scholarly journals Mild radial variations of the stellar IMF in the bulge of M31.

2021 ◽  
Author(s):  
F La Barbera ◽  
A Vazdekis ◽  
I Ferreras ◽  
A Pasquali
Keyword(s):  
Near Infrared ◽  
Milky Way ◽  
Chemical Species ◽  
Radial Distance ◽  
Major Axis ◽  
Abundance Ratio ◽  
Galactocentric Distance ◽  
Low Mass Stars ◽  
Radial Gradient ◽  
Low Mass

Abstract Using new, homogeneous, long-slit spectroscopy in the wavelength range from ∼0.35 to $\sim 1 \, \mu$m, we study radial gradients of optical and near-infrared (NIR) IMF-sensitive features along the major axis of the bulge of M31, out to a galactocentric distance of ∼200 arcsec (∼800 pc). Based on state-of-the-art stellar population synthesis models with varying Na abundance ratio, we fit a number of spectral indices, from different chemical species (including TiO’s, Ca, and Na indices), to constrain the low-mass (≲ 0.5 M⊙) end slope (i.e. the fraction of low-mass stars) of the stellar IMF, as a function of galactocentric distance. Outside a radial distance of ∼10”, we infer an IMF similar to a Milky-Way-like distribution, while at small galactocentric distances, an IMF radial gradient is detected, with a mildly bottom-heavy IMF in the few inner arcsec. We are able to fit Na features (both NaD and $\rm NaI8190$), without requiring extremely high Na abundance ratios. $\rm [Na/Fe]$ is ∼0.4 dex for most of the bulge, rising up to ∼0.6 dex in the innermost radial bins. Our results imply an overall, luminosity-weighted, IMF and mass-to-light ratio for the M31 bulge, consistent with those for a Milky-Way-like distribution, in contrast to results obtained, in general, for most massive early-type galaxies.

scholarly journals Structure and dynamics of the Milky Way disk as revealed from the radial velocity distributions of APOGEE red clump stars

2016 ◽  
Vol 11 (S321) ◽  
pp. 50-50
Author(s):  
Daisuke Toyouchi ◽  
Masashi Chiba
Keyword(s):  
Near Infrared ◽  
Milky Way ◽  
Radial Velocities ◽  
Galactocentric Distance ◽  
Chemical Abundances ◽  
Structure And Dynamics ◽  
Evolution Experiment ◽  
Dynamical Properties ◽  
Red Clump ◽  
Independent Work

AbstractWe investigate the structure and dynamics of the Milky Way (MW) disk stars based on the analysis of the Apache Point Observatory Galactic Evolution Experiment (APOGEE) data, to infer the past evolution histories of the MW disk component(s) possibly affected by radial migration and/or satellite accretions. APOGEE is the first near-infrared spectroscopic survey for a large number of the MW disk stars, providing their radial velocities and chemical abundances without significant dust extinction effects. We here adopt red-clump (RC) stars (Bovy et al. 2014), for which the distances from the Sun are determined precisely, and analyze their radial velocities and chemical abundances in the MW disk regions covering from the Galactocentric distance, R, of 5 kpc to 14 kpc. We investigate their dynamical properties, such as mean rotational velocities, 〈Vφ〉 and velocity dispersions, as a function of R, based on the MCMC Bayesian method. We find that at all radii, the dynamics of alpha-poor stars, which are candidates of young disk stars, is much different from that of alpha-rich stars, which are candidates of old disk stars. We find that our Jeans analysis for our sample stars reveals characteristic spatial and dynamical properties of the MW disk, which are generally in agreement with the recent independent work by Bovy et al. (2015) but with a different method from ours.

scholarly journals Multi-Wavelength High-Resolution Spectroscopy for Exoplanet Detection: Motivation, Instrumentation and First Results

Geosciences ◽  
2018 ◽  
Vol 8 (8) ◽  
pp. 289 ◽  
Author(s):  
Serena Benatti
Keyword(s):  
High Resolution ◽  
Near Infrared ◽  
Giant Planet ◽  
High Resolution Spectroscopy ◽  
M Dwarfs ◽  
Low Mass Stars ◽  
First Results ◽  
Multi Wavelength ◽  
Low Mass ◽  
Rocky Planets

