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24751. YSO/MS star models in the central molecular zone
ID:
ivo://CDS.VizieR/J/ApJ/799/53
Title:
YSO/MS star models in the central molecular zone
Short Name:
J/ApJ/799/53
Date:
21 Oct 2021
Publisher:
CDS
Description:
In contrast to most other galaxies, star formation rates in the Milky Way can be estimated directly from young stellar objects (YSOs). In the central molecular zone the star formation rate calculated from the number of YSOs with 24{mu}m emission is up to an order of magnitude higher than the value estimated from methods based on diffuse emission (such as free-free emission). Whether this effect is real or whether it indicates problems with either or both star formation rate measures is not currently known. In this paper, we investigate whether estimates based on YSOs could be heavily contaminated by more evolved objects such as main-sequence stars. We present radiative transfer models of YSOs and of main-sequence stars in a constant ambient medium which show that the main-sequence objects can indeed mimic YSOs at 24{mu}m. However, we show that in some cases the main-sequence models can be marginally resolved at 24{mu}m, whereas the YSO models are always unresolved. Based on the fraction of resolved MIPS 24{mu}m sources in the sample of YSOs previously used to compute the star formation rate, we estimate the fraction of misclassified "YSOs" to be at least 63%, which suggests that the star formation rate previously determined from YSOs is likely to be at least a factor of three too high.
24752. YSO near-infrared properties
ID:
ivo://CDS.VizieR/J/AJ/130/1145
Title:
YSO near-infrared properties
Short Name:
J/AJ/130/1145
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present high-resolution (R~18000), high signal-to-noise ratio, 2{mu}m spectra of 52 IR-selected Class I and flat-spectrum young stellar objects in the Taurus-Auriga, {rho} Ophiuchi, Serpens, Perseus, and Corona Australis dark clouds. We detect key absorption lines in 41 objects and fit synthetic spectra generated from pre-main-sequence models to deduce the effective temperatures, surface gravities, near-IR veilings, rotation velocities, and radial velocities of each of these 41 sources.
24753. YSOs and candidate protostars catalog.
ID:
ivo://CDS.VizieR/J/PASP/107/617
Title:
YSOs and candidate protostars catalog.
Short Name:
J/PASP/107/617
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have compiled a catalog of candidate protostars from the major astronomical journals up to the end of 1993. The Belchman-Ichikawa color criterion was used as the main test of an author's claim that a source should be deemed a candidate protostar. Names, positions (1950 and 2000), LSR velocities, information on whether there are associated outflows, and references are provided. This catalog is meant to update an earlier compilation by Wynn-Williams (1982).
24754. YSOs APEX-CHAMP^+^ high-J CO maps
ID:
ivo://CDS.VizieR/J/A+A/576/A109
Title:
YSOs APEX-CHAMP^+^ high-J CO maps
Short Name:
J/A+A/576/A109
Date:
21 Oct 2021
Publisher:
CDS
Description:
During the embedded stage of star formation, bipolar molecular outflows and UV radiation from the protostar are important feedback processes. Both processes reflect the accretion onto the forming star and affect subsequent collapse or fragmentation of the cloud. Our aim is to quantify the feedback, mechanical and radiative, for a large sample of low-mass sources in a consistent manner. The outflow activity is compared to radiative feedback in the form of UV heating by the accreting protostar to search for correlations and evolutionary trends. Large-scale maps of 26 young stellar objects, which are part of the Herschel WISH key program are obtained using the CHAMP+ instrument on the Atacama Pathfinder EXperiment (^12^CO and ^13^CO 6-5; E_up_~100K), and the HARP-B instrument on the James Clerk Maxwell Telescope (^12^CO and ^13^CO 3-2; E_up_~30K). The maps have high spatial resolution, particularly the CO 6-5 maps taken with a 9" beam, resolving the morphology of the outflows. The maps are used to determine outflow parameters and the results are compared with higher-J CO lines obtained with Herschel. Envelope models are used to quantify the amount of UV-heated gas and its temperature from ^13^CO 6-5 observations. All sources in our sample show outflow activity, with the spatial extent decreasing from the Class 0 to the Class I stage. Consistent with previous studies, the outflow force, F_CO_, is larger for Class 0 sources than for Class I sources, even if their luminosities are comparable. The outflowing gas typically extends to much greater distances than the power-law envelope and therefore influences the surrounding cloud material directly. Comparison of the CO 6-5 results with HIFI H2O and PACS high-J CO lines, both tracing currently shocked gas, shows that the two components are linked, even though the transitions do not probe the same gas. The link does not extend down to CO 3-2. The conclusion is that CO 6-5 depends on the shock characteristics (density and velocity), whereas CO 3-2 is more sensitive to conditions in the surrounding environment (density). The radiative feedback is responsible for increasing the gas temperature by a factor of two, up to 30-50K, on scales of a few thousand AU, particularly along the direction of the outflow. The mass of the UV heated gas exceeds the mass contained in the entrained outflow in the inner ~3000AU and is therefore at least as important on small scales.
