- ID:
- ivo://CDS.VizieR/J/ApJS/176/457
- Title:
- Taurus dark cloud background star catalog
- Short Name:
- J/ApJS/176/457
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Normal field stars located behind dense clouds are a valuable resource in interstellar astrophysics, as they provide continua in which to study phenomena such as gas-phase and solid-state absorption features, interstellar extinction, and polarization. This paper reports the results of a search for highly reddened stars behind the Taurus Dark Cloud complex. We use the Two Micron All Sky Survey (2MASS) Point Source Catalog to survey a ~50deg^2^ area of the cloud to a limiting magnitude of Ks=10.0. Photometry in the 1.2-2.2um passbands from 2MASS is combined with photometry at longer infrared wavelengths (3.6-12um) from the Spitzer Space Telescope and the Infrared Astronomical Satellite to provide effective discrimination between reddened field stars and young stellar objects (YSOs) embedded in the cloud. Our final catalog contains 248 confirmed or probable background field stars, together with estimates of their total visual extinctions, which span the range 2<A_V_<29mag. We also identify the 2MASS source J04292083+2742074 (IRAS 04262+2735) as a previously unrecognized candidate YSO, based on the presence of infrared emission greatly in excess of that predicted for a normal reddened photosphere at wavelengths >5um.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/159/273
- Title:
- Taurus members & nonmembers with K2 data
- Short Name:
- J/AJ/159/273
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an analysis of K2 light curves (LCs) from Campaigns 4 and 13 for members of the young (~3Myr) Taurus association, in addition to an older (~30Myr) population of stars that is largely in the foreground of the Taurus molecular clouds. Out of 156 of the highest-confidence Taurus members, we find that 81% are periodic. Our sample of young foreground stars is biased and incomplete, but nearly all stars (37/38) are periodic. The overall distribution of rotation rates as a function of color (a proxy for mass) is similar to that found in other clusters: the slowest rotators are among the early M spectral types, with faster rotation toward both earlier FGK and later M types. The relationship between period and color/mass exhibited by older clusters such as the Pleiades is already in place by Taurus age. The foreground population has very few stars but is consistent with the USco and Pleiades period distributions. As found in other young clusters, stars with disks rotate on average slower, and few with disks are found rotating faster than ~2days. The overall amplitude of the LCs decreases with age, and higher-mass stars have generally lower amplitudes than lower-mass stars. Stars with disks have on average larger amplitudes than stars without disks, though the physical mechanisms driving the variability and the resulting LC morphologies are also different between these two classes.
- ID:
- ivo://CDS.VizieR/J/ApJS/186/259
- Title:
- Taurus Spitzer survey: new candidate members
- Short Name:
- J/ApJS/186/259
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on the properties of pre-main-sequence objects in the Taurus molecular clouds as observed in seven mid- and far-infrared bands with the Spitzer Space Telescope. There are 215 previously identified members of the Taurus star-forming region in our ~44deg^2^ map; these members exhibit a range of Spitzer colors that we take to define young stars still surrounded by circumstellar dust (noting that ~20% of the bona fide Taurus members exhibit no detectable dust excesses). We looked for new objects in the survey field with similar Spitzer properties, aided by extensive optical, X-ray, and ultraviolet imaging, and found 148 new candidate members of Taurus. We have obtained follow-up spectroscopy for about half the candidate sample, thus far confirming 34 new members, three probable new members, and 10 possible new members, an increase of 15%-20% in Taurus members. Of the objects for which we have spectroscopy, seven are now confirmed extragalactic objects, and one is a background Be star. The remaining 93 candidate objects await additional analysis and/or data to be confirmed or rejected as Taurus members. Most of the new members are Class II M stars and are located along the same cloud filaments as the previously identified Taurus members. Among non-members with Spitzer colors similar to young, dusty stars are evolved Be stars, planetary nebulae, carbon stars, galaxies, and active galactic nuclei.
