  GEMS and GOODS fields were examined to z~1.4 for galaxy interactions and
mergers. The basic morphologies are familiar: antennae with long tidal tails,
tidal dwarfs, and merged cores; M51-type galaxies with disk spirals and tidal
arm companions; early-type galaxies with diffuse plumes; equal-mass
grazing-collisions; and thick J-shaped tails beaded with star formation and
double cores. One type is not common locally and is apparently a loose
assemblage of smaller galaxies. Photometric measurements were made of the tails
and clumps, and physical sizes were determined assuming photometric redshifts.
Antennae tails are a factor of ~3 smaller in GEMS and GOODS systems compared to
local antennae; their disks are a factor of ~2 smaller than locally. Collisions
among early type galaxies generally show no fine structure in their tails,
indicating that stellar debris is usually not unstable. One exception has a
5x10**9 Msun smooth red clump that could be a pure stellar condensation. Most
tidal dwarfs are blue and probably form by gravitational instabilities in the
gas. One tidal dwarf looks like it existed previously and was incorporated into
the arm tip by tidal forces. The star-forming regions in tidal arms are 10 to
1000 times more massive than star complexes in local galaxies, although their
separations are about the same. If they all form by gravitational
instabilities, then the gaseous velocity dispersions in interacting galaxies
have to be larger than in local galaxies by a factor of ~5 or more; the gas
column densities have to be larger by the square of this factor.
