Spikes in the SED and Ripples in the Outskirts of Galaxies
  We describe a new method that allows us to quantitatively characterize
galactic satellites from analysis of disturbances in outer gas disks, without
requiring knowledge of their optical light. We have demonstrated the validity
of this method, which we call Tidal Analysis, by applying it to local spirals
with known optical companions, including M51 and NGC 1512. These galaxies span
the range from having a low mass companion (~ one-hundredth the mass of the
primary galaxy) to a fairly massive companion (~ 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 of
the dynamical impact of satellites on galactic disks. Here, we present some
preliminary results on the emergent SEDs and images, calculated along the time
sequence of these dynamical simulations using the 3-D self-consistent Monte
Carlo radiative transfer code RADISHE. We explore star formation prescriptions
and how they affect the emergent SEDs and images. Our goal is to identify SED
colors that are primarily affected by the galaxy's interaction history, and not
significantly affected by the choice of star formation prescription. If
successful, we may be able to utilize the emergent UV-IR SED of the primary
galaxy to understand its recent interaction history.
