Search

Start Over Capability Type Simple Cone Search
17981. YSOs from SED fitting in six HII regions
ID:
ivo://CDS.VizieR/J/AJ/144/173
Title:
YSOs from SED fitting in six HII regions
Short Name:
J/AJ/144/173
Date:
21 Oct 2021
Publisher:
CDS
Description:
We investigated six HII regions with infrared, bright rimmed bubble or cometary morphology, in search of quantitative evidence for triggered star formation, both collect and collapse and radiatively driven implosion (RDI). We identified and classified 458 young stellar objects (YSOs) in and around the HII regions. YSOs were determined by fitting a collection of radiative transfer model spectral energy distributions to infrared photometry for a large sample of point sources. We determined areas where there exist enhanced populations of relatively unevolved YSOs on the bright rims of these regions, suggesting that star formation has been triggered there. We further investigated the physical properties of the regions by using radio continuum emission as a proxy for ionizing flux powering the HII regions, and ^13^CO(1-0) observations to measure masses and gravitational stability of molecular clumps. We used an analytical model of collect and collapse triggered star formation, as well as a simulation of RDI, and thus we compare the observed properties of the molecular gas with those predicted in the triggering scenarios. Notably, those regions in our sample that show evidence of cometary, or "blister", morphology are more likely to show evidence of triggering.
17982. YSOs from WISE in Western Circinus cloud
ID:
ivo://CDS.VizieR/J/ApJ/733/L2
Title:
YSOs from WISE in Western Circinus cloud
Short Name:
J/ApJ/733/L2
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Wide-field Infrared Survey Explorer has uncovered a population of young stellar objects (YSOs) in the Western Circinus molecular cloud. Images show the YSOs to be clustered into two main groups that are coincident with dark filamentary structure in the nebulosity. Analysis of photometry shows numerous Class I and II objects. The locations of several of these objects are found to correspond to known dense cores and CO outflows. Class I objects tend to be concentrated in dense aggregates, and Class II objects more evenly distributed throughout the region.
17983. YSOs in BRC 5, 7 and 39
ID:
ivo://CDS.VizieR/J/MNRAS/443/1614
Title:
YSOs in BRC 5, 7 and 39
Short Name:
J/MNRAS/443/1614
Date:
21 Oct 2021
Publisher:
CDS
Description:
Bright-rimmed clouds (BRCs), illuminated and shaped by nearby OB stars, are potential sites of recent/ongoing star formation. Here we present an optical and infrared photometric study of three BRCs: BRC 5, BRC 7 and BRC 39 to obtain a census of the young stellar population, thereby inferring the star formation scenario, in these regions. In each BRC, the Class I sources are found to be located mostly near the bright rim or inside the cloud, whereas the Class II sources are preferentially outside, with younger sources closer to the rim. This provides strong support to sequential star formation triggered by radiation-driven implosion due to the ultraviolet radiation. Moreover, each BRC contains a small group of young stars being revealed at its head, as the next-generation stars. In particular, the young stars at the heads of BRC 5 and BRC 7 are found to be intermediate-/high-mass stars, which, under proper conditions, may themselves trigger further star birth, thereby propagating star formation out to long distances.
17984. YSOs in California Molecular Cloud
ID:
ivo://CDS.VizieR/J/A+A/606/A100
Title:
YSOs in California Molecular Cloud
Short Name:
J/A+A/606/A100
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present new high resolution and dynamic range dust column density and temperature maps of the California Molecular Cloud derived from a combination of Planck and Herschel dust-emission maps, and 2MASS NIR dust-extinction maps. We used these data to determine the ratio of the 2.2{mu}m extinction coefficient to the 850{mu}m opacity and found the value to be close to that found in similar studies of the Orion B and Perseus clouds but higher than that characterizing the Orion A cloud, indicating that variations in the fundamental optical properties of dust may exist between local clouds. We show that over a wide range of extinction, the column density