- ID:
- ivo://CDS.VizieR/J/ApJ/813/25
- Title:
- YSO candidates in W49 observed with Spitzer
- Short Name:
- J/ApJ/813/25
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the initial results of our investigation of the star-forming complex W49, one of the youngest and most luminous massive star-forming regions in our Galaxy. We used Spitzer/Infrared Array Camera (IRAC) data to investigate massive star formation with the primary objective of locating a representative set of protostars and the clusters of young stars that are forming around them. We present our source catalog with the mosaics from the IRAC data. In this study we used a combination of IRAC, MIPS, Two Micron All Sky Survey, and UKIRT Deep Infrared Sky Survey (UKIDSS) data to identify and classify the young stellar objects (YSOs). We identified 232 Class 0/I YSOs, 907 Class II YSOs, and 74 transition disk candidate objects using color-color and color-magnitude diagrams. In addition, to understand the evolution of star formation in W49, we analyzed the distribution of YSOs in the region to identify clusters using a minimal spanning tree method. The fraction of YSOs that belong to clusters with >=7 members is found to be 52% for a cutoff distance of 96", and the ratio of Class II/I objects is 2.1. We compared the W49 region to the G305 and G333 star-forming regions and concluded that W49 has the richest population, with seven subclusters of YSOs.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/818/95
- Title:
- YSO candidates within 5' from the IR bubble N4
- Short Name:
- J/ApJ/818/95
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The physical mechanisms that induce the transformation of a certain mass of gas in new stars are far from being well understood. Infrared bubbles associated with H II regions have been considered to be good samples for investigating triggered star formation. In this paper we report on the investigation of the dust properties of the infrared bubble N4 around the H II region G11.898+0.747, analyzing its interaction with its surroundings and star formation histories therein, with the aim of determining the possibility of star formation triggered by the expansion of the bubble. Using Herschel PACS and SPIRE images with a wide wavelength coverage, we reveal the dust properties over the entire bubble. Meanwhile, we are able to identify six dust clumps surrounding the bubble, with a mean size of 0.50pc, temperature of about 22K, mean column density of 1.7x10^22^/cm2, mean volume density of about 4.4x10^4^/cm3, and a mean mass of 320M_{sun}_. In addition, from PAH emission seen at 8 {mu}m, free-free emission detected at 20cm, and a probability density function in special regions, we could identify clear signatures of the influence of the HII region on the surroundings. There are hints of star formation, though further investigation is required to demonstrate that N4 is the triggering source.
- 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.
- 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.
24145. 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.
- 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).
- 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.
24148. 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).
24150. 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.
