331 research outputs found
The low-mass population in the young cluster Stock 8: Stellar properties and Initial Mass Function
The evolution of HII regions/supershells can trigger a new generation of
stars/clusters at their peripheries, with environmental conditions that may
affect the initial mass function, disk evolution and star formation efficiency.
In this paper we study the stellar content and star formation processes in the
young cluster Stock 8, which itself is thought to be formed during the
expansion of a supershell. We present deep optical photometry along with JHK
and 3.6, 4.5 {\mu}m photometry from UKIDSS and Spitzer-IRAC. We use multi-color
criteria to identify the candidate young stellar objects in the region. Using
evolutionary models, we obtain a median log(age) of ~6.5 (~3.0 Myr) with an
observed age spread of ~0.25 dex for the cluster. Monte Carlo simulations of
the population of Stock 8, based on estimates for the photometric uncertainty,
differential reddening, binarity, and variability, indicate that these
uncertainties introduce an age spread of ~0.15 dex. The intrinsic age spread in
the cluster is ~0.2 dex. The fraction of young stellar objects surrounded by
disk is ~35%. The K-band luminosity function of Stock 8 is similar to that of
the Trapezium cluster. The IMF of Stock 8 has a Salpeter- like slope at >0.5
Msun and the IMF flattens and peaks at ~0.4 Msun, below which declines into the
substellar regime. Although Stock 8 is surrounded by several massive stars,
there seems to be no severe environmental effect in the form of IMF due to the
proximity of massive stars around the cluster.Comment: Accepted for publication in Ap
Protoplanetary disks around young stellar and substellar objects in the Orionis cluster
Understanding the evolution and dissipation of protoplanetary disks are
crucial in star and planet formation studies. We report the protoplanetary disk
population in the nearby young Orionis cluster (d408 pc;
age1.8 Myr) and analyse the disk properties such as dependence on stellar
mass and disk evolution. We utilise the comprehensive census of 170
spectroscopic members of the region refined using astrometry from Gaia DR3 for
a wide mass range of 19-0.004 M. Using the near infrared (2MASS)
and mid infrared (WISE) photometry we classify the sources based on the
spectral index into class I, class II, flat spectrum and class III young
stellar objects. The frequency of sources hosting a disk with stellar mass 2
M in this region is 417% which is consistent with the disk
fraction estimated in previous studies. We see that there is no significant
dependence of disk fraction on stellar mass among T Tauri stars (2
M), but we propose rapid disk depletion around higher mass stars (2
M). Furthermore we find the lowest mass of a disk bearing object to be
20 M and the pronounced disk fraction among the brown
dwarf population hints at the formation scenario that brown dwarfs form similar
to low-mass stars.Comment: Accepted for publication in The Journal of Astrophysics and
Astronomy. 17 pages, 6 figures, 2 table
H emission line sources from VLT-MUSE in a low-metallicity star forming region -- Dolidze 25
The process of accretion through circumstellar disks in young stellar objects
is an integral part of star formation and the emission line is a
prominent signature of accretion in low-mass stars. We present the detection
and characterization of emission line sources in the central region
of a distant, low-metallicity young stellar cluster - Dolidze 25 (at 4.5
kpc) - using medium-resolution optical spectra (4750-9350 \r{A} ) obtained with
the Multi-Unit Spectroscopic Explorer (MUSE) at the VLT. We have identified 14
potential accreting sources within a rectangular region of (2 x 1)
towards the center of the cluster based on the detection of strong and broad
emissions in as well as the presence of other emission lines such as
[OI] and . Based on their positions in both photometric color-magnitude
and color-color diagrams, we have also confirmed that these objects belong to
the pre-main sequence phase of star formation. Our results were compared with
the disk and diskless members of the cluster previously identified by Guarcello
et al. (2021) using near-IR colors, and all sources they had identified as
disks were confirmed to be accreting based on the spectroscopic
characteristics
The role of magnetic fields in the fragmentation of the Taurus B213 filament into Sun-type star-forming cores
Fragmentation is a key step in the process of transforming clouds (and their
substructures such as filaments, clumps, and cores) into protostars. The
thermal gas pressure and gravitational collapse are believed to be the primary
agents governing this process, referred to as the thermal Jeans fragmentation.
