- ID:
- ivo://CDS.VizieR/J/A+A/493/931
- Title:
- MAD observations of {sigma} Ori
- Short Name:
- J/A+A/493/931
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Nearby young clusters are privileged places to study the star formation history. Over the last decade, the sigma-Orionis cluster has been a prime location for the study of young very low mass stars, substellar and isolated planetary mass objects and the determination of the initial mass function. To extend previous studies of this association to its core, we searched for ultracool members and new multiple systems within the 1.5'x1.5' central region of the cluster. We obtained deep multi-conjugate adaptive optics (MCAO) images of the core of the sigma-Orionis cluster with the prototype MCAO facility MAD at the VLT using the H and Ks filters. These images allow us to detect companions fainter by DeltaH~5mag as close as 0.2" on a typical source with H=14.5mag. These images were complemented by archival SofI Ks-band images and Spitzer IRAC and MIPS mid-infrared images.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/611/270
- Title:
- Magellanic star clusters IR fluctuations
- Short Name:
- J/ApJ/611/270
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present surface brightness fluctuations (SBFs) in the near-IR for 191 Magellanic star clusters available in the Second Incremental and All Sky Data releases of the Two Micron All Sky Survey (2MASS, Cat. <II/246>) and compare them with SBFs of Fornax Cluster galaxies and with predictions from stellar population models as well.
- ID:
- ivo://CDS.VizieR/J/ApJ/875/51
- Title:
- Mass accretion rates of PMS stars. VI. LH95 in LMC
- Short Name:
- J/ApJ/875/51
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on the accretion properties of low-mass stars in the LH 95 association within the Large Magellanic Cloud. Using noncontemporaneous wideband optical and narrowband H{alpha} photometry obtained with the Hubble Space Telescope, we identify 245 low-mass pre-main-sequence (PMS) candidates showing H{alpha} excess emission above the 4{sigma} level. We derive their physical parameters, including effective temperatures, luminosities, masses (M_*_), ages, accretion luminosities, and mass accretion rates (dM/dt_acc_). We identify two different stellar populations: younger than ~8Myr with median dM/dt_acc_~5.4x10^-8^M_{sun}_/yr (and M_*_~0.15-1.8M_{sun}_) and older than ~8Myr with median dM/dt_acc_~4.8x10^-9^M_{sun}_/yr (and M_*_~0.6-1.2M_{sun}_). We find that the younger PMS candidates are assembled in groups around Be stars, while older PMS candidates are uniformly distributed within the region without evidence of clustering. We find that dM/dt_acc_ in LH 95 decreases with time more slowly than what is observed in Galactic star-forming regions (SFRs). This agrees with the recent interpretation, according to which higher metallicity limits the accretion process in both rate and duration due to higher radiation pressure. The dM/dt_acc_-M_*_ relationship shows different behavior at different ages, becoming progressively steeper at older ages, indicating that the effects of mass and age on dM/dt_acc_ cannot be treated independently. With the aim to identify reliable correlations between mass, age, and dM/dt_acc_, we used a multivariate linear regression fit between these parameters for our PMS candidates. The comparison between our results and those obtained in other SFRs of our Galaxy and the Magellanic Clouds confirms the importance of the metallicity for the study of the dM/dt_acc_ evolution in clusters with different environmental conditions.
- ID:
- ivo://CDS.VizieR/J/AJ/132/781
- Title:
- 2MASS colours of Magellanic cloud star clusters
- Short Name:
- J/AJ/132/781
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The (rest-frame) near-IR domain contains important stellar population diagnostics and is often used to estimate masses of galaxies at low, as well as high, redshifts. However, many stellar population models are still relatively poorly calibrated in this part of the spectrum. To allow an improvement of this calibration we present a new database of integrated nearIR JHKs magnitudes for 75 star clusters in the Magellanic Clouds, using the Two Micron All Sky Survey (2MASS). The majority of the clusters in our sample have robust age and metallicity estimates from color-magnitude diagrams available in the literature, and populate a range of ages from 10Myr to 15Gyr and a range in [Fe/H] from -2.17 to +0.01dex. A comparison with matched star clusters in the 2MASS Extended Source Catalog (XSC) reveals that the XSC only provides a good fit to the unresolved component of the cluster stellar population. We also compare our results with the often-cited single-channel JHK photometry of Persson and coworkers (1983ApJ...266..105P).
- ID:
- ivo://CDS.VizieR/J/AJ/150/95
- Title:
- Masses and ages of YSOs in Per OB2
- Short Name:
- J/AJ/150/95
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have performed a Wide-Field Infrared Survey Explorer based study to identify and characterize young stellar objects (YSOs) in the 12{deg}x12{deg} Perseus OB2 association. A spectral energy distribution (SED) slope in the range of 3.4-12{mu}m and 5{sigma} selection criteria were used to select our initial sample. Further manual inspection reduced our final catalog to 156 known and 119 YSO candidates. The spatial distribution of newly found YSOs all over the field shows an older generation of star formation in which most of its massive members have evolved into main-sequence stars. In contrast, the majority of younger members lie within the Perseus molecular cloud and currently active star-forming clusters such as NGC 1333 and IC 348. We also identified an additional 66 point sources that passed YSO selection criteria but are likely AGB stars. However, their spatial distribution suggests that they may contain a fraction of the YSOs. Comparing our results with the commonly used color-color selections, we found that while the color selection method fails in picking up bright but evolved weak disks, our SED fitting method can identify such sources, including transitional disks. In addition, we have less contamination with background sources such as galaxies, but at a price of losing fainter (J_mag_>12) YSOs. Finally, we employed a Bayesian Monte Carlo SED fitting method to determine the characteristics of each YSO candidate. Distribution of SED slopes and model-driven age and mass confirms separated YSO populations with three suggested age groups of younger than 1Myr old, 1-5Myr old, and older than 5Myr, which agrees with the age of the Per OB2 association and currently star-forming sites within the cloud.
