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THE FRACTIONS OF INNER- AND OUTER-HALO STARS IN THE LOCAL VOLUME

Title
THE FRACTIONS OF INNER- AND OUTER-HALO STARS IN THE LOCAL VOLUME
Authors
An, DeokkeunBeers, Timothy C.Santucci, Rafael M.Carollo, DanielaPlacco, Vinicius M.Lee, Young SunRossi, Silvia
Ewha Authors
안덕근
SCOPUS Author ID
안덕근scopus
Issue Date
2015
Journal Title
ASTROPHYSICAL JOURNAL LETTERS
ISSN
2041-8205JCR Link2041-8213JCR Link
Citation
vol. 813, no. 2
Keywords
Galaxy: abundancesGalaxy: evolutionGalaxy: formationGalaxy: haloGalaxy: stellar content
Publisher
IOP PUBLISHING LTD
Indexed
SCI; SCIE; SCOPUS WOS scopus
Abstract
We obtain a new determination of the metallicity distribution function (MDF) of stars within similar to 5-10 kpc of the Sun, based on recently improved co-adds of ugriz photometry for Stripe. 82 from the Sloan Digital Sky Survey. Our new estimate uses the methodology developed previously by An et al. to study in situ halo stars, but is based on a factor of two larger sample than available before, with much-improved photometric errors and zero-points. The newly obtained MDF can be divided into multiple populations of halo stars, with peak metallicities at [Fe/H] approximate to 1.4 and 1.9, which we associate with the inner-halo and outer-halo populations of the Milky Way, respectively. We find that the kinematics of these stars (based on proper-motion measurements at high Galactic latitude) supports the proposed dichotomy of the halo, as stars with retrograde motions in the rest frame of the Galaxy are generally more metal-poor than stars with prograde motions, consistent with previous claims. In addition, we generate mock catalogs of stars from a simulated Milk Way halo system, and demonstrate for the first time that the chemically and kinematically distinct properties of the inner-and outer-halo populations are qualitatively in agreement with our observations. The decomposition of the observed MDF and our comparison with the mock catalog results suggest that the outer-halo population contributes on the order of similar to 35%-55% of halo stars in the local volume.
DOI
10.1088/2041-8205/813/2/L28
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사범대학 > 과학교육과 > Journal papers
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