Young accreted globular clusters in the outer halo of m31

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DOIResolve DOI: http://doi.org/10.1093/mnras/sts336
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TypeArticle
Journal titleMonthly Notices of the Royal Astronomical Society
ISSN0035-8711
Volume429
Issue1
Pages281293; # of pages: 13
AbstractWe report on observations of two newly discovered globular clusters in the outskirts of M31 made using the Gemini Multi-Object Spectrograph (GMOS) instrument on Gemini North. These objects, PAndAS-7 (PA-7) and PAndAS-8 (PA-8), lie at a galactocentric radius of 87 kpc and are projected, with separation 19 kpc, on to a field halo substructure known as the South-West Cloud. We measure radial velocities for the two clusters which confirm that they are almost certainly physically associated with this feature. Colour-magnitude diagrams reveal strikingly short, exclusively red horizontal branches in both PA-7 and PA-8; both also have photometric [Fe/H]=-1.35±0.15. At this metallicity, the morphology of the horizontal branch is maximally sensitive to age, and we use the distinctive configurations seen in PA-7 and PA-8 to demonstrate that both objects are very likely to be at least 2 Gyr younger than the oldest Milky Way globular clusters. Our observations provide strong evidence for young globular clusters being accreted into the remote outer regions of M31 in a manner entirely consistent with the established picture for the Milky Way, and add credence to the idea that similar processes play a central role in determining the composition of globular cluster systems in large spiral galaxies in general. ©2012 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.
Publication date
LanguageEnglish
AffiliationNational Research Council Canada (NRC-CNRC); National Science Infrastructure
Peer reviewedYes
NPARC number21271834
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Record identifier4c32742c-0737-4749-a671-36bb72eba52d
Record created2014-04-23
Record modified2016-05-09
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