- ID:
- ivo://CDS.VizieR/J/ApJ/707/1417
- Title:
- HST view of YSOs in the LMC
- Short Name:
- J/ApJ/707/1417
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used archival Hubble Space Telecope (HST) H{alpha} images to study the immediate environments of massive and intermediate-mass young stellar object (YSO) candidates in the Large Magellanic Cloud (LMC). The sample of YSO candidates, taken from Gruendl & Chu (2009, Cat. J/ApJS/184/172), was selected based on Spitzer IRAC and MIPS observations of the entire LMC and complementary ground-based optical and near-infrared observations. We found HST H{alpha} images for 99 YSO candidates in the LMC, of which 82 appear to be genuine YSOs. More than 95% of the YSOs are found to be associated with molecular clouds. YSOs are seen in three different kinds of environments in the H{alpha} images: in dark clouds, inside or on the tip of bright-rimmed dust pillars, and in small HII regions. Comparisons of spectral energy distributions for YSOs in these three different kinds of environments suggest that YSOs in dark clouds are the youngest, YSOs with small HII regions are the most evolved, and YSOs in bright-rimmed dust pillars span a range of intermediate evolutionary stages. This rough evolutionary sequence is substantiated by the presence of silicate absorption features in the Spitzer Infrared Spectrograph spectra of some YSOs in dark clouds and in bright-rimmed dust pillars, but not those of YSOs in small HII regions. We present a discussion on triggered star formation for YSOs in bright-rimmed dust pillars or in dark clouds adjacent to HII regions. As many as 50% of the YSOs are resolved into multiple sources in high-resolution HST images.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/730/78
- Title:
- Hubble and Spitzer photometry of NGC 602
- Short Name:
- J/ApJ/730/78
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the photometric catalogs for the star-forming cluster NGC 602 in the wing of the Small Magellanic Cloud covering a range of wavelengths from optical (HST/ACS F555W, F814W, and SMARTS/ANDICAM V, I) to infrared (Spitzer/IRAC 3.6, 4.5, 5.8, and 8um and MIPS 24um). Combining this with Infrared Survey Facility near-infrared photometry (J, H, Ks), we compare the young main sequence (MS) and pre-main sequence (PMS) populations prominent in the optical with the current young stellar object (YSO) populations revealed by the infrared. We analyze the MS and PMS population with isochrones in color-magnitude diagrams to derive ages and masses. The optical data reveal ~565 PMS candidates, low-mass Stage III YSOs. We characterize ~40 YSOs by fitting their spectral energy distributions to a grid of models (Robitaille et al. 2007ApJS..169..328R) to derive luminosities, masses, and evolutionary phase (Stages I-III). The higher resolution HST images reveal that ~70% of the YSO candidates are either multiples or protoclusters. For YSOs and PMS sources found in common, we find a consistency in the masses derived. We use the YSO mass function to derive a present-day star formation rate of ~0.2-1.0M_{sun}_/yr/kpc^2^, similar to the rate derived from the optical star formation history suggesting a constant star formation rate for this region.
- ID:
- ivo://CDS.VizieR/II/362
- Title:
- i-band variability of YSOs
- Short Name:
- II/362
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an i-band photometric study of over 800 young stellar objects in the OB association Cep OB3b, which samples timescales from 1 minute to ten years. Using structure functions we show that on all timescales (tau) there is a monotonic decrease in variability from Class I to Class II through the transition disc (TD) systems to Class III, i.e. the more evolved systems are less variable. The Class Is show an approximately power-law increase (tau^0.8^) in variability from timescales of a few minutes to ten years. The Class II, TDs and Class III systems show a qualitatively different behaviour with most showing a power-law increase in variability to a timescale corresponding to the rotational period of the star, with little additional variability beyond that timescale. However, about a third of the Class IIs show lower overall variability, but their variability is still increasing at 10 years. This behaviour can be explained if all Class IIs have two primary components to their variability. The first is an underlying roughly power-law variability spectrum, which evidence from the infrared suggests is driven by accretion rate changes. The second component is an approximately sinusoidal and results from the rotation of the star. We suggest that the systems with dominant longer-timescale variability have a smaller rotational modulation either because they are seen at low inclinations or have more complex magnetic field geometries. We derive a new way of calculating structure functions for large simulated datasets (the "fast structure function"), based on fast Fourier transforms.
