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Phase-space distributions of chemical abundances in Milky Way-type Galaxy halos

Font, A.S.; Johnston, K.V.; Bullock, J.S.; Robertson, B.E.

Authors

A.S. Font

K.V. Johnston

J.S. Bullock

B.E. Robertson



Abstract

Motivated by upcoming data from astrometric and spectroscopic surveys of the Galaxy, we explore the chemical abundance properties and phase-space distributions in hierarchically formed stellar halo simulations set in a CDM universe. Our stellar halo metallicities increase with stellar halo mass. The slope of the [Fe/H]-M* trend mimics that of the satellite galaxies that were destroyed to build the halos, implying that the relation propagates hierarchically. All simulated halos contain a significant fraction of old stellar populations accreted more than 10 Gyr ago, and in a few cases some intermediate-age populations exist. In contrast with the Milky Way, many of our simulated stellar halos contain old stellar populations that are metal-rich, originating in the early accretion of massive satellites (M* 109 M). We suggest that the (metal-rich) stellar halo of M31 falls into this category, while the more metal-poor halo of the Milky Way is lacking in early massive accretion events. Interestingly, our hierarchically formed stellar halos often have nonnegligible metallicity gradients in both [Fe/H] and [/Fe]. These gradients extend a few tens of kiloparsecs, and can be as large as 0.5 dex in [Fe/H] and 0.2 dex in [/Fe], with the most metal-poor halo stars typically buried within the central 5 kpc of the galaxy. Finally, we find that chemical abundances can act as a rough substitute for time of accretion of satellite galaxies, and, based on this finding, we propose a criterion for identifying tidal streams spatially by selecting stars with [/Fe] ratios below solar.

Citation

Font, A., Johnston, K., Bullock, J., & Robertson, B. (2006). Phase-space distributions of chemical abundances in Milky Way-type Galaxy halos. Astrophysical Journal, 646(2), 886-898. https://doi.org/10.1086/505131

Journal Article Type Article
Publication Date Aug 1, 2006
Deposit Date Apr 23, 2008
Journal Astrophysical Journal
Print ISSN 0004-637X
Electronic ISSN 1538-4357
Publisher American Astronomical Society
Peer Reviewed Peer Reviewed
Volume 646
Issue 2
Pages 886-898
DOI https://doi.org/10.1086/505131
Keywords Cosmology, Theory, Galaxies, Abundances, Evolution.
Publisher URL http://www.journals.uchicago.edu/ApJ/journal/issues/ApJ/v646n2/64393/brief/64393.abstract.html

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