Next Contents


The Local Group hosts three spiral galaxies: the Milky Way, M31, and M33. The Milky Way and M31 are the only massive galaxies in the Local Group, and there are indications that M31 is more representative of massive spirals than the Milky Way (e.g. Hammer et al. 2007). While M33 is the third most massive galaxy in the Local Group, it is a distant third (van den Bergh 2000), and it is representative of the most common type of spiral galaxy in the local universe (see Marinoni et al. 1999). Because M31 and M33 are at respective distances of 770 kpc (Freedman & Madore 1990) and 860 kpc (Sarajedini et al. 2006), we can obtain photometry of their resolved stellar populations and thus constrain their star formation histories at a fidelity exceeding that possible in the Milky Way, where such studies of the field population are often hampered by distance and reddening uncertainties. Here, I review the observational constraints on the spheroid (bulge and halo) populations of these galaxies.