produced mostly by pairs closer than 100 au. At separations from 100 to 10^4^ au, the separation distribution and companion fraction resemble those of solar-type stars in the field. However, unlike in the field, we see a relative deficit of equal-mass binaries at separations of ~500 au, compared to smaller and larger separations. The distribution of q depends on the separation, with a preference of larger q and a larger fraction of twins with q>0.95 at smaller separations. The binary population of USco differs from binaries in the field in several ways and suggests that binary statistics is not universal.
- ID:
- ivo://CDS.VizieR/J/AJ/158/235
- Title:
- Candidate X-ray sources in IRAS 09002-4732 region
- Short Name:
- J/AJ/158/235
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- IRAS 09002-4732 is a poorly studied embedded cluster of stars in the Vela Molecular Ridge at a distance of 1.7 kpc. Deep observations with the Chandra X-ray Observatory, combined with existing optical and infrared surveys, produce a catalog of 441 probable pre-main-sequence members of the region. The stellar spatial distribution has two components: most stars reside in a rich, compact, elliptical cluster, but a minority reside within a molecular filament several parsecs long that straddles the cluster. The filament has active distributed star formation with dozens of unclustered protostars. The cluster pre-main-sequence population is =<0.8 Myr old and deeply embedded; its most massive member is extremely young, producing an ultracompact H II region. The cluster total population deduced from the X-ray luminosity function is surprisingly rich, twice that of the Orion Nebula Cluster. The cluster core is remarkably dense where strong N-body interactions should be occurring; its initial mass function may be deficient in massive stars. We infer that IRAS 09002-4732 is a rare case where a rich cluster is forming today in a molecular filament, consistent with astrophysical models of cluster formation in clouds that involve the hierarchical formation and merging of groups in molecular filaments.
- ID:
- ivo://CDS.VizieR/J/AJ/155/190
- Title:
- Carina Nebula hot stars: stellar parameters and RVs
- Short Name:
- J/AJ/155/190
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Carina Nebula is an active star-forming region in the southern sky that is of particular interest due to the presence of a large number of massive stars in a wide array of evolutionary stages. Here, we present the results of the spectroscopic analysis of 82 B-type stars and 33 O-type stars that were observed in 2013 and 2014. For 82 B-type stars without line blending, we fit model spectra from the Tlusty BSTAR2006 grid to the observed profiles of H{gamma} and He {lambda}{lambda}4026, 4388, and 4471 to measure the effective temperatures, surface gravities, and projected rotational velocities. We also measure the masses, ages, radii, bolometric luminosities, and distances of these stars. From the radial velocities measured in our sample, we find 31 single lined spectroscopic binary candidates. We find a high dispersion of radial velocities among our sample stars, and we argue that the Carina Nebula stellar population has not yet relaxed and become virialized.
- ID:
- ivo://CDS.VizieR/J/AJ/154/152
- Title:
- CARMA 1 cm spectral line survey of Orion-KL
- Short Name:
- J/AJ/154/152
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Orion-KL is a well-known high-mass star-forming region that has long been the target of spectral line surveys and searches for complex molecules. One spectral window where the region had never been surveyed is around wavelengths of {lambda}=1 cm. This is an important window to observe, due to the fundamental and low energy transitions of numerous complex molecules that indicate the maximum spatial extent of the molecular species; knowing the spatial distribution of a molecule aids in determining the formation mechanism(s) of that molecule. Additionally, there are fewer transitions in this window, reducing confusion caused by blended lines that can be very problematic at shorter wavelengths ({lambda}<3 mm). In this work, we present the first spectral line survey at {lambda}=1 cm of the Orion-KL region. A total of 89 transitions were detected from 14 molecular species and isotopologues, and two atomic species. The observations were conducted with the Combined Array for Research in Millimeter-wave Astronomy in both interferometric and single dish modes.
- ID:
- ivo://CDS.VizieR/J/AJ/162/52
- Title:
- Census of variable stars toward Serpens Main
- Short Name:
- J/AJ/162/52
- Date:
- 14 Mar 2022 06:55:43
- Publisher:
- CDS
- Description:
- We monitored a 3deg^2^ area toward Serpens Main in the Pan-STARRS1 r, i, and z bands from 2016 April to September. Light curves of more than 11000 stars in each band were obtained, and 143 variables have been identified. Among those, 119 variables are new discoveries, while 24 variables were previously known. We present variability classes and periods of 99 stars. Of these, 81 are located in the upper giant branch, displaying long periods, while the remaining 18 variables are pre-main-sequence objects with short periods. We also identify eight eclipsing binary systems, including the known binary V0623Ser, and derive their physical parameters. According to a clustering analysis of Gaia DR2 stars in the observed field, there are 10 variable members in Serpens Main, where six members have been classified as young stellar objects in previous studies. Here we provide color-magnitude and color-color diagrams for these variables. The color variability of most variables in the color-magnitude diagrams produces the expected displacements, while the movements of cluster members point in different directions; this behavior may be associated with accretion spots or circumstellar disks.
