- 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.
Number of results to display per page
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.
3685. 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.
3689. 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/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/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.
- 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.
3693. 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.
3694. YSOs in N63 and N180
- ID:
- ivo://CDS.VizieR/J/ApJ/678/200
- Title:
- YSOs in N63 and N180
- Short Name:
- J/ApJ/678/200
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We used Spitzer infrared observations to find the young stars of two HII regions in the Large Magellanic Cloud, N63 and N180. The young stellar object (YSO) candidates were identified in each nebula by means of color-color, color-magnitude diagrams, and the shapes of their spectral energy distributions (SEDs). The most luminous YSOs are found near the ionization fronts within strong 8um emission clumps. Most YSOs, less luminous, are seen in projection inside the HII regions. HST images show several Class I stars that have emerged along the borders of the HII regions; other YSOs are embedded in cometary clouds. The most luminous YSO of N63 is connected to a string of pointlike sources. Its SED can be modeled by a central source of stellar mass M_*_ between 7 and 11M_{sun}_, with a circumstellar disk of outer radius R_d_ of ~55AU, and an envelope of moderate accretion rate, M_env_ of ~2x10^-5^M_{sun}_/yr. N180 is experiencing a phase of star formation more intense than N63, attested by the properties of its most luminous YSO: M_*_ of 25M_{sun}_, R_d_ of ~200AU, and M_env_ of ~1.5x10^-3^M_{sun}_/yr. The modes of triggered star formation in N63 and N180 appear similar to those seen in Galactic HII regions.
- ID:
- ivo://CDS.VizieR/J/MNRAS/468/2325
- Title:
- YSOs in star-forming region associated to V582 Aur
- Short Name:
- J/MNRAS/468/2325
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have studied the environment of the FU Ori type star V582 Aur. Our aim is to explore the star-forming region associated with this young eruptive star. Using slitless spectroscopy, we searched for H{alpha} emission stars within a field of 11.5 arcmin x 11.5 arcmin, centred on V582 Aur. Based on UKIDSS and Spitzer Space Telescope data, we further selected infrared-excess young stellar object candidates. In all, we identified 68 candidate low-mass young stars, 16 of which exhibited H{alpha} emission in the slitless spectroscopic images. The colour-magnitude diagram of the selected objects, based on the IPHAS data, suggests that they are low-mass pre-main-sequence stars associated with the Aur OB 1 association, located at a distance of 1.3kpc from Sun. The bright-rimmed globules in the local environment of V582 Aur probably belong to the dark cloud LDN 1516. Our results suggest that star formation in these globules might have been triggered by the radiation field of a few hot members of Aur OB 1. The bolometric luminosity of V582 Aur, based on archival photometric data and on the adopted distance, is 150-320L_{sun}_.
- ID:
- ivo://CDS.VizieR/J/ApJ/759/48
- Title:
- YSOs in the Galactic HII region Sh2-297
- Short Name:
- J/ApJ/759/48
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a multiwavelength study of the Galactic H II region Sh2-297, located in the Canis Major OB1 complex. Optical spectroscopic observations are used to constrain the spectral type of ionizing star HD 53623 as B0V. The classical nature of this H II region is affirmed by the low values of electron density and emission measure, which are calculated to be 756/cm3 and 9.15x10^5^cm^-6^pc using the radio continuum observations at 610 and 1280MHz, and Very Large Array archival data at 1420MHz. To understand local star formation, we identified the young stellar object (YSO) candidates in a region of area ~7.5'x7.5' centered on Sh2-297 using grism slitless spectroscopy (to identify the H{alpha} emission line stars), and near infrared (NIR) observations. NIR YSO candidates are further classified into various evolutionary stages using color-color and color-magnitude (CM) diagrams, giving 50 red sources (H-K>0.6) and 26 Class II-like sources. The mass and age range of the YSOs are estimated to be ~0.1-2M_{sun}_ and 0.5-2Myr using optical (V/V-I) and NIR (J/J-H) CM diagrams. The mean age of the YSOs is found to be ~1Myr, which is of the order of dynamical age of 1.07Myr of the H II region. Using the estimated range of visual extinction (1.1-25mag) from literature and NIR data for the region, spectral energy distribution models have been implemented for selected YSOs which show masses and ages to be consistent with estimated values. The spatial distribution of YSOs shows an evolutionary sequence, suggesting triggered star formation in the region. The star formation seems to have propagated from the ionizing star toward the cold dark cloud LDN1657A located west of Sh2-297.