Exoplanet research has shown an incessant growth since the first claim of a hot giant planet around a solar-like star in the mid-1990s. Today, the new facilities are working to spot the first habitable rocky planets around low-mass stars as a forerunner for the detection of the long-awaited Sun-Earth analog system. All the achievements in this field would not have been possible without the constant development of the technology and of new methods to detect more and more challenging planets. After the consolidation of a top-level instrumentation for high-resolution spectroscopy in the visible wavelength range, a huge effort is now dedicated to reaching the same precision and accuracy in the near-infrared. Actually, observations in this range present several advantages in the search for exoplanets around M dwarfs, known to be the most favorable targets to detect possible habitable planets. They are also characterized by intense stellar activity, which hampers planet detection, but its impact on the radial velocity modulation is mitigated in the infrared. Simultaneous observations in the visible and near-infrared ranges appear to be an even more powerful technique since they provide combined and complementary information, also useful for many other exoplanetary science cases.

scholarly journals A LARGE-SCALE OPTICAL-NEAR-INFRARED SURVEY FOR BROWN DWARFS AND VERY LOW MASS STARS IN THE ORION OB1 ASSOCIATION

2008 ◽  
Vol 136 (1) ◽  
pp. 51-66 ◽  
Author(s):  
Juan José Downes ◽  
César Briceño ◽  
Jesús Hernández ◽  
Nuria Calvet ◽  
Lee Hartmann ◽  
...  
Keyword(s):  
Large Scale ◽  
Near Infrared ◽  
Brown Dwarfs ◽  
Low Mass Stars ◽  
Low Mass ◽  
Infrared Survey

scholarly journals Determining the Physical Properties of Very-Low-Mass Stars and Brown Dwarfs in the Near-Infrared

2009 ◽  
Author(s):  
Emily L. Rice ◽  
Travis S. Barman ◽  
Ian S. McLean ◽  
L. Prato ◽  
J. Davy Kirkpatrick ◽  
...  
Keyword(s):  
Physical Properties ◽  
Near Infrared ◽  
Brown Dwarfs ◽  
Low Mass Stars ◽  
Low Mass

scholarly journals Mass-Luminosity Relations of Very Low Mass Stars

2003 ◽  
Vol 211 ◽  
pp. 413-416 ◽  
Author(s):  
D. Ségransan ◽  
X. Delfosse ◽  
T. Forveille ◽  
J.L. Beuzit ◽  
C. Perrier ◽  
...  
Keyword(s):  
Adaptive Optics ◽  
Main Sequence ◽  
Near Infrared ◽  
Radial Velocities ◽  
Low Mass Stars ◽  
Multiple Stars ◽  
Low Mass

We present new accurate masses at the bottom of the main sequence as well as an improved empirical mass-luminosity relation for very low mass stars in the visible and near infrared. Masses were obtained by combining very accurate radial velocities and adaptive optics images of multiple stars obtained at different orbital phases.

scholarly journals Retrieval of Precise Radial Velocities from Near-infrared High-resolution Spectra of Low-mass Stars

2016 ◽  
Vol 128 (968) ◽  
pp. 104501 ◽  
Author(s):  
Peter Gao ◽  
Plavchan P. ◽  
Gagné J. ◽  
Furlan E. ◽  
Bottom M. ◽  
...  
Keyword(s):  
High Resolution ◽  
Near Infrared ◽  
Radial Velocities ◽  
Low Mass Stars ◽  
Low Mass

scholarly journals The Low-Mass Stellar Luminosity Function of the 30 Dor Starburst Cluster

1998 ◽  
Vol 11 (1) ◽  
pp. 136-136
Author(s):  
Hans Zinnecker
Keyword(s):  
Globular Clusters ◽  
Luminosity Function ◽  
Main Sequence ◽  
Near Infrared ◽  
Young Stellar Objects ◽  
Integration Time ◽  
Low Mass Stars ◽  
Hii Region ◽  
Low Mass ◽  
The Imf

