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

We present kinematic measurements of a large sample of galaxies from the Team Keck Redshift Survey in the GOODS-N field. We measure line-of-sight velocity dispersions from integrated emission for 1089 galaxies with median redshift 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 preselection. Emission-line widths provide a dynamical measurement for the bulk of blue galaxies. To fit the spatially resolved kinematics, we construct models that fit both line-of-sight rotation amplitude and velocity dispersion. Integrated line width correlates well with a combination of the velocity 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 line widths are affected by nuclear or clumpy emission. The measured rotation gradient depends strongly on slit position angle alignment with galaxy major axis, but integrated line width does not. Even for galaxies with well-aligned slits, some have kinematics dominated by dispersion (V/σ<1) rather than rotation. These are probably objects with disordered velocity fields, not dynamically hot stellar systems. About 35% of the spatially 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 may probe galaxies' evolutionary state. It 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-redshift elongated objects cannot be assumed to be inclined disks.

Based in part on observations taken at the W. M. Keck Observatory, which is operated jointly by the University of California and the California Institute of Technology.