- ID:
- ivo://CDS.VizieR/J/A+A/599/A14
- Title:
- Taurus ultra-wide pairs
- Short Name:
- J/A+A/599/A14
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This work analyses the spatial distribution of stars in Taurus with a specific focus on multiple stars and wide pairs in order to derive new constraints on star formation and early dynamical evolution scenarios. We collected the multiplicity data of stars in Taurus to build an up-to-date stellar/multiplicity catalog. We first present a general study of nearest-neighbor statistics on spatial random distribution, comparing its analytical distribution and moments to those obtained from Monte Carlo samplings. We introduce the one-point correlation {Psi} function to complement the pair correlation function and define the spatial regimes departing from randomness in Taurus. We then perform a set of statistical studies to characterize the binary regime that prevails in Taurus. The {Psi} function in Taurus has a scale-free trend with a similar exponent as the correlation function at small scale. It extends almost 3 decades up to ~60kAU showing a potential extended wide binary regime. This was hidden in the correlation function due to the clustering pattern blending. Distinguishing two stellar populations, single stars versus multiple systems (separation <=1kAU), within Class II/III stars observed at high angular resolution, we highlight a major spatial neighborhood difference between the two populations using nearest-neighbor statistics. The multiple systems are three times more likely to have a distant companion within 10kAU when compared to single stars. We show that this is due to the presence of most probable physical ultra-wide pairs (UWPs, defined as such from their mutual nearest neighbor property), that are themselves generally composed of multiple systems containing up to five stars altogether. More generally, our work highlights; 1) a new large population of candidate UWPs in Taurus within the range 1-60kAU in Taurus and 2) the major local structural role they play up to 60kAU. There are three different types of UWPs; either composed of two tight and comparatively massive stars (MM), by one single and one multiple (SM), or by two distant low-mass singles (SS) stars. These UWPs are biased towards high multiplicity and higher-stellar-mass components at shorter separations. The multiplicity fraction per ultra-wide pair with separation less than 10kAU may be as high as 83.5+/-19.6%. We suggest that these young pre-main sequence UWPs may be pristine imprints of their spatial configuration at birth resulting from a cascade fragmentation scenario of the natal molecular core. They could be the older counterparts, at least for those separated by less than 10kAU, to the <=0.5Myr prestellar cores/Class 0 multiple objects observed at radio/millimeter wavelengths.
- ID:
- ivo://CDS.VizieR/J/A+A/620/A27
- Title:
- Taurus ultra-wide pairs. II.
- Short Name:
- J/A+A/620/A27
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Multiplicity and clustering of young pre-main sequence stars appear as critical clues to understand and constrain the star formation process. Taurus is the archetypical example of the most quiescent star forming regions that may still retain primeval signatures of star formation. This work identifies local overdense stellar structures as a critical scale between wide pairs and loose groups in Taurus. Using the density-based spatial clustering of applications with noise (dbscan) algorithm, and setting its free parameters based on the one-point correlation function and the k-nearest neighbor statistics, we have extracted reliably overdense structures from the sky-projected spatial distribution of stars. Nearly half of the entire stellar population in Taurus is found to be concentrated in 20 very dense, tiny and prolate regions called NESTs (for Nested Elementary STructures). They are regularly spaced (~2pc) and mainly oriented along the principal gas filaments axes. Each NEST contains between four and 23 stars. Inside NESTs, the surface density of stars may be as high as 2500pc^-2^ and the mean value is 340pc^-2^. Nearly half (11) of these NESTs contain about 75% of the class 0 and I objects. The balance between Class I, II, and, III fraction within the NESTs suggests that they may be ordered as an evolutionary temporal scheme, some of them getting infertile with time, while other still giving birth to young stars. We have inferred that only 20% of stars in Taurus do not belong to any kind of stellar groups (either multiple system, ultra wide pairs or NESTs). The mass-size relation for stellar NESTs is very close to the Bonnor-Ebert expectation. The range in mass is about the same as that of dense molecular cores. The distribution in size is bimodal peaking at 12.5 and 50kAU and the distribution of the number of YSOs in NESTs as a function of size exhibits two regimes. We propose that the NESTs in their two size regimes represent the spatial imprints of stellar distribution at birth as they may have emerged within few millions years from their natal cloud either from a single core or from a chain of cores. We have identified them as the preferred sites of star formation in Taurus. These NESTs are the regions of highest stellar density and intermediate spatial scale structures between ultra-wide pairs and loose groups.
- ID:
- ivo://CDS.VizieR/J/A+A/603/A33
- Title:
- Temperature evolution in massive clumps
- Short Name:
- J/A+A/603/A33
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Observational identification of a solid evolutionary sequence for high-mass star-forming regions is still missing. Spectroscopic observations give the opportunity to test possible schemes and connect the phases identified to physical processes. We aim to use the progressive heating of the gas caused by the feedback of high-mass young stellar objects to prove the statistical validity of the most common schemes used to observationally define an evolutionary sequence for high-mass clumps, and characterise the sensitivity of different tracers to this process. From the spectroscopic follow-ups carried out towards submillimeter continuum (dust) emission-selected massive clumps (the ATLASGAL TOP100 sample) with the IRAM 30m, Mopra, and APEX telescopes between 84GHz and 365GHz, we selected several multiplets of CH_3_N, CH_3_CH, and CH_3_H emission lines to derive and compare the physical properties of the gas in the clumps along the evolutionary sequence, fitting simultaneously the large number of lines that these molecules have in the observed band. Our findings are compared with results obtained from optically thin CO isotopologues, dust, and ammonia from previous studies on the same sample. The chemical properties of each species have a major role on the measured physical properties. Low temperatures are traced by ammonia, methanol, and CO (in the early phases), the warm and dense envelope can be probed with CH_3_N, CH_3_CH, and, in evolved sources where CO is abundant in the gas phase, via its optically thin isotopologues. CH_3_H and CH_3_N are also abundant in the hot cores, and we suggest that their high-excitation transitions are good tools to study the kinematics in the hot gas associated with the inner envelope surrounding the young stellar objects that these clumps are hosting. All tracers show, to different degrees according to their properties, progressive warming with evolution. The relation between gas temperature and the luminosity-to-mass (L/M) ratio is reproduced by a simple toy model of a spherical, internally heated clump.
