- ID:
- ivo://CDS.VizieR/J/MNRAS/431/1005
- Title:
- IC 2391 and Argus young stars
- Short Name:
- J/MNRAS/431/1005
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We explore the possible connection between the open cluster IC 2391 and the unbound Argus association identified by the search for associations containing young stars survey. In addition to common kinematics and ages between these two systems, here we explore their chemical abundance patterns to confirm if the two substructures shared a common origin. We carry out a homogeneous high-resolution elemental abundance study of eight confirmed members of IC 2391 as well as six members of the Argus association using UVES spectra. We derive spectroscopic stellar parameters and abundances for Fe, Na, Mg, Al, Si, Ca, Ti, Cr, Ni and Ba. All stars in the open cluster and Argus association were found to share similar abundances with the scatter well within the uncertainties, where [Fe/H]=-0.04+/-0.03 for cluster stars and [Fe/H]=-0.06+/-0.05 for Argus stars. Effects of overionization/excitation were seen for stars cooler than roughly 5200K as previously noted in the literature. Also, enhanced Ba abundances of around 0.6dex were observed in both systems. The common ages, kinematics and chemical abundances strongly support the fact that the Argus association stars originated from the open cluster IC 2391. Simple modelling of this system finds this dissolution to be consistent with two-body interactions.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/135/823
- Title:
- ICMF of super star clusters
- Short Name:
- J/AJ/135/823
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The initial cluster mass function (ICMF) is a fundamental property of star formation in galaxies. To gauge its universality, we measure and compare the ICMFs in irregular and spiral galaxies. Our sample of irregular galaxies is based on 13 nearby galaxies selected from a volume-limited sample from the fifth data release of the Sloan Digital Sky Survey (SDSS), from which about 320 young (<=20Myr), massive (>~3x10^49M_{sun}_) clusters or associations were selected using an automated source extraction routine. The extinctions, ages, and masses were determined by comparing their u'g'i'z' magnitudes to those generated from starburst models.
- ID:
- ivo://CDS.VizieR/J/ApJ/746/154
- Title:
- Improved kinematic parallaxes for Sco-Cen members
- Short Name:
- J/ApJ/746/154
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an analysis of the ages and star formation history of the F-type stars in the Upper Scorpius (US), Upper Centaurus-Lupus (UCL), and Lower Centaurus-Crux (LCC) subgroups of Scorpius-Centaurus (Sco-Cen), the nearest OB association. Our parent sample is the kinematically selected Hipparcos sample of de Zeeuw et al. (1999, Cat. J/AJ/117/354), restricted to the 138 F-type members. We have obtained classification-resolution optical spectra and have also determined the spectroscopic accretion disk fraction. With Hipparcos and 2MASS photometry, we estimate the reddening and extinction for each star and place the candidate members on a theoretical H-R diagram. For each subgroup we construct empirical isochrones and compare to published evolutionary tracks.
- ID:
- ivo://CDS.VizieR/J/ApJS/172/663
- Title:
- Infrared observations of the Pleiades
- Short Name:
- J/ApJS/172/663
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We make use of new near- and mid-IR photometry of the Pleiades cluster in order to help identify proposed cluster members. We also use the new photometry with previously published photometry to define the single-star main-sequence locus at the age of the Pleiades in a variety of color-magnitude planes. The new near- and mid-IR photometry extend effectively 2 mag deeper than the 2MASS All-Sky Point Source catalog, and hence allow us to select a new set of candidate very low-mass and substellar mass members of the Pleiades in the central square degree of the cluster. We identify 42 new candidate members fainter than K_s_=14 (corresponding to 0.1M_{sun}_). These candidate members should eventually allow a better estimate of the cluster mass function to be made down to of order 0.04M_{sun}_. We also use new IRAC data, in particular the images obtained at 8um, in order to comment briefly on interstellar dust in and near the Pleiades.
- ID:
- ivo://CDS.VizieR/J/ApJ/784/126
- Title:
- Infrared photometry of all known members in Taurus
- Short Name:
- J/ApJ/784/126
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have compiled photometry at 3.4, 4.6, 12, and 22{mu}m from the all-sky survey performed by the Wide-field Infrared Survey Explorer (WISE) for all known members of the Taurus complex of dark clouds. Using these data and photometry from the Spitzer Space Telescope, we have identified members with infrared excess emission from circumstellar disks and have estimated the evolutionary stages of the detected disks, which include 31 new full disks and 16 new candidate transitional, evolved, evolved transitional, and debris disks. We have also used the WISE All-Sky Source Catalog to search for new disk-bearing members of Taurus based on their red infrared colors. Through optical and near-infrared spectroscopy, we have confirmed 26 new members with spectral types of M1-M7. The census of disk-bearing stars in Taurus should now be largely complete for spectral types earlier than ~M8(M{>~}0.03M_{sun}_).