- ID:
- ivo://CDS.VizieR/J/MNRAS/431/1005
- Title:
- IC 2391 and Argus young stars
- Short Name:
- J/MNRAS/431/1005
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We explore the possible connection between the open cluster IC 2391 and the unbound Argus association identified by the search for associations containing young stars survey. In addition to common kinematics and ages between these two systems, here we explore their chemical abundance patterns to confirm if the two substructures shared a common origin. We carry out a homogeneous high-resolution elemental abundance study of eight confirmed members of IC 2391 as well as six members of the Argus association using UVES spectra. We derive spectroscopic stellar parameters and abundances for Fe, Na, Mg, Al, Si, Ca, Ti, Cr, Ni and Ba. All stars in the open cluster and Argus association were found to share similar abundances with the scatter well within the uncertainties, where [Fe/H]=-0.04+/-0.03 for cluster stars and [Fe/H]=-0.06+/-0.05 for Argus stars. Effects of overionization/excitation were seen for stars cooler than roughly 5200K as previously noted in the literature. Also, enhanced Ba abundances of around 0.6dex were observed in both systems. The common ages, kinematics and chemical abundances strongly support the fact that the Argus association stars originated from the open cluster IC 2391. Simple modelling of this system finds this dissolution to be consistent with two-body interactions.
165. IC1805 YSOs
- ID:
- ivo://CDS.VizieR/J/MNRAS/468/2684
- Title:
- IC1805 YSOs
- Short Name:
- J/MNRAS/468/2684
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- W4 is a giant HII region ionized by the OB stars of the cluster IC 1805. The HII region/cluster complex has been a subject of numerous investigations as it is an excellent laboratory for studying the feedback effect of massive stars on the surrounding region. However, the low-mass stellar content of the cluster IC 1805 remains poorly studied till now. With the aim to unravel the low-mass stellar population of the cluster, we present the results of a multiwavelength study based on deep optical data obtained with the Canada-France-Hawaii Telescope, infrared data from Two Micron All Sky Survey and SpitzerSpace Telescope and X-ray data from ChandraSpace Telescope. The present optical data set is complete enough to detect stars down to 0.2M_{sun}_, which is the deepest optical observation so far for the cluster. We identified 384 candidate young stellar objects (YSOs; 101 Class I/II and 283 Class III) within the cluster using various colour-colour and colour-magnitude diagrams. We inferred the mean age of the identified YSOs to be ~2.5Myr and mass in the range 0.3-2.5M_{sun}_. The mass function of our YSO sample has a power-law index of -1.23+/-0.23, close to the Salpeter value (-1.35), and consistent with those of other star-forming complexes. We explored the disc evolution of the cluster members and found that the disc-less sources are relatively older compared to the disc bearing YSO candidates. We examined the effect of high-mass stars on the circumstellar discs and within uncertainties, the influence of massive stars on the disc fraction seems to be insignificant. We also studied the spatial correlation of the YSOs with the distribution of gas and dust of the complex to conclude that IC 1805 would have formed in a large filamentary cloud.
- ID:
- ivo://CDS.VizieR/J/A+A/419/999
- Title:
- Infrared knots along protostellar jets
- Short Name:
- J/A+A/419/999
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the near infrared spectra (0.9-2.5 micron) of protostellar jets (HH 24-26, HH72, BHR71). The observations were carried out with Sofi at R~600 with the 1x290arcsec slit. The spectra are dominated by H2 rovibrational lines (v up 5). Faint emission from ionized material in form of [FeII] and [SII] lines is also recognizable. The tables contain the observed lines together with the measured flux. The reported error derives from the rms of the baseline, multiplied by the width of the instrumental profile (30 Angstrom).
