The structure of the outer halo of the Galaxy and its relationship to nearby large-scale structure

We present evidence to support an earlier indication that the Galaxy is embedded in an extended, highly inclined, triaxial halo outlined by the spatial distribution of companion galaxies to the Milky Way. Signatures of this spatial distribution are seen in (1) the angular variation of the radial velocity dispersion of the companion galaxies, (2) the spatial distribution of the M31 subgroup of galaxies, (3) the spatial distribution of the isolated (mainly dwarf irregular) galaxies of the Local Group, (4) the velocity anisotropy quadrupole of a subgroup of high-velocity clouds, and (5) the spatial distribution of galaxies in the Coma-Sculptor cloud. Tidal effects of M31 and surrounding galaxies on the Galaxy are not strong enough to have affected the observed structure. We conclude that this distribution is a reflection of initial conditions. A simple galaxy formation scenario is proposed that relates the results found here to those of Holmberg and Zaritsky et al. regarding the peculiar distribution of satellites around a large sample of spiral galaxies.