- ID:
- ivo://CDS.VizieR/J/AJ/128/1233
- Title:
- LkH{alpha} 101 and the young cluster in NGC 1579
- Short Name:
- J/AJ/128/1233
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The central region of the dark cloud L1482 is illuminated by LkH{alpha} 101, a heavily reddened (A_V_~10mag) high-luminosity (>=8x10^3^L_Sun_) star having an unusual emission-line spectrum plus a featureless continuum. About 35 much fainter (mostly between R=16 and >21) H{alpha} emitters have been found in the cloud. Their color-magnitude distribution suggests a median age of about 0.5Myr, with considerable dispersion. There are also at least five bright B-type stars in the cloud, presumably of about the same age; none show the peculiarities expected of HAeBe stars. Dereddened, their apparent V magnitudes lead to a distance of about 700pc. Radio observations suggest that the optical object LkH{alpha} 101 is in fact a hot star surrounded by a small H II region, both inside an optically thick dust shell.
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462. LMC extended catalog
- ID:
- ivo://CDS.VizieR/J/AJ/117/238
- Title:
- LMC extended catalog
- Short Name:
- J/AJ/117/238
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A survey of extended objects in the Large Magellanic Cloud was carried out on the ESO/SERC R and J Sky Survey Atlases, checking entries in previous catalogs and searching for new objects. The census provided 6659 objects including star clusters, emission-free associations, and objects related to emission nebulae. Each of these classes contains three subclasses with intermediate properties, which are used to infer total populations. The survey includes cross identifications among catalogs, and we present 3246 new objects. We provide accurate positions, classification, and homogeneous measurements of sizes and position angles, as well as information on cluster pairs and hierarchical relation for superimposed objects. This unification and enlargement of catalogs is important for future searches of fainter and smaller new objects. We discuss the angular and size distributions of the objects of the different classes. The angular distributions show two off-centered systems with different inclinations, suggesting that the LMC disk is warped. The present catalog together with its previous counterpart for the SMC and the inter-Cloud region provide a total population of 7847 extended objects in the Magellanic System. The angular distribution of the ensemble reveals important clues on the interaction between the LMC and SMC.
- ID:
- ivo://CDS.VizieR/J/AJ/116/723
- Title:
- LMC star clusters ages and metallicity
- Short Name:
- J/AJ/116/723
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Washington system CT_1_ color-magnitude diagrams of 13 star clusters and their surrounding fields that lie in the outer parts of the LMC disk (r>4{deg}), as well as a comparison inner cluster. The total area covered is large (2/3deg^2^), allowing us to study the clusters and their fields individually and in the context of the entire Galaxy. Ages are determined by means of the magnitude difference {delta}T_1_ between the giant branch clump and the turnoff, while metallicities are derived from the location of the giant and subgiant branches as compared with fiducial star clusters. This yields a unique data set in which ages and metallicities for both a significant sample of clusters and their fields are determined homogeneously. We find that in most cases the stellar population of each star cluster is quite similar to that of the field where it is embedded, sharing its mean age and metallicity. The old population (t>=10Gyr) is detected in most fields as a small concentration of stars on the horizontal branch blueward and faintward of the prominent clump.
- ID:
- ivo://CDS.VizieR/J/A+A/405/111
- Title:
- LMC Survey of Young Stellar Systems
- Short Name:
- J/A+A/405/111
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The method developed by Gouliermis et al. (2000AJ....119.1737G), for the detection and classification of stellar systems in the LMC, was used for the identification of stellar associations and open clusters in the central area of the LMC. This method was applied on the stellar catalog produced from a scanned 1.2m UK Schmidt Telescope Plate in U with a field of view almost 6.5degx6.5deg, centered on the Bar of this galaxy. The survey of the identified systems is presented here followed by the results of the investigation on their spatial distribution and their structural parameters, as were estimated according to our proposed methodology. The detected open clusters and stellar associations show to form large filamentary structures, which are often connected with the loci of HI shells. The derived mean size of the stellar associations in this survey was found to agree with the average size found previously by other authors, for stellar associations in different galaxies. This common size of about 80pc might represent a universal scale for the star formation process, whereas the parameter correlations of the detected loose systems support the distinction between open clusters and stellar associations.
