The evolution of early-type galaxies in distant clusters. II. Internal kinematics of 55 galaxies in the z=0.33 cluster Cl 1358+62

We define a large sample of galaxies for use in a study of the fundamental plane in the intermediate redshift cluster Cl 1358 + 62 at z = 0.33. We have analyzed high-resolution spectra for 55 members of the cluster. The data were acquired with the Low-Resolution Imaging Spectrograph on the Keck 1 10 m telescope. A new algorithm for measuring velocity dispersions is presented and used to measure the internal kinematics of the galaxies. This algorithm has been tested against the Fourier fitting method so that the data presented here can be compared with those measured previously in nearby galaxies. We have measured central velocity dispersions suitable for use in a fundamental plane analysis. The data have a high signal-to-noise ratio (S/N) and the resulting random errors on the dispersions are very low, typically less that 5%. Uncertainties due to mismatch of the stellar templates have been minimized through several tests, and the total systematic error is of order similar to 5%. Good seeing enabled us to measure velocity dispersion profiles and rotation curves for most of the sample, and although a large fraction of the galaxies display a high level of rotation, the gradients of the total second moment of the kinematics are all very regular and similar to those in nearby galaxies. We conclude that the data therefore can be reliably corrected for aperture size in a manner consistent with nearby galaxy samples.