Galaxy Pairs in COSMOS -- Merger Rate Evolution Since z=1
  We present results of a statistical study of the cosmic evolution of the mass
dependent major-merger rate since z=1. A stellar mass limited sample of close
major-merger pairs (the CPAIR sample) was selected from the archive of the
COSMOS survey. Pair fractions at different redshifts derived using the CPAIR
sample and a local K-band selected pair sample show no significant variations
with stellar mass. The pair fraction exhibits moderately strong cosmic
evolution, with the best-fitting evolutionary index m=2.2+-0.2. The
best-fitting function for the merger rate implies that galaxies with stellar
mass between 1E+10 -- 3E+11 M_sun have undergone 0.5 -- 1.5 major-mergers since
z=1. Our results show that, for massive galaxies at z<1, major mergers
involving star forming galaxies (i.e. wet and mixed mergers) can account for
the formation of both ellipticals and red quiescent galaxies (RQGs). On the
other hand, major mergers cannot be responsible for the formation of most low
mass ellipticals and RQGs. Our quantitative estimates indicate that major
mergers have significant impact on the stellar mass assembly of the most
massive galaxies, but for less massive galaxies the stellar mass assembly is
dominated by the star formation. Comparison with the mass dependent (U)LIRG
rates suggests that the frequency of major-merger events is comparable to or
higher than that of (U)LIRGs.
