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 isembedded in an extended, highly inclined, triaxial halo outlined by the spatialdistribution of companion galaxies to the Milky Way. Signatures of this spatialdistribution are seen in 1) the angular variation of the radial-velocitydispersion of the companion galaxies, 2) the spatial distribution of the M~31sub-group of galaxies, 3) the spatial distribution of the isolated, mainlydwarf irregular, galaxies of the Local Group, 4) the velocity anisotropyquadrupole of a sub-group of high-velocity clouds, and 5) the spatialdistribution of galaxies in the Coma-Sculptor cloud. Tidal effects of M~31 andsurrounding galaxies on the Galaxy are not strong enough to have affected theobserved structure. We conclude that this distribution is a reflection ofinitial conditions. A simple galaxy formation scenario is proposed which tiestogether the results found here with those of Holmberg (1969) and Zaritsky etal. (1997) on the peculiar distribution of satellites around a large sample ofspiral galaxies.Comment: Accepted for publication in the Astron J., March 2000, 12 pages with 1 figur