scholarly journals A census of massive stars in NGC 346

2019 ◽  
Vol 626 ◽  
pp. A50 ◽  
Author(s):  
P. L. Dufton ◽  
C. J. Evans ◽  
I. Hunter ◽  
D. J. Lennon ◽  
F. R. N. Schneider
Keyword(s):  
Massive Stars ◽  
Rotational Velocity ◽  
Magellanic Cloud ◽  
Small Magellanic Cloud ◽  
Spectral Multiplicity ◽  
Transform Method ◽  
Galactic Clusters ◽  
Early Type Stars ◽  
Stellar Masses ◽  
Inner Region

Spectroscopy for 247 stars towards the young cluster NGC 346 in the Small Magellanic Cloud has been combined with that for 116 targets from the VLT-FLAMES Survey of Massive Stars. Spectral classification yields a sample of 47 O-type and 287 B-type spectra, while radial-velocity variations and/or spectral multiplicity have been used to identify 45 candidate single-lined (SB1) systems, 17 double-lined (SB2) systems, and one triple-lined (SB3) system. Atmospheric parameters (Teff and log g) and projected rotational velocities (ve sin i) have been estimated using TLUSTY model atmospheres; independent estimates of ve sin i were also obtained using a Fourier Transform method. Luminosities have been inferred from stellar apparent magnitudes and used in conjunction with the Teff and ve sin i estimates to constrain stellar masses and ages using the BONNSAI package. We find that targets towards the inner region of NGC 346 have higher median masses and projected rotational velocities, together with smaller median ages than the rest of the sample. There appears to be a population of very young targets with ages of less than 2 Myr, which have presumably all formed within the cluster. The more massive targets are found to have lower projected rotational velocities consistent with previous studies. No significant evidence is found for differences with metallicity in the stellar rotational velocities of early-type stars, although the targets in the Small Magellanic Cloud may rotate faster than those in young Galactic clusters. The rotational velocity distribution for single non-supergiant B-type stars is inferred and implies that a significant number have low rotational velocity (≃10% with ve <  40 km s−1), together with a peak in the probability distribution at ve≃ 300 km s−1. Larger projected rotational velocity estimates have been found for our Be-type sample and imply that most have rotational velocities between 200–450 km s−1.

scholarly journals Seven young star clusters in the inner region of the Small Magellanic Cloud

2008 ◽  
Vol 389 (1) ◽  
pp. 429-440 ◽  
Author(s):  
Andrés E. Piatti ◽  
Doug Geisler ◽  
Ata Sarajedini ◽  
Carme Gallart ◽  
Marina Wischnjewsky
Keyword(s):  
Star Clusters ◽  
Young Star ◽  
Magellanic Cloud ◽  
Small Magellanic Cloud ◽  
Inner Region ◽  
Young Star Clusters

scholarly journals SPITZERSAGE-SMC INFRARED PHOTOMETRY OF MASSIVE STARS IN THE SMALL MAGELLANIC CLOUD

2010 ◽  
Vol 140 (2) ◽  
pp. 416-429 ◽  
Author(s):  
A. Z. Bonanos ◽  
D. J. Lennon ◽  
F. Köhlinger ◽  
J. Th. van Loon ◽  
D. L. Massa ◽  
...  
Keyword(s):  
Massive Stars ◽  
Magellanic Cloud ◽  
Small Magellanic Cloud ◽  
Infrared Photometry

scholarly journals Variability of massive stars with known spectral types in the Small Magellanic Cloud using 8 years of OGLE-III data

2014 ◽  
Vol 562 ◽  
pp. A125 ◽  
Author(s):  
M. Kourniotis ◽  
A. Z. Bonanos ◽  
I. Soszyński ◽  
R. Poleski ◽  
G. Krikelis ◽  
...  
Keyword(s):  
Massive Stars ◽  
Magellanic Cloud ◽  
Small Magellanic Cloud

scholarly journals Massive Star Formation in the Sparsest Environments

2015 ◽  
Vol 11 (S315) ◽  
Author(s):  
Sally Oey ◽  
Joel B. Lamb
Keyword(s):  
Star Formation ◽  
Massive Star ◽  
Massive Stars ◽  
Hii Regions ◽  
Magellanic Cloud ◽  
Small Magellanic Cloud ◽  
Massive Star Formation ◽  
Ob Stars ◽  
Runaway Stars

