The Stellar Populations of M32: Resolving the nearest elliptical with HST ACS/HRC

Abstract

Abstract. We present the deepest colour-magnitude diagram (CMD) of M32 to date, obtained from deep (F435W, F555W) photometry of HST ACS/HRC images. Due to the high resolution of our images, the small photometric errors, and the completeness level of our data we obtain the most detailed resolved photometric study of M32 to date. The CMD of M32 displays a wide colour distribution of red giant branch stars, mainly due to a metallicity spread, a strong red clump and bright asymptotic giant branch stars. The detection of a "blue plume" in M32 indicates the presence of a very young stellar population. There is not a noticeable presence of blue horizontal branch stars, suggesting that an old population with [Fe/H] < −1.5 does not significantly contribute to the light or mass of M32 in our observed fields.