scholarly journals The Sample of Red Supergiants in 12 Low-mass Galaxies of the Local Group

2021 ◽  
Vol 923 (2) ◽  
pp. 232
Author(s):  
Yi Ren ◽  
Biwei Jiang ◽  
Ming Yang ◽  
Tianding Wang ◽  
Tongtian Ren
Keyword(s):  
Near Infrared ◽  
Local Group ◽  
Formation Rate ◽  
Mass Function ◽  
Initial Mass Function ◽  
Distance Modulus ◽  
Dwarf Stars ◽  
Red Supergiants ◽  
Low Mass ◽  
Red Giant

Abstract This work establishes the most complete sample of red supergiants (RSGs) in 12 low-mass galaxies (WLM, IC 10, NGC 147, NGC 185, IC 1613, Leo A, Sextans B, Sextans A, NGC 6822, Pegasus Dwarf, SMC, and LMC) of the Local Group, which forms a solid basis to study the properties of RSGs as well as the star formation rate and initial mass function of the galaxies. After removing the foreground dwarf stars by their obvious branch in the near-infrared color–color diagram ( J − H 0 / H − K 0 ) with the UKIRT/WFCAM and 2MASS photometry as well as the Gaia/EDR3 measurements of proper motion and parallax, RSGs are identified from their location in the color–magnitude diagram J − K 0 / K 0 of the member stars of the specific galaxy. A total of 2190 RSGs are found in 10 dwarf galaxies, and additionally, 4823 and 2138 RSGs are found in LMC and SMC, respectively. The locations of the tip of the red giant branch in the J − K 0 / K 0 diagram are determined to serve as an indicator of the metallicity and distance modulus of the galaxies.

scholarly journals Galactic structure from infrared studies

1979 ◽  
Vol 84 ◽  
pp. 105-111 ◽  
Author(s):  
J. L. Puget ◽  
G. Serra ◽  
C. Ryter
Keyword(s):  
Galactic Center ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Far Infrared ◽  
Mass Function ◽  
Infrared Emission ◽  
Initial Mass Function ◽  
Young Stars ◽  
Infrared Studies ◽  
Red Giant

Star densities on a galactic scale are traced by far infrared emission of dust heated by young stars and by the 2.4 μm radiation of stars in the red giant phase. Coherent results are obtained, pointing to a very strong star formation rate during the last ∼200 My in a ring 5 kpc from the galactic center. A steepening of the initial mass function compared to that observed in the solar vicinity is also suggested.

scholarly journals INFRARED STUDIES OF THE STELLAR CONTENT IN EXTRAGALACTIC SYSTEMS

1981 ◽  
Vol 96 ◽  
pp. 297-316
Author(s):  
Marc Aaronson
Keyword(s):  
Galaxy Formation ◽  
Globular Clusters ◽  
Near Infrared ◽  
Formation Rate ◽  
Absolute Magnitude ◽  
Type Systems ◽  
Morphological Type ◽  
Mass Function ◽  
Initial Mass Function ◽  
Stellar Content

Normal galaxies emit most of their radiation longward of one micron, and many problems related to our understanding of galaxy formation and evolution can be fruitfully addressed with measurements at near-infrared wavelengths. Such problems include the make-up of the red stellar population, the star formation rate, the initial mass function, metallicity effects, and mass-to-light ratio. How these various quantities depend on morphological type, on total mass (or absolute magnitude), on radial position, and on environment is also of great interest. In this review recent infrared observations of extragalactic stars, star clusters, and galaxies having important bearing on these questions are discussed. Particular emphasis is placed on new evidence for the presence of a finite intermediate age population in early-type systems. This evidence comes from observations of intermediate age stars in many Magellanic Cloud globular clusters, observations of such stars in at least one nearby dwarf spheroidal (Fornax), the difficulties of fitting theoretical isochrone models to the red V-K colors of E and SO galaxies, and the differences in the infrared color-magnitude relations for the Virgo and Coma clusters.“It is not very bright to measure a blue magnitude for a red object.”– Vera Rubin

scholarly journals The initial mass function in the extended ultraviolet disc of M83

2019 ◽  
Vol 491 (2) ◽  
pp. 2366-2390 ◽  
Author(s):  
S M Bruzzese ◽  
David A Thilker ◽  
G R Meurer ◽  
Luciana Bianchi ◽  
A B Watts ◽  
...  
Keyword(s):  
Main Sequence ◽  
Hubble Space Telescope ◽  
Formation Rate ◽  
Mass Function ◽  
Initial Mass Function ◽  
High Mass ◽  
Initial Mass ◽  
Main Sequence Stars ◽  
Red Giant ◽  
The Imf

ABSTRACT Using Hubble Space Telescope ACS/WFC data we present the photometry and spatial distribution of resolved stellar populations of four fields within the extended ultraviolet disc (XUV disc) of M83. These observations show a clumpy distribution of main-sequence stars and a mostly smooth distribution of red giant branch stars. We constrain the upper end of the initial mass function (IMF) in the outer disc using the detected population of main-sequence stars and an assumed constant star formation rate (SFR) over the last 300 Myr. By comparing the observed main-sequence luminosity function to simulations, we determine the best-fitting IMF to have a power-law slope α = −2.35 ± 0.3 and an upper mass limit $M_{\rm u}=25_{-3}^{+17} \, \mathrm{M}_\odot$. This IMF is consistent with the observed H $\rm \alpha$ emission, which we use to provide additional constraints on the IMF. We explore the influence of deviations from the constant SFR assumption, finding that our IMF conclusions are robust against all but strong recent variations in SFR, but these are excluded by causality arguments. These results, along with our similar studies of other nearby galaxies, indicate that some XUV discs are deficient in high-mass stars compared to a Kroupa IMF. There are over one hundred galaxies within 5 Mpc, many already observed with HST, thus allowing a more comprehensive investigation of the IMF, and how it varies, using the techniques developed here.

