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[α/Fe] Abundances of Four Outer M31 Halo Stars

Vargas, Luis C. and Gilbert, Karoline M. and Geha, Marla and Tollerud, Erik J. and Kirby, Evan N. and Guhathakurta, Puragra (2014) [α/Fe] Abundances of Four Outer M31 Halo Stars. Astrophysical Journal Letters, 797 (1). Art. No. L2. ISSN 2041-8205. doi:10.1088/2041-8205/797/1/L2.

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We present alpha element to iron abundance ratios, [α/Fe], for four stars in the outer stellar halo of the Andromeda Galaxy (M31). The stars were identified as high-likelihood field halo stars by Gilbert et al. and lie at projected distances between 70 and 140 kpc from M31's center. These are the first alpha abundances measured for a halo star in a galaxy beyond the Milky Way. The stars range in metallicity between [Fe/H] = –2.2 and [Fe/H] = –1.4. The sample's average [α/Fe] ratio is +0.20 ± 0.20. The best-fit average value is elevated above solar, which is consistent with rapid chemical enrichment from Type II supernovae. The mean [α/Fe] ratio of our M31 outer halo sample agrees (within the uncertainties) with that of Milky Way inner/outer halo stars that have a comparable range of [Fe/H].

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Vargas, Luis C.0000-0001-7155-0040
Gilbert, Karoline M.0000-0003-0394-8377
Geha, Marla0000-0002-7007-9725
Tollerud, Erik J.0000-0002-9599-310X
Kirby, Evan N.0000-0001-6196-5162
Guhathakurta, Puragra0000-0001-8867-4234
Additional Information:© 2014 American Astronomical Society. Received 2014 August 25; accepted 2014 November 6; published 2014 November 20. L.C.V. acknowledges useful conversations with Nikhil Padmanabhan during the analysis stage of this project. L.C.V. was supported by the NSF Graduate Research Fellowship (Grant DGE−1122492). M.G. and L.C.V. acknowledge support from NSF Grant AST−0908752, and P.G. acknowledges support from NSF grant AST−1010039. E.J.T. and K.G. were supported by NASA through Hubble Fellowship Grant Nos. 51316.01 and 51273.01, awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS 5-26555. Facility: Keck:II (DEIMOS)
Funding AgencyGrant Number
NSF Graduate Research FellowshipDGE−1122492
Space Telescope Science InstituteUNSPECIFIED
NASANAS 5-26555
Subject Keywords:galaxies: abundances; galaxies: evolution; galaxies: individual (M31); Local Group
Issue or Number:1
Record Number:CaltechAUTHORS:20141217-104619921
Persistent URL:
Official Citation:[α/Fe] Abundances of Four Outer M31 Halo Stars Luis C. Vargas et al. 2014 ApJ 797 L2
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:52957
Deposited By: Ruth Sustaita
Deposited On:17 Dec 2014 19:22
Last Modified:10 Nov 2021 19:46

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