- ID:
- ivo://CDS.VizieR/J/other/ARA+A/42.685
- Title:
- Young stars near the Sun
- Short Name:
- J/other/ARA+A/42
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Until the late 1990s the rich Hyades and the sparse UMa clusters were the only coeval, comoving concentrations of stars known within 60 pc of Earth. Both are hundreds of millions of years old. Then beginning in the late 1990s the TW Hydrae Association, the Tucana/Horologium Association, the beta Pictoris Moving Group, and the AB Doradus Moving Group were identified within ~60pc of Earth, and the eta Chamaeleontis cluster was found at 97pc. These young groups (ages 8-50Myr), along with other nearby, young stars, will enable imaging and spectroscopic studies of the origin and early evolution of planetary systems.
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- ID:
- ivo://CDS.VizieR/J/A+A/644/A101
- Title:
- 2403 young stellar groups
- Short Name:
- J/A+A/644/A101
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The purpose of this work is to study the properties of the spatial distribution of the young population in three nearby galaxies in order to better understand the first stages of star formation. We used ACS/HST photometry and the "path-linkage criterion" in order to obtain a catalog of young stellar groups (YSGs) in the galaxy NGC 2403. We studied the internal distribution of stars in these YSGs using the Q parameter. We extended these analyses to the YSGs detected in in NGC 300 and NGC 253 our previous works. We built the young stars' density maps for these three galaxies. Through these maps, we were able to identify and study young stellar structures on larger scales. We found 573 YSGs in the galaxy NGC 2403, for which we derived their individual sizes, densities, luminosity function, and other fundamental characteristics. We find that the vast majority of the YSGs in NGC 2403, NGC 300 and NGC 253 present inner clumpings, following the same hierarchical behavior that we observed in the young stellar structures on larger scales in these galaxies. We derived values of the fractal dimension for these structures between ~1.5 and 1.6. These values are very similar to those obtained in other star forming galaxies and in the interstellar medium, suggesting that the star formation process is regulated by supersonic turbulence.
- ID:
- ivo://CDS.VizieR/J/ApJ/727/64
- Title:
- Young stellar groups and their most massive stars
- Short Name:
- J/ApJ/727/64
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyze the masses and spatial distributions of 14 young stellar groups in Taurus, Lupus3, ChaI, and IC348. These nearby groups, which typically contain 20-40 members, have membership catalogs complete to ~0.02M_{sun}_, and are sufficiently young that their locations should be similar to where they formed. These groups show five properties seen in clusters having many more stars and much greater surface density of stars: (1) a broad range of masses, (2) a concentration of the most massive star toward the center of the group, (3) an association of the most massive star with a high surface density of lower mass stars, (4) a correlation of the mass of the most massive star with the total mass of the group, and (5) the distribution of a large fraction of the mass in a small fraction of the stars.
- ID:
- ivo://CDS.VizieR/J/ApJ/762/88
- Title:
- Young stellar kinematic group candidate members
- Short Name:
- J/ApJ/762/88
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new method based on a Bayesian analysis to identify new members of nearby young kinematic groups. The analysis minimally takes into account the position, proper motion, magnitude, and color of a star, but other observables can be readily added (e.g., radial velocity, distance). We use this method to find new young low-mass stars in the {beta} Pictoris and AB Doradus moving groups and in the TW Hydrae, Tucana-Horologium, Columba, Carina, and Argus associations. Starting from a sample of 758 mid-K to mid-M (K5V-M5V) stars showing youth indicators such as H{alpha} and X-ray emission, our analysis yields 214 new highly probable low-mass members of the kinematic groups analyzed. One is in TW Hydrae, 37 in {beta} Pictoris, 17 in Tucana-Horologium, 20 in Columba, 6 in Carina, 50 in Argus, 32 in AB Doradus, and the remaining 51 candidates are likely young but have an ambiguous membership to more than one association. The false alarm rate for new candidates is estimated to be 5% for {beta} Pictoris and TW Hydrae, 10% for Tucana-Horologium, Columba, Carina, and Argus, and 14% for AB Doradus. Our analysis confirms the membership of 58 stars proposed in the literature. Firm membership confirmation of our new candidates will require measurement of their radial velocity (predicted by our analysis), parallax, and lithium 6708{AA} equivalent width. We have initiated these follow-up observations for a number of candidates, and we have identified two stars (2MASSJ01112542+1526214, 2MASSJ05241914-1601153) as very strong candidate members of the {beta} Pictoris moving group and one strong candidate member (2MASSJ05332558-5117131) of the Tucana-Horologium association; these three stars have radial velocity measurements confirming their membership and lithium detections consistent with young age.
- ID:
- ivo://CDS.VizieR/J/MNRAS/452/3508
- Title:
- Young stellar structures in NGC 6503
- Short Name:
- J/MNRAS/452/3508
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a detailed clustering analysis of the young stellar population across the star-forming ring galaxy NGC 6503, based on the deep Hubble Space Telescope photometry obtained with the Legacy ExtraGalactic UV Survey. We apply a contour-based map analysis technique and identify in the stellar surface density map 244 distinct star-forming structures at various levels of significance. These stellar complexes are found to be organized in a hierarchical fashion with 95 percent being members of three dominant super-structures located along the star-forming ring. The size distribution of the identified structures and the correlation between their radii and numbers of stellar members show power-law behaviours, as expected from scale-free processes. The self-similar distribution of young stars is further quantified from their autocorrelation function, with a fractal dimension of ~1.7 for length-scales between ~20pc and 2.5kpc. The young stellar radial distribution sets the extent of the star-forming ring at radial distances between 1 and 2.5kpc. About 60 percent of the young stars belong to the detected stellar structures, while the remaining stars are distributed among the complexes, still inside the ring of the galaxy. The analysis of the time-dependent clustering of young populations shows a significant change from a more clustered to a more distributed behaviour in a time-scale of ~60Myr. The observed hierarchy in stellar clustering is consistent with star formation being regulated by turbulence across the ring. The rotational velocity difference between the edges of the ring suggests shear as the driving mechanism for this process. Our findings reveal the interesting case of an inner ring forming stars in a hierarchical fashion.
- ID:
- ivo://CDS.VizieR/J/ApJ/619/270
- Title:
- Young super star clusters in the starburst of M82
- Short Name:
- J/ApJ/619/270
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Recent results from the Hubble Space Telescope (HST) have resolved starbursts as collections of compact young stellar clusters. Here we present a photometric catalog of the young stellar clusters in the nuclear starburst of M82, observed with the HST WFPC2 in H{alpha} (F656N) and in four optical broadband filters. We identify 197 young super stellar clusters (SSCs). The compactness and high density of the sources led us to develop specific techniques to measure their sizes. Strong extinction lanes divide the starburst into five different zones. In the catalog we include relative coordinates, radii, fluxes, luminosities, masses, equivalent widths, extinctions, and other parameters. Extinction values have been derived from the broadband images.
- 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/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/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.
