The Space Density Evolution of Wet and Dry Mergers in the
  Canada-France-Hawaii Telescope Legacy Survey
  We analyze 1298 merging galaxies with redshifts up to z=0.7 from the
Canada-France-Hawaii Telescope Legacy Survey, taken from the catalog presented
in Bridge et al. (2010). By analyzing the internal colors of these systems, we
show that so-called wet and dry mergers evolve in different senses, and
quantify the space densities of these systems. The local space density of wet
mergers is essentially dentical to the local space density of dry mergers. The
evolution in the total merger rate is modest out to z ~ 0.7, although the wet
and dry populations have different evolutionary trends. At higher redshifts dry
mergers make a smaller contribution to the total merging galaxy population, but
this is offset by a roughly equivalent increase in the contribution from wet
mergers. By comparing the mass density function of early-type galaxies to the
corresponding mass density function for merging systems, we show that not all
the major mergers with the highest masses (M_stellar > 10^11 M_solar) will end
up with the most massive early-type galaxies, unless the merging timescale is
dramatically longer than that usually assumed. On the other hand, the
usually-assumed merging timescale of ~ 0.5-1 Gyr is quite consistent with the
data if we suppose that only less massive early-type galaxies form via mergers.
Since low-intermediate mass ellipticals are 10 --100 times more common than
their most massive counterparts, the hierarchical explanation for the origin of
early-type galaxies may be correct for the vast majority of early-types, even
if incorrect for the most massive ones.
