An HST/ACS view of the inhomogeneous outer halo of M31

J. C. Richardson, A. M. N. Ferguson, A. D. Mackey, M. J. Irwin, S. C. Chapman, A. Huxor, R. A. Ibata, G. F. Lewis, N. R. Tanvir, Annette Ferguson

Research output: Contribution to journalArticlepeer-review


We present a high precision photometric view of the stellar populations in the outer halo of M31, using data taken with the Hubble Space Telescope/Advanced Camera for Surveys. We analyse the field populations adjacent to 11 luminous globular clusters which sample the galactocentric radial range 18 ~ -0.6 to -1.0dex and considerable metallicity dispersions of 0.2 to 0.3dex (assuming a 10 Gyr population and scaled-solar abundances). The average metallicity over the range 30-60kpc is [Fe/H] = -0.80 +/- 0.14dex, with no evidence for a significant radial gradient. Metal-poor stars ([Fe/H]
Original languageEnglish
Pages (from-to)1842-1850
JournalMonthly Notices of the Royal Astronomical Society
Publication statusPublished - 1 Jul 2009


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