- ID:
- ivo://CDS.VizieR/J/AJ/149/56
- Title:
- Masses and photometry of 304 M31 old star clusters
- Short Name:
- J/AJ/149/56
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper presents CCD multicolor photometry for 304 old star clusters in the nearby spiral galaxy M31, from which the photometry of 55 star clusters is first obtained. The observations were carried out as a part of the Beijing-Arizona-Taiwan-Connecticut Multicolor Sky Survey from 1995 February to 2008 March, using 15 intermediate-band filters covering 3000-10000{AA}. Detailed comparisons show that our photometry is in agreement with previous measurements. Based on the ages and metallicities from Caldwell et al. and the photometric measurements here, we estimated the clusters' masses by comparing their multicolor photometry with stellar population synthesis models. The results show that the sample clusters have masses between ~3x10^4^M_{sun}_ and ~10^7^M_{sun}_ with a peak of ~4x10^5^_M{sun}_. The masses here are in good agreement with those in previous studies. Combined with the masses of young star clusters of M31 from Wang et al., we find that the peak mass of the old clusters is 10 times that of young clusters.
- ID:
- ivo://CDS.VizieR/J/A+A/404/223
- Title:
- 2MASS IR star clusters in the Galaxy
- Short Name:
- J/A+A/404/223
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We carried out a survey of infrared star clusters and stellar groups on the 2MASS J, H and Ks all-sky release Atlas in the Northern and Equatorial Milky Way (350{deg},l<360{deg}, 0{deg}<l<230{deg}). The search in this zone complements that in the Southern Milky Way (Dutra et al., 2003, Cat. <J/A+A/400/533>). The method concentrates efforts on the directions of known optical and radio nebulae. The present study provides 167 new infrared clusters, stellar groups and candidates. Combining the two studies for the whole Milky Way, 346 infrared clusters, stellar groups and candidates were discovered, whereas 315 objects were previously known. They constitute an important new sample for future detailed studies.
- ID:
- ivo://CDS.VizieR/J/AJ/149/26
- Title:
- Massive binary stars from an HST/FGS survey
- Short Name:
- J/AJ/149/26
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of an all-sky survey made with the Fine Guidance Sensor on the Hubble Space Telescope to search for angularly resolved binary systems among massive stars. The sample of 224 stars is comprised mainly of Galactic O- and B-type stars and luminous blue variables, plus a few luminous stars in the Large Magellanic Cloud. The FGS TRANS mode observations are sensitive to the detection of companions with an angular separation between 0.01'' and 1.0'' and brighter than {delta}m=5. The FGS observations resolved 52 binary and 6 triple star systems and detected partially resolved binaries in 7 additional targets (43 of these are new detections). These numbers yield a companion detection frequency of 29% for the FGS survey. We also gathered literature results on the numbers of close spectroscopic binaries and wider astrometric binaries among the sample, and we present estimates of the frequency of multiple systems and the companion frequency for subsets of stars residing in clusters and associations, field stars, and runaway stars. These results confirm the high multiplicity fraction, especially among massive stars in clusters and associations. We show that the period distribution is approximately flat in increments of logP. We identify a number of systems of potential interest for long-term orbital determinations, and we note the importance of some of these companions for the interpretation of the radial velocities and light curves of close binaries that have third companions.
- ID:
- ivo://CDS.VizieR/J/A+A/600/L10
- Title:
- Massive cluster progenitors from ATLASGAL
- Short Name:
- J/A+A/600/L10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The early evolution of massive cluster progenitors is poorly understood. We investigate the fragmentation properties from 0.3pc to 0.06pc scales of a homogenous sample of infrared-quiet massive clumps within 4.5kpc selected from the ATLASGAL survey. Using the ALMA 7m array we detect compact dust continuum emission towards all targets and find that fragmentation, at these scales, is limited. The mass distribution of the fragments uncovers a large fraction of cores above 40M_{sun}_, corresponding to massive dense cores (MDCs) with masses up to ~400M_{sun}_. Seventy-seven percent of the clumps contain at most 3 MDCs per clump, and we also reveal single clumps/MDCs. The most massive cores are formed within the more massive clumps and a high concentration of mass on small scales reveals a high core formation efficiency. The mass of MDCs highly exceeds the local thermal Jeans mass, and we lack the observational evidence of a survey efficiently high level of turbulence or strong enough magnetic fields to keep the most massive MDCs in equilibrium. If already collapsing, the observed fragmentation properties with a high core formation efficiency are consistent with the collapse setting in at parsec scales.
- ID:
- ivo://CDS.VizieR/J/MNRAS/430/676
- Title:
- Massive clusters in the LMC
- Short Name:
- J/MNRAS/430/676
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Large Magellanic Cloud (LMC) is one of the nearest galaxies to us and is one of only few galaxies where the star formation history can be determined from studying resolved stellar populations. We have compiled a new catalogue of ages, luminosities and masses of LMC star clusters and used it to determine the age distribution and dissolution rate of LMC star clusters. We find that the frequency of massive clusters with masses M>5000M_{sun}_ is almost constant between 10 and 200Myr, showing that the influence of residual gas expulsion is limited to the first 10Myr of cluster evolution or clusters less massive than 5000M_{sun}_.