- ID:
- ivo://CDS.VizieR/J/ApJ/888/118
- Title:
- Chandra and IR study toward IRAS 16562-3959
- Short Name:
- J/ApJ/888/118
- Date:
- 17 Jan 2022 11:46:14
- Publisher:
- CDS
- Description:
- We present the results from Chandra X-ray observations, and near- and mid-infrared analysis, using VISTA/VVV and Spitzer/GLIMPSE catalogs, of the high-mass star-forming region IRAS 16562-3959, which contains a candidate for a high-mass protostar. We detected 249 X-ray sources within the ACIS-I field of view. The majority of the X-ray sources have low count rates (<0.638cts/ks) and hard X-ray spectra. The search for YSOs in the region using VISTA/VVV and Spitzer/GLIMPSE catalogs resulted in a total of 636 YSOs, with 74 Class I and 562 Class II YSOs. The search for near- and mid-infrared counterparts of the X-ray sources led to a total of 165 VISTA/VVV counterparts, and a total of 151 Spitzer/GLIMPSE counterparts. The infrared analysis of the X-ray counterparts allowed us to identify an extra 91 Class III YSOs associated with the region. We conclude that a total of 727 YSOs are associated with the region, with 74 Class I, 562 Class II, and 91 Class III YSOs. We also found that the region is composed of 16 subclusters. In the vicinity of the high-mass protostar, the stellar distribution has a core-halo structure. The subcluster containing the high-mass protostar is the densest and the youngest in the region, and the high-mass protostar is located at its center. The YSOs in this cluster appear to be substantially older than the high-mass protostar.
- ID:
- ivo://CDS.VizieR/J/AJ/155/241
- Title:
- Chandra X-ray detection of YSOs in Serpens South
- Short Name:
- J/AJ/155/241
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a Chandra study of the deeply embedded Serpens South star-forming region, examining cluster structure and disk properties at the earliest stages. In total, 152 X-ray sources are detected. Combined with Spitzer and 2MASS photometry, 66 X-ray sources are reliably matched to an IR counterpart. We identify 21 class I, 6 flat spectrum, 16 class II, and 18 class III young stars; 5 were unclassified. Eighteen sources were variable in X-rays, 8 exhibiting flare-like emission and one source being periodic. The cluster's X-ray luminosity distance was estimated: the best match was to the nearer distance of 260 pc for the front of the Aquila Rift complex. The ratio of N_H_ to A_K_ is found to be ~0.68x10^22^, similar to that measured in other young low-mass regions, but lower than that measured in the interstellar medium and high-mass clusters (~(1.6-2)x10^22^). We find that the spatial distribution closely follows that of the dense filament from which the stars have formed, with the class II population still strongly associated with the filament. There are four subclusters in the field, with three forming knots in the filament, and a fourth to the west, which may not be associated but may be contributing to the distributed class III population. A high percentage of diskless class IIIs (upper limit 30% of classified X-ray sources) in such a young cluster could indicate that processing of disks is influenced by the cluster environment and is not solely dependent on timescale.
- ID:
- ivo://CDS.VizieR/J/A+A/642/A86
- Title:
- Circumstellar disks in Lupus complex
- Short Name:
- J/A+A/642/A86
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Previous star formation studies have, out of necessity, often defined a population of young stars confined to the proximity of a molecular cloud. Gaia allows us to examine a wider, three-dimensional structure of nearby star forming regions, leading to a new understanding of their history. We present a wide-area survey covering 494 deg^2^ of the Lupus complex, a prototypical low-mass star forming region. Our survey includes all known molecular clouds in this region as well as parts of the Upper Scorpius and Upper Centaurus Lupus (UCL) groups of the Sco-Cen complex. We combine Gaia DR2 proper motions and parallaxes as well as ALLWISE mid-infrared photometry to select young stellar objects (YSOs) with disks. The YSO ages are inferred from Gaia color-magnitude diagrams, and their evolutionary stages from the slope of the spectral energy distributions. We find 98 new disk-bearing sources. Our new sample includes objects with ages ranging from 1 to 15Myr and masses ranging from 0.05 to 0.5M_{sun}_, and consists of 56 sources with thick disks and 42 sources with anemic disks. While the youngest members are concentrated in the clouds and at distances of 160 pc, there is a distributed population of slightly older stars that overlap in proper motion, spatial distribution, distance, and age with the Lupus and UCL groups. The spatial and kinematic properties of the new disk-bearing YSOs indicate that Lupus and UCL are not distinct groups. Our new sample comprises some of the nearest disks to Earth at these ages, and thus provides an important target for follow-up studies of disks and accretion in very low mass stars, for example with ALMA and ESO-VLT X-shooter.
- ID:
- ivo://CDS.VizieR/J/AJ/157/196
- Title:
- Close companions around young stars
- Short Name:
- J/AJ/157/196
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Multiplicity is a fundamental property that is set early during stellar lifetimes, and it is a stringent probe of the physics of star formation. The distribution of close companions around young stars is still poorly constrained by observations. We present an analysis of stellar multiplicity derived from Apache Point Observatory Galactic Evolution Experiment-2 spectra obtained in targeted observations of nearby star-forming regions. This is the largest homogeneously observed sample of high-resolution spectra of young stars. We developed an autonomous method to identify double-lined spectroscopic binaries (SB2s). Out of 5007 sources spanning the mass range of ~0.05-1.5 M_{sun}_, we find 399 binaries, including both radial velocity (RV) variables and SB2s. The mass ratio distribution of SB2s is consistent with being uniform for q<0.95 with an excess of twins for q>0.95. The period distribution is consistent with what has been observed in close binaries (<10 au) in the evolved populations. Three systems are found to have q~0.1, with a companion located within the brown dwarf desert. There are no strong trends in the multiplicity fraction as a function of cluster age from 1 to 100 Myr. There is a weak dependence on stellar density, with companions being most numerous at {Sigma}_*_~30 stars/pc^-2^ and decreasing in more diffuse regions. Finally, disk-bearing sources are deficient in SB2s (but not RV variables) by a factor of ~2; this deficit is recovered by the systems without disks. This may indicate a quick dispersal of disk material in short-period equal-mass systems that is less effective in binaries with lower q.