Abstract Diffraction limited near-infrared H-band (1.6 μm) NICMOS HST images are scheduled to be obtained in mid-October 1997 of the young cluster NGC 2070 (age 3.5 Myr) in the 30 Dor giant HII region in the LMC. The aim is to search for the low-mass (M < 2 Mʘ) low-luminosity, red pre-Main Sequence stellar population and to establish the H-band infrared luminosity function. With the NICMOS we can now determine whether the IMF in this prototypical extragalactic starburst cluster is deficient in subsolar low-mass stars or not. The best ground-based data can sample only M > 2 Mʘ. In principle, NICMOS in the H-band (F160W) is sensitive enough to reach a magnitude of ~ 23.5 in a relatively short integration time, which indeed corresponds to the fantastic possibility to detect young stellar objects with masses near the hydrogen burning limit (M=0.1 Mʘ) according to pre-Main Sequence evolutionary models. Even if we could reach only H = 22.5 (i.e. M=0.4 Mʘ), our observations will still go a long way in directly answering, by star counts, whether the IMF in starburst galaxies is low-mass deficient or not, with all the corresponding far-reaching implications. The observations would also tell us whether the 30 Dor cluster can be regarded as a prototype young globular cluster. This possibility would be ruled out, if we found NGC 2070 to be low-mass deficient, because old globular clusters do have a rich population of low-mass stars.

scholarly journals Effect of the rotation, tidal dissipation history and metallicity of stars on the evolution of close-in planets

2019 ◽  
Vol 82 ◽  
pp. 71-79 ◽  
Author(s):  
E. Bolmont ◽  
F. Gallet ◽  
S. Mathis ◽  
C. Charbonnel ◽  
L. Amard
Keyword(s):  
Major Axis ◽  
Semi Major Axis ◽  
Low Mass Stars ◽  
Restoring Force ◽  
Convective Envelope ◽  
Tidal Dissipation ◽  
Rotational Evolution ◽  
Visible Effect ◽  
Low Mass ◽  
The One

Since 1995, numerous close-in planets have been discovered around low-mass stars (M to A-type stars). These systems are susceptible to be tidally evolving, in particular the dissipation of the kinetic energy of tidal flows in the host star may modify its rotational evolution and also shape the orbital architecture of the surrounding planetary system. Recent theoretical studies have shown that the amplitude of the stellar dissipation can vary over several orders of magnitude as the star evolves, and that it also depends on the stellar mass and rotation. We present here one of the first studies of the dynamics of close-in planets orbiting low-mass stars (from 0.6 M☉ to 1.2 M☉) where we compute the simultaneous evolution of the star’s structure, rotation and tidal dissipation in its external convective envelope. We demonstrate that tidal friction due to the stellar dynamical tide, i.e. tidal inertial waves (their restoring force is the Coriolis acceleration) excited in the convection zone, can be larger by several orders of magnitude than the one of the equilibrium tide currently used in celestial mechanics. This is particularly true during the Pre Main Sequence (PMS) phase and to a lesser extent during the Sub Giant (SG) phase. Numerical simulations show that only the high dissipation occurring during the PMS phase has a visible effect on the semi-major axis of close-in planets. We also investigate the effect of the metallicity of the star on the tidal evolution of planets. We find that the higher the metallicity of the star, the higher the dissipation and the larger the tidally-induced migration of the planet.

scholarly journals Near-infrared Variability of Low-mass Stars in IC 1396A and Tr 37

2019 ◽  
Vol 878 (1) ◽  
pp. 7
Author(s):  
Huan Y. A. Meng ◽  
G. H. Rieke ◽  
Jinyoung Serena Kim ◽  
Aurora Sicilia-Aguilar ◽  
N. J. G. Cross ◽  
...  
Keyword(s):  
Near Infrared ◽  
Low Mass Stars ◽  
Low Mass

scholarly journals Disk Mass From Large-Scale Dynamics

1998 ◽  
Vol 11 (1) ◽  
pp. 410-411
Author(s):  
J.A. Sellwood
Keyword(s):  
Dark Matter ◽  
Large Scale ◽  
Stellar Population ◽  
Milky Way ◽  
Low Mass Stars ◽  
Rutgers University ◽  
Disk Mass ◽  
Low Mass ◽  
The Individual ◽  
Inner Parts

The radial distribution of mass in a disk galaxy is strongly constrained by its rotation curve. The separate contributions from the individual stellar populations and dark matter (DM) are not easily disentangled, however, especially since there is generally no feature to indicate where the component dominating the central attraction switches from luminous to dark matter. Here I summarize three recent thesis projects at Rutgers University which all suggest that DM has a low density in the inner parts of bright galaxies, and that most of the mass therefore resides in the disk. In addition, I present some preliminary work on the Milky Way. If we are able to determine the M/L of a typical disk stellar population, it should provide a useful constraint on the numbers of low mass stars.

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