However, the contributions of other factors (such as magnetic fields and
turbulence) to the fragmentation process remain less explored. In this work, we
have tested possible fragmentation mechanisms by estimating the mean core mass
and mean inter-core separation of the B213 filament. We have used the 14"
resolution James Clerk Maxwell Telescope (JCMT) Submillimetre Common-User
Bolometer Array 2 (SCUBA-2)/POL-2 850 m dust continuum map and combined it
with a Planck 850 m map and Herschel data. We find that in addition to the
thermal contribution, the presence of ordered magnetic fields could be
important in the fragmentation of the B213 filament.Comment: 10 pages, 3 figures, and 5 tables ; Accepted for publication in JOA
Star formation in W3 - AFGL333: Young stellar content, properties and roles of external feedback
One of the key questions in the field of star formation is the role of
stellar feedback on subsequent star formation process. The W3 giant molecular
cloud complex at the western border of the W4 super bubble is thought to be
influenced by the stellar winds of the massive stars in W4. AFGL333 is a ~10^4
Msun cloud within W3. This paper presents a study of the star formation
activity within AFGL333 using deep JHKs photometry obtained from the NOAO
Extremely Wide-Field Infrared Imager combined with Spitzer-IRAC-MIPS
photometry. Based on the infrared excess, we identify 812 candidate young
stellar objects in the complex, of which 99 are classified as Class I and 713
are classified as Class II sources. The stellar density analysis of young
stellar objects reveals three major stellar aggregates within AFGL333, named
here AFGL333-main, AFGL333-NW1 and AFGL333-NW2. The disk fraction within
AFGL333 is estimated to be ~50-60%. We use the extinction map made from the
H-Ks colors of the background stars to understand the cloud structure and to
estimate the cloud mass. The CO-derived extinction map corroborates the cloud
structure and mass estimates from NIR color method. From the stellar mass and
cloud mass associated with AFGL333, we infer that the region is currently
forming stars with an efficiency of ~4.5% and at a rate of ~2 - 3 Msun
Myr-1pc-2. In general, the star formation activity within AFGL333 is comparable
to that of nearby low mass star-forming regions. We do not find any strong
evidence to suggest that the stellar feedback from the massive stars of nearby
W4 super bubble has affected the global star formation properties of the
AFGL333 region.Comment: 17 pages, 9 figures, Accepted for publication in Ap
Membership analysis and 3D kinematics of the star-forming complex around Trumpler 37 using Gaia-DR3
Identifying and characterizing young populations of star-forming regions is
crucial to unravel their properties. In this regard, Gaia-DR3 data and machine
learning tools are very useful for studying large star-forming complexes. In
this work, we analyze the area of one of our Galaxy's
dominant feedback-driven star-forming complexes, i.e., the region around
Trumpler 37. Using the Gaussian mixture and random forest classifier methods,
we identify 1243 high-probable members in the complex, of which are
new members and are complete down to the mass limit of 0.1 0.2~. The spatial distribution of the stars reveals multiple clusters
towards the complex, where the central cluster around the massive star HD
206267 reveals two sub-clusters. Of the 1243 stars, 152 have radial velocity,
with a mean value of . We investigate stars' internal
and relative movement within the central cluster. The kinematic analysis shows
that the cluster's expansion is relatively slow compared to the whole complex.
This slow expansion is possibly due to newly formed young stars within the
cluster. We discuss these results in the context of hierarchical collapse and
feedback-induced collapse mode of star formation in the complex.Comment: 23 pages, 15 figures, accepted for publication in Ap
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