Internal Kinematics of Field Galaxies at Intermediate Redshifts

This paper describes the results of a survey of the internal kinematics of intermediate-redshift (z \ 0.250.45) eld galaxies. Spatially resolved spectra of the [O II] jj3726, 3729 doublet emission line have been obtained for 22 galaxies at the Canada-France-Hawaii Telescope. High spatial resolution has made it possible to extract and [O II] disk scale lengths from each galaxy spectrum using syn-V rot sin i thetic galaxy rotation curve tting. About 25% of the galaxies in the sample have [O II] kinematics unrelated to rotation. [O II] emission is concentrated in the nucleus in these "" kinematically anomalous galaxies. A Doppler ellipse, similar to those found in local dwarf irregular galaxies, has been observed in a z \ 0.35 galaxy. An intermediate-redshift Tully-Fisher (TF) relation, dened by 12 kinematically normal galaxies, shows that these galaxies have a systematically lower rotation velocity (i.e., mass) for their luminosity than expected from the local TF relation. These galaxies would have to fade by D1.52 mag to lie on the local TF relation. This is consistent with starbursting dwarf galaxy models. Although the sample is small, there is also a hint that massive galaxies are not as displaced from the local TF relation as low-mass ones. However, as shown using a large sample of local galaxies, the scatter in the local TF relation is large, especially for late-type galaxies. Sample selection e ects, particularly in [O II] emission strength, could be responsible for part of the observed TF evolutionary shift if star formation rates were responsible for the local TF relation scatter. A comparison with other works indicates that a mass-dependent luminosity evolution scenario can explain almost all of the available internal kinematics and surface brightness data.