- ID:
- ivo://CDS.VizieR/J/ApJ/751/22
- Title:
- Candidates of the {rho} Oph cluster
- Short Name:
- J/ApJ/751/22
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a general method for identifying the pre-main-sequence population of any star-forming region, unbiased with respect to the presence or absence of disks, in contrast to samples selected primarily via their mid-infrared emission from Spitzer surveys. We have applied this technique to a new, deep, wide-field, near-infrared imaging survey of the {rho} Ophiuchi cloud core to search for candidate low-mass members. In conjunction with published Spitzer IRAC photometry and least-squares fits of model spectra (COND, DUSTY, NextGen, and blackbody) to the observed spectral energy distributions, we have identified 948 candidate cloud members within our 90% completeness limits of J=20.0, H=20.0, and Ks=18.50. This population represents a factor of ~3 increase in the number of known young stellar objects in the {rho}} Ophiuchi cloud. A large fraction of the candidate cluster members (81%+/-3%) exhibit infrared excess emission consistent with the presence of disks, thus strengthening the possibility of their being bona fide cloud members. Spectroscopic follow-up will confirm the nature of individual objects, better constrain their parameters, and allow an initial mass function to be derived.
Number of results to display per page
Search Results
- 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/A+A/506/711
- Title:
- Canis Major R1 X-ray sources
- Short Name:
- J/A+A/506/711
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The CMa R1 star-forming region contains several compact clusters as well as many young early-B stars. It is associated with a well-known bright rimmed nebula, the nature of which is unclear (fossil HII region or supernova remnant). To help elucidate the nature of the nebula, our goal was to reconstruct the star-formation history of the CMa R1 region, including the previously unknown older, fainter low-mass stellar population, using X-rays. We analyzed images obtained with the ROSAT satellite, covering ~5deg^2^. Complementary VRI photometry was performed with the Gemini South telescope. Colour-magnitude and colour-colour diagrams were used in conjunction with pre-main sequence evolutionary tracks to derive the masses and ages of the X-ray sources.
- ID:
- ivo://CDS.VizieR/J/A+A/632/A32
- Title:
- Carbon depletion observed inside T Tauri inner rims
- Short Name:
- J/A+A/632/A32
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The carbon content of protoplanetary disks is an important parameter to characterize planets formed at different disk radii. There is some evidence from far-infrared and submillimeter observations that gas in the outer disk is depleted in carbon, with a corresponding enhancement of carbon-rich ices at the disk midplane. Observations of the carbon content inside of the inner sublimation rim could confirm how much cpc on remains locked in kilometer size bodies in the disk. I aim to determine the density, temperature, and carbon abundance inside the disk dust sublimation rim in a set of T Tauri stars with full protoplanetary disks. Using medium-resolution, near-infrared (0.8 to 2.5um) spectra and the new GAIA DR2 distances, I self-consistently determine the stellar, extinction, veiling, and accretion properties of the 26 stars in my sample. From these values, and non-accreting T Tauri spectral templates, I extract the inner disk excess of the target stars from their observed spectra. Then I identify a series of C0 recombination lines in 18 of these disks and use the CHIANTI atomic line database with an optically thin slab model to constrain the average ne, Te, and nC for these lines in the five disks with a complete set of lines. By comparing these values with other slab models of the inner disk using the Cloudy photoionization code, I also constrain nH and the carbon abundance, XC, and hence the amount of carbon 'missing' from the slab. For one disk, DR Tau, I use relative abundances for the accretion stream from the literature to also determine XSi and XN . The inner disks modeled here are extremely dense (nH~10^16^cm^-3^), warm (Te~4500K), and moderately ionized (logXe~3.3). Three of the five modeled disks show robust carbon depletion up to a factor of 42 relative to the solar value. I discuss multiple ways in which the 'missing' carbon could be locked out of the accreting gas. Given the high-density inner disk gas, evidence for radial drift, and lack of obvious gaps in these three systems, their carbon depletion is most consistent with the 'missing' carbon being sequestered in kilometer size bodies. For DR Tau, nitrogen and silicon are also depleted by factors of 45 and 4, respectively, suggesting that the kilometer size bodies into which the grains are locked were formed beyond the N_2_ snowline. I explore briefly what improvements in the models and observations are needed to better address this topic in the future.
