TY - JOUR
T1 - Phase-space distributions of chemical abundances in Milky Way-type Galaxy halos
AU - Font, Andreea S.
AU - Johnston, Kathryn V.
AU - Bullock, James S.
AU - Robertson, Brant E.
N1 - Copyright:
Copyright 2015 Elsevier B.V., All rights reserved.
PY - 2006/8/1
Y1 - 2006/8/1
N2 - 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 ACDM 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* ∼ 10 9 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 [α/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 [α/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 [α/Fe] ratios below solar.
AB - 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 ACDM 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* ∼ 10 9 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 [α/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 [α/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 [α/Fe] ratios below solar.
KW - Cosmology: theory
KW - Galaxies: abundances
KW - Galaxies: evolution
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U2 - 10.1086/505131
DO - 10.1086/505131
M3 - Article
AN - SCOPUS:33748081113
VL - 646
SP - 886
EP - 898
JO - Astrophysical Journal
JF - Astrophysical Journal
SN - 0004-637X
IS - 2 I
ER -