- ID:
- ivo://CDS.VizieR/J/A+A/595/A94
- Title:
- Temperature structures in Galactic center clouds
- Short Name:
- J/A+A/595/A94
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Central Molecular Zone (CMZ) at the center of our Galaxy is the best template to study star formation processes under extreme conditions, similar to those in high-redshift galaxies. We observed on-the-fly maps of para-H_2_CO transitions at 218GHz and 291GHz with the Atacama Pathfinder Experiment (APEX) telescope towards seven Galactic center clouds. From the temperature-sensitive integrated intensity line ratios of H_2_CO(3_21_-2_20_)/H_2_CO(3_03_-2_02_) and H_2_CO(4_22_-3_21_)/H_2_CO(4_04_-3_03_) in combination with radiative transfer models, we produce gas temperature maps of our targets. Our targets have a complex velocity structure that requires a careful disentanglement of the different components. We produce temperature maps for each of the velocity components and show that the temperatures of the components differ, revealing temperature gradients in the clouds.
- ID:
- ivo://CDS.VizieR/J/BaltA/20/317
- Title:
- TGU 619 stars spectral types and distances
- Short Name:
- J/BaltA/20/317
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Interstellar extinction is investigated in a 1.5 square degree area of the Cepheus Flare in the direction of the dark cloud TGU 619 at l=102.5{deg}, b=+15.5{deg} . The study is based on photometric classification of 658 stars in spectral and luminosity classes down to V=16mag using photometry in the Vilnius seven-color system published in Paper I (2009BaltA..18..161Z, Cat. J/BaltA/18/161). The extinction in the investigated area is very uneven: in the most transparent directions we find an extinction of 0.3-1.1mag while in the darkest directions the maximum extinction observed is 2.6mag. The real extinction should be considerably larger since in the direction of some cloud clumps no stars are seen. The distribution of stars in the AV vs. d plot gives evidence that the dust clouds are located at a distance of 286+/-20pc.
- ID:
- ivo://CDS.VizieR/J/BaltA/18/161
- Title:
- TGU 619 Vilnius photometry
- Short Name:
- J/BaltA/18/161
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The catalog contains magnitudes and color indices of 1304 stars down to ~16.6mag in V measured in the seven-color Vilnius photometric system in the area of 1.5 square degrees with the center at Galactic coordinates 102.4{deg}, +15.5{deg}, containing the dark cloud TGU619 in the Cepheus Flare. For most of the stars spectral and luminosity classes determined from the photometric data are given.
- ID:
- ivo://CDS.VizieR/J/ApJ/786/37
- Title:
- The Auriga-California molecular cloud
- Short Name:
- J/ApJ/786/37
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present observations of the Auriga-California Molecular Cloud (AMC) at 3.6, 4.5, 5.8, 8.0, 24, 70, and 160 {mu}m observed with the IRAC and MIPS detectors as part of the Spitzer Gould Belt Legacy Survey. The total mapped areas are 2.5 deg^2^ with IRAC and 10.47 deg^2^ with MIPS. This giant molecular cloud is one of two in the nearby Gould Belt of star-forming regions, the other being the Orion A Molecular Cloud (OMC). We compare source counts, colors, and magnitudes in our observed region to a subset of the SWIRE data that was processed through our pipeline. Using color-magnitude and color-color diagrams, we find evidence for a substantial population of 166 young stellar objects (YSOs) in the cloud, many of which were previously unknown. Most of this population is concentrated around the LkH{alpha} 101 cluster and the filament extending from it. We present a quantitative description of the degree of clustering and discuss the relative fraction of YSOs in earlier (Class I and F) and later (Class II) classes compared to other clouds. We perform simple SED modeling of the YSOs with disks to compare the mid-IR properties to disks in other clouds and identify 14 classical transition disk candidates. Although the AMC is similar in mass, size, and distance to the OMC, it is forming about 15-20 times fewer stars.
