Searching for a Gravitational Heating Signature in Nearby Luminous
  Ellipticals
  We present a new deep optical study of a luminosity limited sample of nearby
elliptical galaxies, attempting to observe the effects of gravitational
interactions on the ISM of these objects. This study is motivated by recent
observations of M86, a nearby elliptical galaxy that shows possible evidence
for gas heating through a recent gravitational interaction. The complete sample
includes luminous ellipticals in clusters, groups and the field. For each of
the galaxies we objectively derive a tidal parameter which measures the
deviation of the stellar body from a smooth, relaxed model and find that 73% of
them show tidal disturbance signatures in their stellar bodies. This is the
first time that such an analysis is done on a statistically complete sample and
it confirms that elliptical galaxies continue to grow and evolve through
gravitational interactions even in the local Universe. Our study of ellipticals
in a wide range of interaction stages, along with available ISM data will
attempt to shed light on this possibly alternative mechanism for maintaining
the observed ISM temperatures of elliptical galaxies.
