Hitting the Bull's-eye: The Radial Profile of Accretion and Star
  Formation in the Milky Way
  Ongoing star formation in the Milky Way requires continuous gaseous fuel from
accretion. Previous work has suggested that the accretion of dwarf galaxies
could provide the needed gas for this process. In this work we investigate
whether dwarf galaxy accretion is consistent with the radial profile of star
formation observed in the Milky Way, which is strongly concentrated toward the
center of the gaseous disk of the Galaxy. Using realistic parameters for the
Galactic potential, gaseous halo, Galactic disk, velocities of dwarf galaxies,
and effects of drag on stripped gas in the halo, we model the distribution of
radii at which dwarf galaxies accrete onto the Galactic disk. We also model the
radial distribution of the accretion of gas that cools directly out of the halo
by examining the results of recent simulations. We show that dwarf galaxies
cannot reproduce the concentration of accretion toward the center of the Galaxy
required by star formation. We also show that clouds that cool directly from
the halo can reproduce this central concentration, and conclude that this
difference is largely due to the discrepancy in absolute specific angular
momentum between the two mechanisms.
