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Chemical evolution of the Galactic bulge as traced by microlensed dwarf and subgiant stars : V. Evidence for a wide age distribution and a complex MDF

Bensby, T; Yee, J C; Feltzing, Sofia; Johnson, Jennifer A; Gould, A; Cohen, Judith G; Asplund, Martin; Melendez, Jorge; Lucatello, Sara; Han, C; Thompson, Ian; Gal-Yam, Avishay; Udalski, A; Bennett, D P; Bond, I; Kohei, W

Description

Based on high-resolution spectra obtained during gravitational microlensing events we present a detailed elemental abundance analysis of 32 dwarf and subgiant stars in the Galactic bulge. Combined with the sample of 26 stars from the previous papers in this series, we now have 58 microlensed bulge dwarfs and subgiants that have been homogeneously analysed. The main characteristics of the sample and the findings that can be drawn are: (i) the metallicity distribution (MDF) is wide and spans all...[Show more]

dc.contributor.authorBensby, T
dc.contributor.authorYee, J C
dc.contributor.authorFeltzing, Sofia
dc.contributor.authorJohnson, Jennifer A
dc.contributor.authorGould, A
dc.contributor.authorCohen, Judith G
dc.contributor.authorAsplund, Martin
dc.contributor.authorMelendez, Jorge
dc.contributor.authorLucatello, Sara
dc.contributor.authorHan, C
dc.contributor.authorThompson, Ian
dc.contributor.authorGal-Yam, Avishay
dc.contributor.authorUdalski, A
dc.contributor.authorBennett, D P
dc.contributor.authorBond, I
dc.contributor.authorKohei, W
dc.date.accessioned2015-12-13T22:15:49Z
dc.identifier.issn0004-6361
dc.identifier.urihttp://hdl.handle.net/1885/70577
dc.description.abstractBased on high-resolution spectra obtained during gravitational microlensing events we present a detailed elemental abundance analysis of 32 dwarf and subgiant stars in the Galactic bulge. Combined with the sample of 26 stars from the previous papers in this series, we now have 58 microlensed bulge dwarfs and subgiants that have been homogeneously analysed. The main characteristics of the sample and the findings that can be drawn are: (i) the metallicity distribution (MDF) is wide and spans all metallicities between [Fe/H] = -1.9 to +0.6; (ii) the dip in the MDF around solar metallicity that was apparent in our previous analysis of a smaller sample (26 microlensed stars) is no longer evident; instead it has a complex structure and indications of multiple components are starting to emerge. A tentative interpretation is that there could be different stellar populations at interplay, each with a different scale height: the thin disk, the thick disk, and a bar population; (iii) the stars with [Fe/H] ≤ -0.1 are old with ages between 10 and 12 Gyr; (iv) the metal-rich stars with [Fe/H] ≥ -0.1 show a wide variety of ages, ranging from 2 to 12 Gyr with a distribution that has a dominant peak around 4-5 Gyr and a tail towards higher ages; (v) there are indications in the [α/Fe]-[Fe/H] abundance trends that the "knee" occurs around [Fe/H] = -0.3to -0.2, which is a slightly higher metallicity as compared to the "knee" for the local thick disk. This suggests that the chemical enrichment of the metal-poor bulge has been somewhat faster than what is observed for the local thick disk. The results from the microlensed bulge dwarf stars in combination with other findings in the literature, in particular the evidence that the bulge has cylindrical rotation, indicate that the Milky Way could be an almost pure disk galaxy. The bulge would then just be a conglomerate of the other Galactic stellar populations (thin disk, thick disk, halo, and.?), residing together in the central parts of the Galaxy, influenced by the Galactic bar.
dc.publisherSpringer
dc.rightsAuthor/s retain copyright
dc.sourceAstronomy and Astrophysics
dc.subjectKeywords: Galaxy: bulge; Galaxy: evolution; Galaxy: formation; Gravitational lensing; Stars: abundances; Astrophysics; Galaxies; Stars Galaxy: bulge; Galaxy: evolution; Galaxy: formation; Gravitational lensing: micro; Stars: abundances
dc.titleChemical evolution of the Galactic bulge as traced by microlensed dwarf and subgiant stars : V. Evidence for a wide age distribution and a complex MDF
dc.typeJournal article
local.description.notesImported from ARIES
local.identifier.citationvolume549
dc.date.issued2013
local.identifier.absfor020100 - ASTRONOMICAL AND SPACE SCIENCES
local.identifier.ariespublicationf5625xPUB2351
local.type.statusPublished Version
local.contributor.affiliationBensby, T, Lund Observatory
local.contributor.affiliationYee, J C, Ohio State University
local.contributor.affiliationFeltzing, Sofia, Lund Observatory
local.contributor.affiliationJohnson, Jennifer A, Ohio State University
local.contributor.affiliationGould, A, Ohio State University
local.contributor.affiliationCohen, Judith G, California Institute of Technology
local.contributor.affiliationAsplund, Martin, College of Physical and Mathematical Sciences, ANU
local.contributor.affiliationMelendez, Jorge, University of Sao Paulo
local.contributor.affiliationLucatello, Sara, INAF, Osservatorio Astronomico di Padova
local.contributor.affiliationHan, C, Chungbuk National University
local.contributor.affiliationThompson, Ian, Observatories of the Carnegie Institution of Washington
local.contributor.affiliationGal-Yam, Avishay, Weizmann Institute of Science
local.contributor.affiliationUdalski, A, Warsaw University Observatory
local.contributor.affiliationBennett, D P, University of Notre Dame
local.contributor.affiliationBond, I, Massey University
local.contributor.affiliationKohei, W, Osaka University
local.bibliographicCitation.startpageA147/1
local.bibliographicCitation.lastpage26
local.identifier.doi10.1051/0004-6361/201220678
dc.date.updated2016-02-24T08:56:58Z
local.identifier.scopusID2-s2.0-84872578931
local.identifier.thomsonID000313745000147
dcterms.accessRightsOpen Access
CollectionsANU Research Publications

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