skip to main content

SciTech ConnectSciTech Connect

Title: Possible evidence for metal accretion onto the surfaces of metal-poor main-sequence stars

The entire evolution of the Milky Way, including its mass-assembly and star-formation history, is imprinted onto the chemo-dynamical distribution function of its member stars, f(x, v, [X/H]), in the multi-dimensional phase space spanned by position, velocity, and elemental abundance ratios. In particular, the chemo-dynamical distribution functions for low-mass stars (e.g., G- or K-type dwarfs) are precious tracers of the earliest stages of the Milky Way's formation, since their main-sequence lifetimes approach or exceed the age of the universe. A basic tenet of essentially all previous analyses is that the stellar metallicity, usually parameterized as [Fe/H], is conserved over time for main-sequence stars (at least those that have not been polluted due to mass transfer from binary companions). If this holds true, any correlations between metallicity and kinematics for long-lived main-sequence stars of different masses, effective temperatures, or spectral types must strictly be the same, since they reflect the same mass-assembly and star-formation histories. By analyzing a sample of nearby metal-poor halo and thick-disk stars on the main sequence, taken from Data Release 8 of the Sloan Digital Sky Survey, we find that the median metallicity of G-type dwarfs is systematically higher (by about 0.2 dex) than that of K-type dwarfsmore » having the same median rotational velocity about the Galactic center. If it can be confirmed, this finding may invalidate the long-accepted assumption that the atmospheric metallicities of long-lived stars are conserved over time.« less
Authors:
;  [1] ;  [2] ;  [3] ;  [4]
  1. Institute of Astronomy, School of Science, University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015 (Japan)
  2. National Optical Astronomy Observatories, Tucson, AZ 85719 (United States)
  3. Department of Physics and Astronomy, Macquarie University, Sydney, 2109 NSW (Australia)
  4. Department of Astronomy, New Mexico State University, Las Cruces, NM 88003 (United States)
Publication Date:
OSTI Identifier:
22357221
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 784; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABUNDANCE; CORRELATIONS; DISTRIBUTION FUNCTIONS; EVOLUTION; LIFETIME; MAIN SEQUENCE STARS; MASS TRANSFER; METALLICITY; METALS; MILKY WAY; SURFACES; UNIVERSE; VELOCITY