The structures and total (minor + major) merger histories of massive
  galaxies up to z = 3 in the HST GOODS NICMOS Survey: A possible solution to
  the size evolution problem
  We investigate the total major (> 1:4 by stellar mass) and minor (> 1:100 by
stellar mass) merger history of a population of 80 massive (M_* > 10^11 M_sol)
galaxies at high redshifts (z = 1.7 - 3). We utilize extremely deep and high
resolution HST H-band imaging from the GOODS NICMOS Survey (GNS), which
corresponds to rest-frame optical wavelengths at the redshifts probed. We find
that massive galaxies at high redshifts are often morphologically disturbed,
with a CAS deduced merger fraction f_m = 0.23 +/- 0.05 at z = 1.7 - 3. We find
close accord between close pair methods (within 30 kpc apertures) and CAS
methods for deducing major merger fractions at all redshifts. We deduce the
total (minor + major) merger history of massive galaxies with M_* > 10^9 M_sol
galaxies, and find that this scales roughly linearly with log-stellar-mass and
magnitude range. We test our close pair methods by utilizing mock galaxy
catalogs from the Millennium Simulation. We compute the total number of mergers
to be (4.5 +/- 2.9) / <\tau_m> from z = 3 to the present, to a stellar mass
sensitivity threshold of ~ 1:100 (where \tau_m is the merger timescale in Gyr
which varies as a function of mass). This corresponds to an average mass
increase of (3.4 +/- 2.2) x 10^11 M_sol over the past 11.5 Gyrs due to merging.
We show that the size evolution observed for these galaxies may be mostly
explained by this merging.
