We report the serendipitous discovery of a faint globular cluster found on archival Hubble Space Telescope images of Andromeda I, a dwarf spheroidal (dSph) companion of M31. Of the 17 dSph galaxies in the Local Group, only the two brightest companions of the Milky Way were previously known to contain globular clusters, while none had been found in M31's six dSph satellites. And I is the least luminous galaxy in which a globular cluster has been detected so far. The horizontal branch luminosity of the globular cluster puts it at the same distance as And I though we cannot exclude that we are seeing an outlying globular cluster of M31 projected against, and physically very close to, And I. The globular cluster appears to be of similar age and metallicity as the underlying field population in And I. Assuming membership, the resulting specific globular cluster frequency for And I is SN ~ 19. The cluster resembles the sparse outer halo globular clusters found around the Milky Way and lies just outside the core radius of And I.
Astronomische Gesellschaft Meeting Abstracts
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