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The Resolved Stellar Populations of M 32

Published online by Cambridge University Press:  11 July 2011

A. Monachesi
Affiliation:
Kapteyn Astronomical Institute, University of Groningen
S.C. Trager
Affiliation:
Kapteyn Astronomical Institute, University of Groningen
T.R. Lauer
Affiliation:
National Optical Astronomy Observatory
W. Freedman
Affiliation:
The Observatories of the Carnegie Institution of Washington
A. Dressler
Affiliation:
The Observatories of the Carnegie Institution of Washington
C. Grillmair
Affiliation:
Spitzer Science Center
K. Mighell
Affiliation:
National Optical Astronomy Observatory
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Abstract

We present the deepest optical CMD to date of M 32, obtained from HST ACS/HRC images. The dominant feature is the RC, whose CMD location suggests a mean age between 8 and 10 Gyr for [Fe/H] = −0.2 in M 32. We detect for the first time the RGB and AGB bumps in M 32 which constrain its mean age to be 5–10 Gyr old at 2′ from the center. Bright AGB stars indicate the presence of intermediate-age populations. A detected blue component of stars may indicate for the first time the presence of a young stellar population of ~0.5 Gyr in our M 32 field. However, it is likely that the younger stars of this blue plume belong to M 31 rather than to M 32. The fainter stars populating the blue plume indicate the presence of stars not younger than 1 Gyr and/or blue straggler stars in M 32.

Type
Research Article
Copyright
© EAS, EDP Sciences, 2011

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