probability distribution function (pdf) of the cloud can be well described by a simple power law (i.e., PDF_N_{prop.to}A_K_^-n^) with an index (n=4.0+/-0.1) that represents a steeper decline with A_K_ than found (n~=3) in similar studies of the Orion and Perseus clouds. Using only the protostellar population of the cloud and our extinction maps we investigate the Schmidt relation, that is, the relation between the protostellar surface density, {Sigma}_*_, and extinction, A_K_, within the cloud. We show that {Sigma}_*_ is directly proportional to the ratio of the protostellar and cloud pdfs, i.e., PDF_*_(A_K_)/PDF_N_(A_K_). We use the cumulative distribution of protostars to infer the functional forms for both {Sigma}_*_ and PDF_*_. We find that {Sigma}_*_ is best described by two power-law functions. At extinctions A_K_<=2.5mag, {Sigma}_*_{prop.to}A_K_^{beta}^ with {beta}=3.3 while at higher extinctions {beta}=2.5, both values steeper than those (~=2) found in other local giant molecular clouds (GMCs). We find that PDF_*_ is a declining function of extinction also best described by two power-laws whose behavior mirrors that of {Sigma}_*_. Our observations suggest that variations both in the slope of the Schmidt relation and in the sizes of the protostellar populations between GMCs are largely driven by variations in the slope, n, of PDF_N_(A_K_). This confirms earlier studies suggesting that cloud structure plays a major role in setting the global star formation rates in GMCs
17985. YSOs in Camelopardalis
ID:
ivo://CDS.VizieR/J/BaltA/19/1
Title:
YSOs in Camelopardalis
Short Name:
J/BaltA/19/1
Date:
21 Oct 2021
Publisher:
CDS
Description:
Using photometric data of infrared surveys, young stellar object (YSO) status is verified for 141 objects selected in our previous papers in the Cassiopeia and Camelopardalis segment of the Milky Way bounded by Galactic Using photometric data of infrared surveys, young stellar object (YSO) status is verified for 141 objects selected in our previous papers in the Cassiopeia and Camelopardalis segment of the Milky Way bounded by Galactic (l, b) = 132-158{deg}, +/-12{deg}). The area includes the known starforming regions in the emission nebulae W3, W4 and W5 and the massive YSOAFGL 490. Spectral energy distribution (SED) curves between 700 nm and 160um, constructed from the GSC 2, 2MASS, IRAS, MSX, Spitzer and AKARI data, are used to estimate the evolutionary stages of these stars.
17986. YSOs in DROXO (Deep rho Oph XMM obs.)
ID:
ivo://CDS.VizieR/J/A+A/519/A34
Title:
YSOs in DROXO (Deep rho Oph XMM obs.)
Short Name:
J/A+A/519/A34
Date:
21 Oct 2021
Publisher:
CDS
Description:
X-rays from very young stars are powerful probes to investigate the mechanisms at work in the very first stages of the star formation and the origin of X-ray emission in very young stars. We present results from a 500ks long observation of the rho Ophiuchi cloud with a XMM-Newton large program named DROXO, aiming at studying the X-ray emission of deeply embedded young stellar objects (YSOs).
17987. YSOs in Herschel-Hi-GAL survey
ID:
ivo://CDS.VizieR/J/A+A/549/A130
Title:
YSOs in Herschel-Hi-GAL survey
Short Name:
J/A+A/549/A130
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Herschel survey of the Galactic plane (Hi-GAL) provides a unique opportunity to study star formation over large areas of the sky and different environments in the Milky Way. We use the best-studied Hi-GAL fields to date, two 2{deg}x2{deg} tiles centered on (l,b)=(30{deg}, 0{deg}) and (l,b)=(59{deg},0{deg}), to study the star formation activity in these regions of the sky using a large sample of well-selected young stellar objects (YSOs). We used the science demonstration phase Hi-GAL fields, where a tremendous effort has been made to identify the newly formed stars and to derive their properties as accurately as possible, e.g. distance, bolometric luminosity, envelope mass, and stage of evolution. We estimated the star formation rate (SFR) for these fields using the number of candidate YSOs and their average time scale to reach the zero age main sequence, and compared it with the rate estimated using their integrated luminosity at 70um, combined with an extragalactic star formation indicator.
17988. YSOs in LDN 1641 with Hectochelle spectra
ID:
ivo://CDS.VizieR/J/ApJS/207/5
Title:
YSOs in LDN 1641 with Hectochelle spectra