AbstractThere is growing evidence that massive stars sometimes form in extremely sparse environments. The RIOTS4 survey presents a variety of evidence supporting this scenario, including a sample of 14 OB stars in the Small Magellanic Cloud (SMC) that appear to have formed in situ as field stars. This is based on the presence of dense, symmetric HII regions hosting apparent non-runaway stars. We also present a spatially complete IMF of SMC field OB stars for masses > 7 M⊙, showing that the slope is much steeper than the Salpeter value. The binary fraction among field OB stars is also the same as in clusters, based on a RIOTS4 subsample. These results suggest a relative, but incomplete, suppression of massive star formation in the sparsest regimes.

scholarly journals Mass-loss predictions and stellar masses of early-type stars

2003 ◽  
Vol 212 ◽  
pp. 164-165 ◽  
Author(s):  
Alex de Koter ◽  
Jorick S. Vink
Keyword(s):  
Mass Loss ◽  
Massive Stars ◽  
Spectroscopic Binaries ◽  
Evolution Theory ◽  
Early Type ◽  
Direct Measurements ◽  
Wind Theory ◽  
Early Type Stars ◽  
Stellar Masses

We show that the stellar masses implied by our predictions of the wind properties of massive stars are in agreement with masses derived from evolution theory and from direct measurements using spectroscopic binaries, contrary to previous attempts to derive masses from wind theory.

scholarly journals Origin of Structural and Kinematic Properties of the Small Magellanic Cloud

2009 ◽  
Vol 26 (1) ◽  
pp. 37-57 ◽  
Author(s):  
Kenji Bekki ◽  
Masashi Chiba
Keyword(s):  
Spatial Distribution ◽  
Rotational Velocity ◽  
Magellanic Cloud ◽  
Slow Rotation ◽  
Small Magellanic Cloud ◽  
Disk Model ◽  
Radial Profiles ◽  
Galaxy Interaction ◽  
Spheroidal Model ◽  
Kinematic Properties

AbstractWe investigate structural, kinematic and chemical properties of stars and gas in the Small Magellanic Cloud (SMC) interacting with the Large Magellanic Cloud (LMC) and the Galaxy based on a series of self-consistent chemodynamical simulations. We adopt a new ‘dwarf spheroidal model’ in which the SMC initially has both old stars with a spherical spatial distribution and an extended Hi gas disk. We mainly investigate the evolution of the SMC for the last ∼3 Gyr, during which the Magellanic Stream (MS) and the Magellanic Bridge (MB) could have formed as a result of the LMC–SMC–Galaxy interaction. Our principal results, which can be tested against observations, are as follows: The final spatial distribution of the old stars projected onto the sky is spherical, even after strong LMC–SMC–Galaxy interaction, whereas that of the new ones is significantly flattened and appears to form a bar structure. Old stars have a line-of-sight velocity dispersion σ ≃ 30 km s−1 and slow rotation, with a maximum rotational velocity, V < 20 km s−1 and show asymmetry in the radial profiles. New stars have a smaller Σ than old ones and a significant amount of rotation (V/σ > 1). Hi gas shows velocity dispersions of σ = 10–40 km s−1, a high maximum rotational velocity (V ∼ 50 km s−1) and a spatial distribution similar to that of new stars. New stars with ages younger than 3 Gyr show a negative metallicity gradient in the sense that more metal-rich stars are located in the inner regions of the SMC. The MB inevitably contains old stars with surface mass densities of 6−300 × 104 M⊙ deg−2 depending on initial stellar distributions of the modeled SMC. We find that the dwarf spheroidal model can explain more self-consistently the observed kinematic properties of stars and gas, compared with another type of the model (‘the disk model’) in which the SMC initially consists of stellar and gas disks. We suggest that, to better understand its evolution, the SMC needs to be modeled as having a spheroidal component, rather than being a pure disk.

