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Chemical Abundance Distributions of Galactic Halos and their Satellite Systems in a Lambda CDM Universe

Font, AS, Johnston, KV, Bullock, JS and Robertson, B (2006) Chemical Abundance Distributions of Galactic Halos and their Satellite Systems in a Lambda CDM Universe. The Astrophysical Journal, 638 (2). ISSN 1538-4357

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Abstract

We present a cosmologically motivated model for the hierachical formation of the stellar halo which includes a semi-analytic treatment of galactic chemical enrichment coupled to numerical simulations that track the orbital evolution and tidal disruption of satellites. A major motivating factor in this investigation is the observed systematic difference between the chemical abundances of stars in satellite galaxies and those in the Milky Way halo. Specifically, for the same [Fe/H] values, stars in neighboring satellite galaxies display significantly lower [alpha/Fe] ratios than stars in the halo. We find that the observed chemical abundance patterns are a natural outcome of the process of hierarchical assembly of the Galaxy. This result follows because the stellar halo in this context is built up from satellite galaxies accreted early on (more than 8-9 Gyr ago) and enriched in alpha-elements produced in Type II supernovae. In contrast, satellites which survive today are typically accreted late (within the last 4-5 Gyr) with nearly solar [alpha/Fe] values as a result of contributions from both Type II and Type Ia supernovae. We use our model to investigate the abundance distribution functions (using both [Fe/H] and [alpha/Fe] ratios) for stars in the halo and in surviving satellites. Our results suggest that the shapes and peaks in the abundance distribution functions provide a direct probe of the accretion histories of galaxies.

Item Type: Article
Uncontrolled Keywords: 0201 Astronomical and Space Sciences, 0202 Atomic, Molecular, Nuclear, Particle and Plasma Physics, 0306 Physical Chemistry (incl. Structural)
Subjects: Q Science > QB Astronomy
Q Science > QC Physics
Divisions: Astrophysics Research Institute
Publisher: American Astronomical Society
Related URLs:
Date Deposited: 14 Apr 2020 09:48
Last Modified: 14 Apr 2020 10:00
DOI or Identification number: 10.1086/498970
URI: http://researchonline.ljmu.ac.uk/id/eprint/12718

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