A Survey of Galaxy Kinematics to z ~ 1 in the TKRS/GOODS-N Field. I. Rotation and Dispersion Properties

Abstract

We present kinematic measurements of a large sample of galaxies from the TKRS Survey in the GOODS-N field. We measure line-of-sight velocity dispersions from integrated emission for 1089 galaxies with median z=0.637, and spatially resolved kinematics for a subsample of 380 galaxies. This is the largest sample of galaxies to z ~ 1 with kinematics to date, and allows us to measure kinematic properties without morphological pre-selection. Emission linewidths provide kinematics for the bulk of blue galaxies. To fit the spatially resolved kinematics, we fit models with both line-of-sight rotation amplitude and velocity dispersion. Integrated linewidth correlates well with a combination of the rotation gradient and dispersion, and is a robust measure of galaxy kinematics. The spatial extents of emission and continuum are similar and there is no evidence that linewidths are affected by nuclear or clumpy emission. The measured rotation gradient depends strongly on slit PA alignment with galaxy major axis, but integrated linewidth does not. Even for galaxies with well-aligned slits, some have kinematics dominated by dispersion (V/sigma<1) rather than rotation. These are probably objects with disordered velocity fields, not dynamically hot stellar systems. About 35% of the resolved sample are dispersion dominated; galaxies that are both dispersion dominated and bright exist at high redshift but appear rare at low redshift. This kinematic morphology is linked to photometric morphology in HST/ACS images: dispersion dominated galaxies include a higher fraction of irregulars and chain galaxies, while rotation dominated galaxies are mostly disks and irregulars. Only one-third of chain/hyphen galaxies are dominated by rotation; high-z elongated objects cannot be assumed to be inclined disks. (Abridged)