- ID:
- ivo://CDS.VizieR/J/ApJS/234/8
- Title:
- YSO jets from UWISH2. IV. Cygnus-X outflows
- Short Name:
- J/ApJS/234/8
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have performed an unbiased search for outflows from young stars in Cygnus-X using 42deg^2^ of data from the UKIRT Widefield Infrared Survey for H_2_ (UWISH2 Survey), to identify shock-excited near-IR H_2_ emission in the 1-0 S(1) 2.122{mu}m line. We uncovered 572 outflows, of which 465 are new discoveries, increasing the number of known objects by more than 430%. This large and unbiased sample allows us to statistically determine the typical properties of outflows from young stars. We found 261 bipolar outflows, and 16% of these are parsec scale. The typical bipolar outflow is 0.45pc in length and has gaps of 0.025-0.1pc between large knots. The median luminosity in the 1-0 S(1) line is 10^-3^L_{sun}_. The bipolar flows are typically asymmetrical, with the two lobes misaligned by 5{deg}, one lobe 30% shorter than the other, and one lobe twice as bright as the other. Of the remaining outflows, 152 are single- sided and 159 are groups of extended, shock-excited H2 emission without identifiable driving sources. Half of all driving sources have sufficient WISE data to determine their evolutionary status as either protostars (80%) or classical T Tauri stars (20%). One-fifth of the driving sources are variable by more than 0.5mag in the K-band continuum over several years. Several of the newly identified outflows provide excellent targets for follow-up studies. We particularly encourage the study of the outflows and young stars identified in a bright-rimmed cloud near IRAS 20294+4255, which seems to represent a textbook example of triggered star formation.
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Search Results
- 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.
8363. 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.
- 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).
- 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.
- 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.
8367. 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.
- 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
- 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).
- ID:
- ivo://CDS.VizieR/J/A+A/625/A94
- Title:
- YSOs in early-type dwarf galaxies
- Short Name:
- J/A+A/625/A94
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To understand the stellar population content of dwarf early-type galaxies (dEs) and its environmental dependence, we compare the slopes and intrinsic scatter of color-magnitude relations (CMRs) for three nearby clusters, Fornax, Virgo and Coma. Additionally we present and compare internal color profiles of these galaxies to identify central blue regions with younger stars. We use the imaging of the HST/ACS Fornax cluster in the magnitude range of -18:7<=Mg0<=-16:0, to derive magnitudes, colors and color profiles, which we compare with literature measurements from the HST/ACS Virgo and Coma Cluster Survey. We benefit HST accuracy to investigate and parameterize the (g'-z') color profiles of these dEs. Based on analysis of the color profiles, we report a large number of dEs with young stellar populations in their center in all three clusters. While for Virgo and Coma the number of blue-cored dEs is found to be 85%+/-2% and 53%+/-3% respectively, for Fornax, we find that all galaxies have a blue core.We show that bluer cores reside in fainter dEs, similar to the trend seen in nucleated dEs. We find no correlation between the luminosity of the galaxy and the size of its blue core. Moreover, a comparison of the CMRs of the three clusters shows that the scatter in Virgo's CMR is considerably larger than in the Fornax and Coma clusters. Presenting adaptive smoothing we show that the galaxies on the blue side of the CMR often show evidence for dust extinction, which strengthens the interpretation that the bluer colors are due to young stellar populations. We also find that outliers on the red side of the CMR are more compact than expected for their luminosity. We find several of these red outliers in Virgo, often close to more massive galaxies. No red outlying compact early-types are found in Fornax and Coma in this magnitude range while we find three in the Virgo cluster. We show that the CMR of the Fornax and Virgo clusters are slightly bluer than that of Coma. We suggest that the large number of outliers and larger scatter found for the Virgo cluster CMR is a result of Virgos different assembly history.
