The Resolved Stellar Populations of M 32

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.