- ID:
- ivo://CDS.VizieR/J/A+A/567/A109
- Title:
- Carina nebula optically identified YSOs
- Short Name:
- J/A+A/567/A109
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The low obscuration and proximity of the Carina nebula make it an ideal place to study the ongoing star formation process and impact of massive stars on low-mass stars in their surroundings. To investigate this process, we have generated a new catalogue of the pre-main-sequence (PMS) stars in the Carina west (CrW) region and studied their nature and spatial distribution. We have also determined various parameters (reddening, reddening law, age, mass) which are further used to estimate the initial mass function (IMF) and K-band luminosity function (KLF) for the region under study. We obtained deep UBVRI H{alpha} photometric data of the field situated to the west of the main Carina nebula and centered around WR22. Medium-resolution optical spectroscopy of a subsample of X-ray selected objects along with archival data sets from Chandra, XMM-Newton and 2MASS surveys are used for the present study. Our spectroscopic results indicate that the majority of the X-ray sources are late spectral type stars. The region shows a large amount of differential reddening with minimum and maximum values of E(B-V) as 0.25 and 1.1mag, respectively. Our analysis reveals that the total to selective absorption ratio R_V_ is ~3.7+/-0.1 suggesting an abnormal grain size in the observed region. We identify 467 young stellar objects (YSOs) and study their characteristics. The ages and masses of the 241 optically identified YSOs range from ~0.1 to 10Myr and ~0.3 to 4.8M_{sun}_, respectively. However, the majority of them are younger than 1Myr and have masses below 2M_{sun}_. The high mass star WR22 does not seem to have contributed to the formation of YSOs in the CrW region. The initial mass function slope, Gamma in this region is found to be -1.13+/-0.20 in the mass range of 0.5<M/M_{sun}_<4.8. The K-band luminosity function slope ({alpha}) is also estimated as 0.31+/-0.01. We also performed minimum spanning tree analysis of the YSOs in this region which reveals that there are at least ten YSO cores associated with the molecular cloud and that leads to an average core radius and median branch length 0.43pc and 0.28pc, respectively.
- ID:
- ivo://CDS.VizieR/J/ApJS/123/233
- Title:
- Catalog of Optically selected cores
- Short Name:
- J/ApJS/123/233
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new catalog of 406 dense cores optically selected by using the STScI Digitized Sky Survey (DSS). In this catalog 306 cores have neither an embedded young stellar object (EYSO) nor a pre-main-sequence (PMS) star, 94 cores have EYSOs (one core has both an EYSO and a PMS star), and six cores have PMS stars only. Our sample of dense cores in the catalog is fairly complete within a category of northern Lynds class 5 and 6 clouds and southern Hartley et al. class A clouds, providing a database useful for the systematic study of dense cores. Most of the cores listed in the catalog have diameters between 0.05 and 0.36 pc with a mean of ~0.24pc. The sizes (~0.33pc in the mean) of cores with EYSOs are found to be usually larger than the sizes (~0.22pc in the mean) of starless cores. The typical mean gas density of the cores is ~7x10^3^cm^-3^. Most of the cores are more likely elongated than spherical (mean aspect ratio: ~2.4). The ratio of the number of cores with EYSOs to the number of starless cores for our sample is about 0.3, suggesting that the typical lifetime of starless cores is 0.3-1.6Myr, about 3 times longer than the duration of the class 0 and class I phases. This lifetime is shorter than expected from models of ambipolar diffusion, by factors of 2-44.
- ID:
- ivo://CDS.VizieR/V/112A
- Title:
- Catalog of Star-Forming Regions in the Galaxy
- Short Name:
- V/112A
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This Catalog of Star-Forming Regions in the Galaxy contains coordinates and fluxes of young objects in the radio and infrared, as well as data on the radial velocities of recombination and molecular lines, for more than three thousand star-forming regions. In addition to photometric and kinematic data, we present information on diffuse and reflecting nebulae, dark and molecular clouds, and other objects related to young stars. The catalog consists of two parts. The main catalog lists star-forming regions in order of Galactic longitude and is supplemented by analogous information for star-forming regions in complexes of dark clouds with large angular sizes that are closest to the Sun. In our preliminary study of the catalog data using a formal classification of the star-forming regions, we subdivided these objects into several classes and characterized them as being populated primarily by massive or low-mass stars at early or late stages of the star-formation process. We also distinguish between relatively nearby and distant complexes.
- ID:
- ivo://CDS.VizieR/J/A+AS/115/285
- Title:
- Catalogue of massive young stellar objects
- Short Name:
- J/A+AS/115/285
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A catalogue of massive young stellar objects which contains about 250 objects is presented. This catalogue is an updated version of the catalogue of Henning et al. (1984AN....305...67H). It provides comprehensive information on infrared and radio flux densities, molecular line data, association with maser sources, and outflow phenomena.
- ID:
- ivo://CDS.VizieR/J/A+AS/129/337
- Title:
- CCD photometry of YY Orionis stars
- Short Name:
- J/A+AS/129/337
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Results of photometric monitoring in the UBVRI bands of 5 YY Orionis stars and 2 other variable stars are presented. Each source was observed in the period of 1996, Nov. 23 to Dec. 2 and of 1996, Dec. 23 to 1997,Jan. 2 at the 1-m telescope of Wise Observatory, Israel. Tables.dat contain the luminosity variation of each star as deviation from its average observed magnitude.
- 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.
