Are Dry Mergers Dry, Moist, or Wet?
  We present a spectral analysis of a sample of red-sequence galaxies
identified by van Dokkum (2005) as dry merger remnants and ongoing dry mergers.
Kinematics, stellar population absorption features, and ionisation from
emission lines, are derived. We find that approximately half of the sample
showing strong tidal features have younger stellar populations than a control
sample at a given velocity dispersion. Conversely, galaxies with weak tidal
tails and/or ongoing mergers -- with the exception of one galaxy -- do not show
this young component. This seems to indicate that the young stellar populations
observed in a significant fraction of ellipticals is the consequence of star
formation triggered by mergers. This young component is consistent with a light
"frosting" of young stars (<2% by mass) superimposed upon a dominant, old (~11
Gyr), stellar population. In terms of stellar populations, these mergers are,
in fact, fairly dry. We found, however, that merger remnants with young stellar
populations are supported by rotation, contrary to the expectations of a major
dry merger. This suggests that the small amount of gas involved has been
sufficient to produce a dynamically cold stellar component. Half of the
galaxies with strong tidal distortion, however, are slow rotating and have
stellar populations compatible with the control sample at a given velocity
dispersion. Remarkably, none of the galaxies with velocity dispersions in
excess of 250 km/s have a young stellar component, independent of the merger
stage.
