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The case for the dual halo of the Milky Way

Title
The case for the dual halo of the Milky Way
Authors
Beers T.C.Carollo D.Ivezic Z.An D.Chiba M.Norris J.E.Freeman K.C.Lee Y.S.Munn J.A.Fiorentin P.R.Sivarani T.Wilhelm R.Yanny B.York D.G.
Ewha Authors
안덕근
SCOPUS Author ID
안덕근scopus
Issue Date
2012
Journal Title
Astrophysical Journal
ISSN
0004-637XJCR Link
Citation
vol. 746, no. 1
Indexed
SCI; SCIE; SCOPUS WOS scopus
Abstract
Carollo et al. have recently resolved the stellar population of the Milky Way halo into at least two distinct components, an inner halo and an outer halo. This result has been criticized by Schönrich et al., who claim that the retrograde signature associated with the outer halo is due to the adoption of faulty distances. We refute this claim, and demonstrate that the Schönrich et al. photometric distances are themselves flawed because they adopted an incorrect main-sequence absolute magnitude relationship from the work of Ivezić et al. When compared to the recommended relation from Ivezić et al., which is tied to a Milky Way globular cluster distance scale and accounts for age and metallicity effects, the relation adopted by Schönrich et al. yields up to 18% shorter distances for stars near the main-sequence turnoff (TO). Use of the correct relationship yields agreement between the distances assigned by Carollo et al. and Ivezić et al. for low-metallicity dwarfs to within 6%-10%. Schönrich et al. also point out that intermediate-gravity stars (3.5 ≤log g < 4.0) with colors redder than the TO region are likely misclassified, with which we concur. We implement a new procedure to reassign luminosity classifications for the TO stars that require it. New derivations of the rotational behavior demonstrate that the retrograde signature and high velocity dispersion of the outer-halo population remain. We summarize additional lines of evidence for a dual halo, including a test of the retrograde signature based on proper motions alone, and conclude that the preponderance of evidence strongly rejects the single-halo interpretation. © 2012. The American Astronomical Society. All rights reserved.
DOI
10.1088/0004-637X/746/1/34
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사범대학 > 과학교육과 > Journal papers
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