- ID:
- ivo://CDS.VizieR/J/A+A/362/199
- Title:
- YSOs in the l=+45 ISOGAL field
- Short Name:
- J/A+A/362/199
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The 7 and 15{mu}m observations of the Galaxy obtained by the ISOGAL program offer an unique possibility to investigate and separate the different populations of stars in the Galactic Plane, in particular to study the population of low flux density YSOs which could not be detected with IRAS.
- ID:
- ivo://CDS.VizieR/J/ApJ/721/357
- Title:
- YSOs in the LMC star-forming region N206
- Short Name:
- J/ApJ/721/357
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present analysis of the energetic star-forming region Henize 206 (N206) located near the southern edge of the Large Magellanic Cloud (LMC) based on photometric data from the Spitzer Surveying the Agents of Galaxy Evolution (SAGE-LMC; IRAC 3.6, 4.5, 5.8, 8.0um and MIPS 24um), Infrared Survey Facility near-infrared survey (J, H, Ks), and the Magellanic Clouds Photometric Survey (MCPS UBVI) covering a wavelength range of 0.36-24um. Young stellar object (YSO) candidates are identified based upon their location in infrared color-magnitude space and classified by the shapes of their spectral energy distributions in comparison with a pre-computed grid of YSO models. We identify 116 YSO candidates: 102 are well characterized by the YSO models, predominately Stage I, and 14 may be multiple sources or young sources with transition disks. Careful examination of the individual sources and their surrounding environment allows us to identify a factor of ~14.5 more YSO candidates than have already been identified. The total mass of these well-fit YSO candidates is ~520M_{sun}_. We calculate a current star formation rate of 0.27x10^-1^M_{sun}_/yr/kpc^2^. The distribution of YSO candidates appears to follow shells of neutral material in the interstellar medium.
- ID:
- ivo://CDS.VizieR/J/ApJ/839/108
- Title:
- YSOs in the star-forming regions W51 & W43
- Short Name:
- J/ApJ/839/108
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of our investigation of the star-forming complexes W51 and W43, two of the brightest in the first Galactic quadrant. In order to determine the young stellar object (YSO) populations in W51 and W43 we used color-magnitude relations based on Spitzer mid-infrared and 2MASS/UKIDSS near- infrared data. We identified 302 Class I YSOs and 1178 Class II/transition disk candidates in W51, and 917 Class I YSOs and 5187 Class II/transition disk candidates in W43. We also identified tens of groups of YSOs in both regions using the Minimal Spanning Tree (MST) method. We found similar cluster densities in both regions, even though Spitzer was not able to probe the densest part of W43. By using the Class II/I ratios, we traced the relative ages within the regions and, based on the morphology of the clusters, we argue that several sites of star formation are independent of one another in terms of their ages and physical conditions. We used spectral energy distribution- fitting to identify the massive YSO (MYSO) candidates since they play a vital role in the star formation process, and then examined them to see if they are related to any massive star formation tracers such as UCH II regions, masers, or dense fragments. We identified 17 MYSO candidates in W51, and 14 in W43, respectively, and found that groups of YSOs hosting MYSO candidates are positionally associated with H II regions in W51, though we do not see any MYSO candidates associated with previously identified massive dense fragments in W43.
- ID:
- ivo://CDS.VizieR/J/ApJ/712/797
- Title:
- YSOs in Vul OB1 association
- Short Name:
- J/ApJ/712/797
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Vulpecula OB association, Vul OB1, is a region of active star formation located in the Galactic plane at 2.3kpc from the Sun. Previous studies suggest that sequential star formation is propagating along this 100pc long molecular complex. In this paper, we use Spitzer MIPSGAL and GLIMPSE data to reconstruct the star formation history of Vul OB1, and search for signatures of past triggering events. We make a census of young stellar objects (YSOs) in Vul OB1 based on IR color and magnitude criteria, and we rely on the properties and nature of these YSOs to trace recent episodes of massive star formation. We find 856 YSO candidates, and show that the evolutionary stage of the YSO population in Vul OB1 is rather homogeneous -ruling out the scenario of propagating star formation. We estimate the current star formation efficiency to be ~8%. We also report the discovery of a dozen pillar-like structures, which are confirmed to be sites of small scale triggered star formation.