Brown and Black Dwarfs: their Structure, Evolution and Contribution to the Missing Mass

1978 ◽  
Vol 3 (3) ◽  
pp. 227-229 ◽  
Author(s):  
D. J. Stevenson
Keyword(s):  
Galactic Plane ◽  
Mass Density ◽  
Mass Function ◽  
Initial Mass Function ◽  
Structure Evolution ◽  
Low Mass Stars ◽  
Hydrogen Burning ◽  
Missing Mass ◽  
Dwarf Stars ◽  
Low Mass

According to Oort (1965), the mass density in the solar neighbourhood (inferred from the gravity component normal to the galactic plane) is between 50% and 150% greater than the mass density inferred from non-dwarf stars. One possible explanation for the “missing mass” is an overabundance of faint M-dwarfs (Weistrop 1972), but present indications are that this overabundance is either small (Weistrop 1976; Sanduleak 1976) or non-existent (Faber et al. 1976; Eggen 1976). Nevertheless, Salpeter’s initial mass function (Salpeter 1955) suggests that the total mass may be dominated by low mass stars, including masses M≤0.08M⊙ which never undergo significant hydrogen burning.

Low‐Mass Star Formation and the Initial Mass Function in IC 348

1998 ◽  
Vol 508 (1) ◽  
pp. 347-369 ◽  
Author(s):  
K. L. Luhman ◽  
G. H. Rieke ◽  
C. J. Lada ◽  
E. A. Lada
Keyword(s):  
Star Formation ◽  
Mass Function ◽  
Initial Mass Function ◽  
Initial Mass ◽  
Mass Star ◽  
Low Mass

scholarly journals Very Low-Luminosity Objects in Star-Forming Regions

1998 ◽  
Vol 11 (1) ◽  
pp. 423-424
Author(s):  
Motohide Tamura ◽  
Yoichi Itoh ◽  
Yumiko Oasa ◽  
Alan Tokunaga ◽  
Koji Sugitani
Keyword(s):  
Brown Dwarfs ◽  
Mass Function ◽  
T Tauri Stars ◽  
Initial Mass Function ◽  
Formation Mechanisms ◽  
Star Forming ◽  
Star Forming Regions ◽  
T Tauri ◽  
Low Mass ◽  
Stellar Sources

Abstract In order to tackle the problems of low-mass end of the initial mass function (IMF) in star-forming regions and the formation mechanisms of brown dwarfs, we have conducted deep infrared surveys of nearby molecular clouds. We have found a significant population of very low-luminosity sources with IR excesses in the Taurus cloud and the Chamaeleon cloud core regions whose extinction corrected J magnitudes are 3 to 8 mag fainter than those of typical T Tauri stars in the same cloud. Some of them are associated with even fainter companions. Follow-up IR spectroscopy has confirmed for the selected sources that their photospheric temperature is around 2000 to 3000 K. Thus, these very low-luminosity young stellar sources are most likely very low-mass T Tauri stars, and some of them might even be young brown dwarfs.

scholarly journals Processes controlling the initial mass function: interstellar turbulence and magnetic fields

1991 ◽  
Vol 147 ◽  
pp. 407-408
Author(s):  
R. C. Fleck
Keyword(s):  
Magnetic Fields ◽  
Mass Function ◽  
Diffusion Time ◽  
Interstellar Cloud ◽  
Initial Mass Function ◽  
Mass Scaling ◽  
Interstellar Turbulence ◽  
Time Scaling ◽  
Turbulent Pressure ◽  
Low Mass

The observed flattening of the initial stellar mass function at low mass can be accounted for in terms of the different interstellar cloud size-mass scaling and different ambipolar diffusion time scaling for small, thermally-supported clouds and larger clouds supported primarily by turbulent pressure.

scholarly journals Turbulent structure and star formation in a stratified, supernova-driven, interstellar medium

2006 ◽  
Vol 2 (S237) ◽  
pp. 358-362
Author(s):  
M. K. Ryan Joung ◽  
Mordecai-Mark Mac Low
Keyword(s):  
Star Formation ◽  
Interstellar Medium ◽  
Adaptive Mesh Refinement ◽  
Formation Rate ◽  
Three Dimensional ◽  
Adaptive Mesh ◽  
Mass Function ◽  
Initial Mass Function ◽  
Interstellar Turbulence ◽  
Self Gravity

AbstractWe report on a study of interstellar turbulence driven by both correlated and isolated supernova explosions. We use three-dimensional hydrodynamic models of a vertically stratified interstellar medium run with the adaptive mesh refinement code Flash at a maximum resolution of 2 pc, with a grid size of 0.5 × 0.5 × 10 kpc. Cold dense clouds form even in the absence of self-gravity due to the collective action of thermal instability and supersonic turbulence. Studying these clouds, we show that it can be misleading to predict physical properties such as the star formation rate or the stellar initial mass function using numerical simulations that do not include self-gravity of the gas. Even if all the gas in turbulently Jeans unstable regions in our simulation is assumed to collapse and form stars in local freefall times, the resulting total collapse rate is significantly lower than the value consistent with the input supernova rate. The amount of mass available for collapse depends on scale, suggesting a simple translation from the density PDF to the stellar IMF may be questionable. Even though the supernova-driven turbulence does produce compressed clouds, it also opposes global collapse. The net effect of supernova-driven turbulence is to inhibit star formation globally by decreasing the amount of mass unstable to gravitational collapse.

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