Finding Dwarf Galaxies From Their Tidal Imprints
  We describe ongoing work on a new method that allows one to determine the
mass and relative position (in galactocentric radius and azimuth) of galactic
companions purely from analysis of observed disturbances in gas disks. Here, we
demonstrate the validity of this method, which we call Tidal Analysis, by
applying it to local spirals with known optical companions, namely M51 and NGC
1512. These galaxies span the range from having a very low mass companion
($\sim$ one-hundredth the mass of the primary galaxy) to a fairly massive
companion ($\sim$ one-third the mass of the primary galaxy). This approach has
broad implications for many areas of astrophysics -- for the indirect detection
of dark matter (or dark-matter dominated dwarf galaxies), and for galaxy
evolution in its use as a decipher for the dynamical impact of satellites on
galactic disks. Here, we provide a proof of principle of the method by applying
it to infer and quantitatively characterize optically visible galactic
companions of local spirals, from the analysis of observed disturbances in
outer gas disks.