- ID:
- ivo://CDS.VizieR/J/AJ/158/122
- Title:
- Local structure & star formation history of the MW
- Short Name:
- J/AJ/158/122
- Date:
- 09 Mar 2022 22:00:00
- Publisher:
- CDS
- Description:
- Gaia DR2 (Cat. I/345) provides unprecedented precision in measurements of the distance and kinematics of stars in the solar neighborhood. Through applying unsupervised machine learning on DR2's 5D data set (3D position + 2D velocity), we identify a number of clusters, associations, and comoving groups within 1 kpc and |b|<30{deg} (many of which have not been previously known). We estimate their ages with the precision of ~0.15 dex. Many of these groups appear to be filamentary or string-like, oriented in parallel to the Galactic plane, and some span hundreds of parsec in length. Most of these string lack a central cluster, indicating that their filamentary structure is primordial, rather than the result of tidal stripping or dynamical processing. The youngest strings (<100 Myr) are orthogonal to the Local Arm. The older ones appear to be remnants of several other arm-like structures that cannot be presently traced by dust and gas. The velocity dispersion measured from the ensemble of groups and strings increase with age, suggesting a timescale for dynamical heating of ~300 Myr. This timescale is also consistent with the age at which the population of strings begins to decline, while the population in more compact groups continues to increase, suggesting that dynamical processes are disrupting the weakly bound string populations, leaving only individual clusters to be identified at the oldest ages. These data shed a new light on the local galactic structure and a large-scale cloud collapse.
- ID:
- ivo://CDS.VizieR/J/ApJS/134/103
- Title:
- Low-mass members of IC 2391
- Short Name:
- J/ApJS/134/103
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have identified a large sample of probable low-mass members of the young open cluster IC 2391 based on optical (VRIZ) and infrared (JHKs) photometry. Our sample includes 50 probable members and 82 possible members, both very low-mass stars and brown dwarfs. We also provide accurate positions for these stars and brown dwarf candidates derived from red UK Schmidt plates measured using the microdensitometer SuperCOSMOS. Assuming an age of 53Myr, we estimate that we have reached a mass of 0.025M_{sun}_, if the identified objects are indeed members of IC 2391.
- ID:
- ivo://CDS.VizieR/J/AJ/131/3016
- Title:
- Low-mass objects in Upper Scorpius
- Short Name:
- J/AJ/131/3016
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a wide-field photometric survey covering ~200^{deg}^2 toward the Upper Scorpius OB association. Data taken in the R and I bands with the Quest-2 camera on the Palomar 48inch (1.2m) telescope were combined with the Two Micron All Sky Survey JHK_S_ survey and used to select candidate pre-main-sequence stars. Follow-up spectroscopy with the Palomar 200inch (5.1m) telescope of 62 candidate late-type members identified 43 stars that have surface gravity signatures consistent with association membership.
- ID:
- ivo://CDS.VizieR/J/ApJ/688/377
- Title:
- Low-mass objects in Upper Scorpius. II.
- Short Name:
- J/ApJ/688/377
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present continued results from a wide-field, ~150{deg}^2^, optical photometric and spectroscopic survey of the northern part of the ~5Myr old Upper Scorpius OB association. Photometry and spectral types were used to derive effective temperatures and luminosities and place newly identified association members onto a theoretical Hertzsprung-Russell diagram. From our survey, we have discovered 145 new low-mass members of the association and determined ~10% of these objects to be actively accreting material from a surrounding circumstellar disk.
- ID:
- ivo://CDS.VizieR/J/A+A/471/499
- Title:
- Low-mass stars and brown dwarfs in Blanco 1
- Short Name:
- J/A+A/471/499
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We performed a deep wide field optical survey of the young (~100-150Myr) open cluster Blanco 1 to study its low mass population well down into the brown dwarf regime and estimate its mass function over the whole cluster mass range.
- ID:
- ivo://CDS.VizieR/J/ApJ/646/1215
- Title:
- Low-mass stars and brown dwarfs in NGC 2024
- Short Name:
- J/ApJ/646/1215
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from a near-infrared spectroscopic study of candidate brown dwarfs and low-mass stars in the young cluster NGC 2024. Using FLAMINGOS on the KPNO 2.1m and 4m telescopes, we have obtained spectra of ~70 new members of the cluster and classified them via the prominent J- and H-band water absorption features. Derived spectral types range from ~M1 to later than M8 with typical classification errors of 0.5-1 subclasses. By combining these spectral types with JHK photometry, we place these objects on the H-R diagram and use pre-main-sequence evolutionary models to infer masses and ages. The mean age for this low-mass population of NGC 2024 is 0.5Myr, and derived masses range from ~0.7 to 0.02M_{sun}_ with 23 objects falling below the hydrogen-burning limit. The logarithmic mass function rises to a peak at ~0.2M_{sun}_ before turning over and declining into the substellar regime. There is a possible secondary peak at ~0.035M_{sun}_ ; however, the errors are also consistent with a flat IMF in this region. The ratio of brown dwarfs to stars is similar to that found in the Trapezium but roughly twice the ratio found in IC 348, leading us to conclude that the substellar IMF in young clusters may be dependent on the local star-forming environment.