24755. YSOs around Cepheus B
ID:
ivo://CDS.VizieR/J/ApJ/699/1454
Title:
YSOs around Cepheus B
Short Name:
J/ApJ/699/1454
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Cepheus B (Cep B) molecular cloud and a portion of the nearby Cep OB3b OB association, one of the most active regions of star formation within 1kpc, have been observed with the Infrared Array Camera detector on board the Spitzer Space Telescope. The goals are to study protoplanetary disk evolution and processes of sequential triggered star formation in the region. Out of ~400 pre-main-sequence (PMS) stars selected with an earlier Chandra X-ray Observatory observation, ~95% are identified with mid-infrared sources and most of these are classified as diskless or disk-bearing stars. The discovery of the additional >200 IR-excess low-mass members gives a combined Chandra+Spitzer PMS sample that is almost complete down to 0.5M_{sun}_ outside of the cloud, and somewhat above 1M_{sun}_ in the cloud.
24756. YSOs candidates and knots in CrA cloud
ID:
ivo://CDS.VizieR/J/ApJS/194/43
Title:
YSOs candidates and knots in CrA cloud
Short Name:
J/ApJS/194/43
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present Spitzer Space Telescope IRAC and MIPS observations of a 0.85deg^2^ field including the Corona Australis (CrA) star-forming region. At a distance of 130pc, CrA is one of the closest regions known to be actively forming stars, particularly within its embedded association, the Coronet. Using the Spitzer data, we identify 51 young stellar objects (YSOs) in CrA which include sources in the well-studied Coronet cluster as well as sources distributed throughout the molecular cloud. Twelve of the YSOs discussed are new candidates, one of which is located in the Coronet. Known YSOs retrieved from the literature are also added to the list, and a total of 116 candidate YSOs in CrA are compiled. A clustering analysis was also performed, finding that the main cluster core, consisting of 68 members, is elongated (having an aspect ratio of 2.36), with a circular radius of 0.59pc and mean surface density of 150pc^-2^. In addition, we analyze outflows and jets in CrA by means of new CO and H2 data. We present 1.3mm interferometric continuum observations made with the Submillimeter Array (SMA) covering R CrA, IRS 5, IRS 7, and IRAS 18595-3712 (IRAS 32).
24757. YSOs detection with W filter
ID:
ivo://CDS.VizieR/J/PASP/132/J4401
Title:
YSOs detection with W filter
Short Name:
J/PASP/132/J4401
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the design and implementation of a medium-band near-IR filter tailored for detecting low-mass stars and brown dwarfs from the summit of Maunakea. The W-band filter is centered at 1.45{mu}m with a bandpass width of 6%, designed to measure the depth of the H_2_O water absorption prominent in objects with spectral types of M6 and later. When combined with standard J and H photometry, the W-band filter is designed to determine spectral types to ~=1.4 subtypes for late-M and L dwarfs, largely independent of surface gravity and reddening. This filter's primary application is completing the census of young substellar objects in star-forming regions, using W-band selection to greatly reduce contamination by reddened background stars that impede broad-band imaging surveys. We deployed the filter on the UH 88 inch telescope to survey ~3 degree^2^ of the NGC 1333, IC 348, and {rho} Ophiuchus star-forming regions. Our spectroscopic followup of W-band selected candidates resulted in the confirmation of 48 ultracool dwarfs with a success rate of 89%, demonstrating the efficacy of this new filter and selection method.
24758. 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.
24759. 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.
24760. 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.

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