- ID:
- ivo://CDS.VizieR/J/A+A/489/1409
- Title:
- Infrared photometry and spectroscopy in L1641N
- Short Name:
- J/A+A/489/1409
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Space-based photometry of sources in our L1641N catalogue, with Spitzer (3.6, 4.5, 5.8, and 8.0 microns) and ISO satellite (6.7 and 14.3 microns), and ground-based photometry with 2.56m Nordic Optical Telescope (NOT) in JHks. Optical spectra (5780-8340{AA}) of Young Stellar Object (YSO) candidates in our L1641N source catalogue. The spectra were taken with the 2.56m Nordic Optical Telescope (NOT) Dec 02-04 2003 and Jan 08-10 2005 (added from both epochs). Each spectrum is contained in a 2052x2 FITS file. The first row in each file is the wavelength [{AA}]. The second row in each file is the flux [erg/s/cm^2^/{AA}]
- ID:
- ivo://CDS.VizieR/J/AJ/148/11
- Title:
- Infrared photometry in Cygnus-X
- Short Name:
- J/AJ/148/11
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Cygnus-X star-forming complex is one of the most active regions of low- and high-mass star formation within 2kpc of the Sun. Using mid-infrared photometry from the IRAC and MIPS Spitzer Cygnus-X Legacy Survey, we have identified over 1800 protostar candidates. We compare the protostellar luminosity functions of two regions within Cygnus-X: CygX-South and CygX-North. These two clouds show distinctly different morphologies suggestive of dissimilar star-forming environments. We find the luminosity functions of these two regions are statistically different. Furthermore, we compare the luminosity functions of protostars found in regions of high and low stellar density within Cygnus-X and find that the luminosity function in regions of high stellar density is biased to higher luminosities. In total, these observations provide further evidence that the luminosities of protostars depend on their natal environment. We discuss the implications this dependence has for the star formation process.
- ID:
- ivo://CDS.VizieR/J/AJ/137/4072
- Title:
- Infrared photometry of G216-2.5 YSOs
- Short Name:
- J/AJ/137/4072
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The giant molecular cloud G216-2.5, also known as Maddalena's cloud or the Maddalena-Thaddeus cloud, is distinguished by an unusual combination of high gas mass (1-6x10^5^_M{sun}), low kinetic temperatures (10K), and the lack of bright far-IR emission. Although star formation has been detected in neighboring satellite clouds, little evidence for star formation has been found in the main body of this cloud. Using a combination of mid-IR observations with the IRAC and Multiband Imaging Photometer for Spitzer instruments onboard the Spitzer Space Telescope, and near-IR images taken with the Flamingos camera on the KPNO 2.1m telescope, we identify a population of 41 young stars with disks and 33 protostars in the center of the cloud. Most of the young stellar objects are coincident with a filamentary structure of dense gas detected in CS (2->1). These observations show that the main body of G216 is actively forming stars, although at a low stellar density comparable to that found in the Taurus cloud.
- ID:
- ivo://CDS.VizieR/J/AJ/150/191
- Title:
- Infrared photometry of YSOs in Cygnus-X DR15
- Short Name:
- J/AJ/150/191
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a multi-wavelength study of the young stellar population in the Cygnus-X DR15 region. We studied young stars that were forming or recently formed at and around the tip of a prominent molecular pillar and an infrared dark cloud. Using a combination of ground-based near-infrared, space-based infrared, and X-ray data, we constructed a point source catalog from which we identified 226 young stellar sources, which we classified into evolutionary classes. We studied their spatial distributions across the molecular gas structures and identified several groups that possibly belong to distinct young star clusters. We obtained samples of these groups and constructed K-band luminosity functions that we compared with those of artificial clusters, allowing us to make first order estimates of the mean ages and age spreads of the groups. We used a ^13^CO(1-0) map to investigate the gas kinematics at the prominent gaseous envelope of the central cluster in DR15, and we inferred that the removal of this envelope is relatively slow compared to other cluster regions, in which the gas dispersal timescale could be similar or shorter than the circumstellar disk dissipation timescale. The presence of other groups with slightly older ages, associated with much less prominent gaseous structures, may imply that the evolution of young clusters in this part of the complex proceeds in periods that last 3-5Myr, perhaps after a slow dissipation of their dense molecular cloud birthplaces.