Short Name:
J/ApJS/207/5
Date:
21 Oct 2021
Publisher:
CDS
Description:
We investigate the young stellar objects (YSOs) in the Lynds 1641 (L1641) cloud using multi-wavelength data including Spitzer, WISE, the Two Micron All Sky Survey, and XMM covering ~1390 YSOs across a range of evolutionary stages. In addition, we targeted a sub-sample of YSOs for optical spectroscopy with the MMT/Hectospec and the MMT/Hectochelle. We use these data, along with archival photometric data, to derive spectral types, extinction values, masses, ages, and accretion rates. We obtain a disk fraction of ~50% in L1641. The disk frequency is almost constant as a function of stellar mass with a slight peak at log (M_*_/M_{sun}_){approx}-0.25. The analysis of multi-epoch spectroscopic data indicates that the accretion variability of YSOs cannot explain the two orders of magnitude of scatter for YSOs with similar masses. Forty-six new transition disk (TD) objects are confirmed in this work, and we find that the fraction of accreting TDs is lower than for optically thick disks (40%-45% versus 77%-79%, respectively). We confirm our previous result that the accreting TDs have a median accretion rate similar to normal optically thick disks. We confirm that two star formation modes (isolated versus clustered) exist in L1641. We find that the diskless YSOs are statistically older than the YSOs with optically thick disks and the TD objects have a median age that is intermediate between those of the other two populations. We tentatively study the star formation history in L1641 based on the age distribution and find that star formation started to be active 2-3 Myr ago.
17989. YSOs in 9 LMC star forming regions
ID:
ivo://CDS.VizieR/J/A+A/542/A66
Title:
YSOs in 9 LMC star forming regions
Short Name:
J/A+A/542/A66
Date:
21 Oct 2021
Publisher:
CDS
Description:
We introduce a new set of selection criteria for the identification of infrared bright young stellar object (YSO) candidates and apply them to nine HII regions in the Large Magellanic Cloud (LMC), focusing particularly on lower mass candidates missed by most surveys. Data are from the Spitzer Space Telescope legacy program SAGE (Surveying the Agents of Galaxy Evolution; Meixner et al. 2006, Cat. J/AJ/132/2268, see also II/305), combined with optical photometry from the Magellanic Clouds Photometric Survey (MCPS; Zaritsky et al. 1997AJ....114.1002Z) and near-infrared photometry from the InfraRed Survey Facility (IRSF; Kato et al. 2007, Cat. II/288). We choose regions of diverse physical size, star formation rates (SFRs), and ages. We also cover a wide range of locations and surrounding environments in the LMC. These active star-forming regions are LHA 120-N 11, N 44, N 51, N 105, N 113, N 120, N 144, N 160, and N 206. Some have been well-studied (e.g., N11, N44, N160) in the past, while others (e.g., N51, N144) have received little attention. We identify 1045 YSO candidates, including 918 never before identified and 127 matching previous candidate lists. We characterize the evolutionary stage and physical properties of each candidate using the spectral energy distribution (SED) fitter of Robitaille et al. (2007ApJS..169..328R) and estimate mass functions and SFRs for each region.
17990. YSOs in L1630N and L1641
ID:
ivo://CDS.VizieR/J/A+A/504/461
Title:
YSOs in L1630N and L1641
Short Name:
J/A+A/504/461
Date:
21 Oct 2021
Publisher:
CDS
Description:
Knowledge of the evolution of circumstellar accretion disks is pivotal to our understanding of star and planet formation; and yet despite intensive theoretical and observational studies, the disk dissipation process is not well understood. Infrared observations of large numbers of young stars, as performed by the Spitzer Space Telescope, may advance our knowledge of this inherently complex process. While infrared data reveal the evolutionary status of the disk, they hold little information on the properties of the central star and the accretion characteristics. Existing 2MASS and Spitzer archive data of the Lynds 1630N and 1641 clouds in the Orion GMC provide disk properties of a large number of young stars. We wish to complement these data with optical data that provide the physical stellar parameters and accretion characteristics.

Limit your search

more »

more »

more »

more »

  • 218,078
  • 111

more »

more »