The DiskMass Survey. VI. Gas and stellar kinematics in spiral galaxies
  from PPak integral-field spectroscopy
  We present ionized-gas (OIII) and stellar kinematics (velocities and velocity
dispersions) for 30 nearly face-on spiral galaxies out to as much as three disk
scale lengths (h_R). These data have been derived from PPak IFU spectroscopy
(4980-5370A), observed at a mean resolution of R=7700 (sigma_inst=17km/s).
These data are a fundamental product of our survey and will be used in
companion papers to, e.g., derive the detailed (baryonic+dark) mass budget of
each galaxy in our sample. Our presentation provides a comprehensive
description of the observing strategy, data reduction, and analysis. Along with
a clear presentation of the data, we demonstrate: (1) The OIII and stellar
rotation curves exhibit a clear signature of asymmetric drift with a rotation
difference that is 11% of the maximum rotation speed of the galaxy disk,
comparable to measurements in the solar neighborhood in the Milky Way. (2) The
e-folding length of the stellar velocity dispersion is two times h_R on
average, as expected for a disk with a constant scale height and mass-to-light
ratio, with a scatter that is notably smaller for massive,
high-surface-brightness disks in the most luminous galaxies. (3) At radii
larger than 1.5 h_R, the stellar velocity dispersion tends to decline slower
than the best-fitting exponential function, which may be due to an increase in
the disk mass-to-light ratio, disk flaring, or disk heating by the dark-matter
halo. (4) A strong correlation exists between the central vertical stellar
velocity dispersion of the disks and their circular rotational speed at 2.2
h_R, with a zero point indicating that galaxy disks are submaximal. Moreover,
weak but consistent correlations exist such that disks with a fainter central
surface brightness in bluer and less luminous galaxies of later morphological
types are kinematically colder with respect to their rotational velocities.