scholarly journals The Relation Between Field Massive Stars and Clusters

2007 ◽  
Vol 3 (S246) ◽  
pp. 65-66
Author(s):  
M. S. Oey ◽  
N. L. King ◽  
J. Wm. Parker ◽  
J. B. Lamb
Keyword(s):  
Small Groups ◽  
Stellar Population ◽  
Massive Stars ◽  
Magellanic Cloud ◽  
Small Magellanic Cloud ◽  
Multiple Origins ◽  
External Galaxies ◽  
Runaway Stars ◽  
Massive Field

AbstractMassive “field” stars are those that appear in apparent isolation, in contrast to those in clusters. Whereas cluster stars are formed together in large aggregates, simultaneously, field stars have multiple origins. Some massive field stars may be the “tip of the iceberg” on small groups of physically associated stars, while others appear to be “runaway” stars that are dynamically ejected from clusters. What is the intrinsic relation between clusters and field stars, and what is the faction of runaway stars? Since massive stars are the most luminous stellar population, their demographics are accessible in the nearest external galaxies. We present our current efforts to understand these issues for the Small Magellanic Cloud.

scholarly journals A dearth of young and bright massive stars in the Small Magellanic Cloud

2020 ◽  
Author(s):  
A. Schootemeijer ◽  
N. Langer ◽  
D. Lennon ◽  
C. J. Evans ◽  
P. A. Crowther ◽  
...  
Keyword(s):  
Massive Stars ◽  
Magellanic Cloud ◽  
Small Magellanic Cloud

scholarly journals The abundance of satellites around Milky Way- and M31-like galaxies with the TNG50 simulation: a matter of diversity

2021 ◽  
Vol 507 (3) ◽  
pp. 4211-4240 ◽  
Author(s):  
Christoph Engler ◽  
Annalisa Pillepich ◽  
Anna Pasquali ◽  
Dylan Nelson ◽  
Vicente Rodriguez-Gomez ◽  
...  
Keyword(s):  
Milky Way ◽  
Satellite System ◽  
Stellar Mass ◽  
Magellanic Cloud ◽  
High Mass ◽  
Small Magellanic Cloud ◽  
Host Galaxies ◽  
Individual Host ◽  
Stellar Masses ◽  
K Band

ABSTRACT We study the abundance of satellite galaxies around 198 Milky Way- (MW) and M31-like hosts in TNG50, the final installment in the IllustrisTNG suite of cosmological magnetohydrodynamical simulations. MW/M31-like analogues are defined as discy galaxies with stellar masses of $M_* = 10^{10.5 - 11.2}~\rm {M}_\odot$ in relative isolation at z = 0. By defining satellites as galaxies with $M_* \ge 5\times 10^{6}~\rm {M}_\odot$ within $300~\rm {kpc}$ (3D) of their host, we find a remarkable level of diversity and host-to-host scatter across individual host galaxies. The median TNG50 MW/M31-like galaxy hosts a total of $5^{+6}_{-3}$ satellites with $M_* \ge 8 \times 10^6~\rm {M}_\odot$, reaching up to $M_* \sim 10^{8.5^{+0.9}_{-1.1}}~\rm {M}_\odot$. Even at a fixed host halo mass of $10^{12}~\rm {M}_\odot$, the total number of satellites ranges between 0 and 11. The abundance of subhaloes with $M_\rm {dyn} \ge 5 \times 10^7~\rm {M}_\odot$ is larger by a factor of more than 10. The number of all satellites (subhaloes) ever accreted is larger by a factor of 4–5 (3–5) than those surviving to z = 0. Hosts with larger galaxy stellar mass, brighter K-band luminosity, more recent halo assembly, and – most significantly – larger total halo mass typically have a larger number of surviving satellites. The satellite abundances around TNG50 MW/M31-like galaxies are consistent with those of mass-matched hosts from observational surveys (e.g. SAGA) and previous simulations (e.g. Latte). While the observed MW satellite system falls within the TNG50 scatter across all stellar masses considered, M31 is slightly more satellite-rich than our 1σ scatter but well consistent with the high-mass end of the TNG50 sample. We find a handful of systems with both a Large and a Small Magellanic Cloud-like satellite. There is no missing satellites problem according to TNG50.

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