- ID:
- ivo://CDS.VizieR/J/ApJ/647/1180
- Title:
- Infrared photometry of Taurus SFR
- Short Name:
- J/ApJ/647/1180
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a search for new members of the Taurus star-forming region using the Infrared Array Camera (IRAC) aboard the Spitzer Space Telescope. With IRAC images of 29.7deg^2^ of Taurus at 3.6, 4.5, 5.8, and 8.0um, we have identified sources with red mid-infrared colors indicative of disk-bearing objects and have obtained optical and infrared spectra of 23 of these candidate members. Through this work, we have discovered 13 new members of Taurus, two of which have spectral types later than M6 and thus are likely to be brown dwarfs, according to the theoretical evolutionary models of Chabrier & Baraffe (2000ApJ...542..464C). This survey indicates that the previous census of Taurus has a completeness of 80% for members with disks. The new members that we have found do not significantly modify the previously measured distributions of Taurus members as a function of position, mass, and extinction. For instance, we find no evidence for a population of highly reddened brown dwarfs ({LAMBDA}_K_~2) that has been missed by previous optical and near-infrared surveys, which suggests that brown dwarf disks are not significantly more flared than disks around stars. In addition to the new members, we also present IRAC photometry for the 149 previously known members that appear within this survey, which includes 27 objects later than M6.
- ID:
- ivo://CDS.VizieR/J/ApJ/629/288
- Title:
- Infrared sources near AFGL 5142
- Short Name:
- J/ApJ/629/288
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Near-infrared JHK' and H_2_ v=1-0 S(1) imaging observations of the star-forming region AFGL 5142 are presented. A cluster of young stars is confirmed to be embedded in the dense molecular cloud core. Many point sources are newly detected. The cluster's K'-magnitude distribution and [H-K'] color peak have brighter and redder magnitudes than those outside the cluster. Many of the cluster sources exhibit infrared excesses typical of T Tauri stars, Herbig Ae/Be stars, and protostars. The observations also reveal new H_2_ line emission around the cluster, exhibiting several jets, filaments, and a faint elliptical structure. The jets are associated with the CO outflows in the region. The powering sources of the jets, the CO outflows, and the small faint elliptical structure are identified and analyzed individually. The strong H_2_ jets and faint diffuse emission further confirm that the cluster is in an early stage of evolution.
- ID:
- ivo://CDS.VizieR/J/A+A/565/A49
- Title:
- Integrated spectroscopy of 6 LMC clusters
- Short Name:
- J/A+A/565/A49
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To increase the number of studied star clusters (SCs) of the Large Magellanic Cloud (LMC), we present flux-calibrated integrated spectra in the optical range ({lambda}=3700-6800{AA}) for six poorly studied LMC SCs of IVA type. This type corresponds to the age range between 200 and 400Myr. We also aim at creating a new template spectrum representative of this age range at the metallicity level of the LMC. Foreground reddening E(B-V) values and ages are derived by applying the template matching method that consists of comparing the line strengths and continuum distribution of the cluster spectra with those of template cluster spectra with known properties. The equivalent width (EW) of the Balmer lines and the diagnostic diagrams involving the sum of EWs of selected spectral lines were also employed as age indicators. For the first time we provide estimates of the clusters' reddenings and ages. As expected, all the clusters appear to be of nearly the same age, their mean value being (400+/-100)Myr, while the resulting mean E(B-V) values range between 0.00 and 0.10mag. The present cluster sample complements previous ones in an effort to gather a spectral library with several clusters per age bin. By averaging the reddening-corrected integrated spectra, weighted by their signal-to-noise (S/N) ratios, a new high S/N ratio template spectrum of 400Myr has been created.
- ID:
- ivo://CDS.VizieR/J/AJ/140/462
- Title:
- Intermediate-mass star-forming regions
- Short Name:
- J/AJ/140/462
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In an effort to understand the factors that govern the transition from low- to high-mass star formation, for the first time we identify a sample of intermediate-mass star-forming regions (IM SFRs) where stars up to (but not exceeding) ~8M_{sun}_ are being produced. We use IRAS colors and Spitzer Space Telescope mid-IR images, in conjunction with millimeter continuum and ^13^CO maps, to compile a sample of 50 IM SFRs in the inner Galaxy. These are likely to be precursors to Herbig AeBe stars and their associated clusters of low-mass stars.
- ID:
- ivo://CDS.VizieR/J/MNRAS/493/2339
- Title:
- Internal motions in OB-associations
- Short Name:
- J/MNRAS/493/2339
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the motions inside 28 OB-associations with the use of Gaia DR2 proper motions. The average velocity dispersion calculated for 28 OB-associations including more than 20 stars with Gaia DR2 proper motion is sigma_v_=4.5km/s. The median virial and stellar masses of OB-associations are 8.9x10^5^ and 8.1x10^3^M_{sun}_, respectively. The median star-formation efficiency in parent giant molecular clouds appears to be epsilon=1.2%. Gaia DR2 proper motions confirm the expansion in the Per OB1, Car OB1 and Sgr OB1 associations found earlier with Gaia DR1 data. We also detect the expansion in Gem OB1, Ori OB1 and Sco OB1 associations which became possible for the first time now when analyzed with Gaia DR2 proper motions. The analysis of the distribution of OB-stars in the Per OB1 association shows the presence of a shell-like structure with the radius of 40 pc. Probably, the expansion of the Per OB1 association started with the velocity greater than the present-day expansion velocity equal to 5.0+/-1.7km/s.
