Kinematic and Structural Evolution of Field and Cluster Spiral Galaxies
  To understand the processes that build up galaxies we investigate the stellar
structure and gas kinematics of spiral and irregular galaxies out to redshift
1. We target 92 galaxies in four cluster (z = 0.3 & 0.5) fields to study the
environmental influence. Their stellar masses derived from multiband VLT/FORS
photometry are distributed around but mostly below the characteristic
Schechter-fit mass. From HST/ACS images we determine morphologies and
structural parameters like disk length, position angle and ellipticity.
Combining the spectra of three slit positions per galaxy using the MXU mode of
VLT/FORS2 we construct the two-dimensional velocity field from gas emission
lines for 16 cluster members and 33 field galaxies. The kinematic position
angle and flatness are derived by a Fourier expansion of elliptical velocity
profiles. To trace possible interaction processes, we define three irregularity
indicators based on an identical analysis of local galaxies from the SINGS
project. Our distant sample displays a higher fraction of disturbed velocity
fields with varying percentages (10%, 30% and 70%) because they trace different
features. While we find far fewer candidates for major mergers than the SINS
sample at z~2, our data are sensitive enough to trace less violent processes.
Most irregular signatures are related to star formation events and less massive
disks are affected more than Milky-Way type objects. We detect similarly high
fractions of irregular objects both for the distant field and cluster galaxies
with similar distributions. We conclude that we may witness the building-up of
disk galaxies still at redshifts z~0.5 via minor mergers and gas accretion,
while some cluster members may additionally experience stripping, evaporation
or harassment interactions.
