The spatially-resolved star formation history of the M31 outer disc

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DOIResolve DOI: http://doi.org/10.1093/mnrasl/slv116
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TypeArticle
Journal titleMonthly Notices of the Royal Astronomical Society: Letters
ISSN1745-3925
1745-3933
Volume453
Issue1
PagesL113L117
Subjectgalaxies: evolution; galaxies: formation; galaxies: individual: M31; local group; galaxies: stellar content; galaxies: structure
AbstractWe present deep Hubble Space Telescope Advanced Camera for Surveys observations of the stellar populations in two fields lying at 20 and 23 kpc from the centre of M31 along the south-west semimajor axis. These data enable the construction of colour–magnitude diagrams reaching the oldest main-sequence turn-offs (∼13 Gyr) which, when combined with another field at 25 kpc from our previous work, we use to derive the first precision constraints on the spatially-resolved star formation history of the M31 disc. The star formation rates exhibit temporal as well as field-to-field variations, but are generally always within a factor of 2 of their time average. There is no evidence of inside-out growth over the radial range probed. We find a median age of ∼7.5 Gyr, indicating that roughly half of the stellar mass in the M31 outer disc was formed before z ∼ 1. We also find that the age–metallicity relations (AMRs) are smoothly increasing from [Fe/H] ≃ −0.4 to solar metallicity between 10 and 3 Gyr ago, contrary to the flat AMR of the Milky Way disc at a similar number of scalelengths. Our findings provide insight on the roles of stellar feedback and radial migration in the formation and evolution of large disc galaxies.
Publication date
PublisherMonthly Notices of the Royal Astronomical Society
LanguageEnglish
AffiliationNRC Herzberg Astronomy and Astrophysics; National Research Council Canada
Peer reviewedYes
NPARC number23001694
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Record identifiere6a81c88-07e0-4835-b61c-88d3952934f4
Record created2017-03-20
Record modified2017-03-30
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