PAndAS' progeny: extending the M31 dwarf galaxy cabal
  We present the discovery of five new dwarf galaxies, Andromeda XXIII-XXVII,
located in the outer halo of M31. These galaxies were found in the second year
of data from the Pan-Andromeda Archaeological Survey (PAndAS) of the M31/M33
subgroup. This survey now provides an almost complete panoramic view of the M31
halo out to an average projected radius of ~150 kpc. The metal-poor stellar
density map for this whole region serves, not only as an illustration of the
discovery space for satellite galaxies, but also gives a birds-eye view of the
ongoing assembly process of an L* disk galaxy. Four of the new dwarfs appear as
well-defined spatial over-densities of stars lying on the expected locus of
metal-poor red giant branch stars at the distance of M31. The fifth
over-density, And XXVII, is embedded in an extensive stream of such stars and
is possibly the remnant of a strong tidal disruption event. All five satellites
have metallicities and luminosities typical of dwarf spheroidal galaxies and
continue the trend whereby the brighter dwarf spheroidal satellites of M31
generally have much larger half-light radii than their Milky Way counterparts.
With an extended sample of M31 satellite galaxies we also revisit the spatial
distribution of this population and find that, within the current limits of the
PAndAS survey, the surface density of satellites is essentially constant out to
150 kpc. This corresponds to a radial density distribution of satellites
varying as 1/r, a result seemingly in conflict with the predictions of
cosmological simulations. (Abridged)
