Internal Kinematics of Spiral Galaxies in Distant Clusters

We introduce our project on galaxy evolution in the environment of rich clusters, aiming at disentangling the importance of specific interaction and galaxy transformation processes from the hierarchical evolution of galaxies in the field. Emphasis is laid on the examination of the internal kinematics of disk galaxies through spatially resolved multiobject spectroscopy with FORS at the Very Large Telescope. First results are presented for the clusters MS 1008.1-1224 (z = 0.30), Cl 0303+1706 (z = 0.42), and Cl 0413-6559 (F1557.19TC; z = 0.51). Out of 30 cluster members with emission lines, 13 galaxies exhibit a rotation curve of the universal form rising in the inner region and passing over into a flat part. The other members have either intrinsically peculiar kinematics (4), too strong geometric distortions (9), or a too low signal-to-noise ratio (4) for a reliable classification of their velocity profiles. The 13 cluster galaxies for which a maximum rotation velocity could be derived are distributed in the Tully-Fisher diagram very similar to field galaxies from the FORS Deep Field that have corresponding redshifts and do not show any significant luminosity evolution with respect to local samples. The same is true for the seven galaxies observed in the cluster fields that turned out not to be members. The mass-to-light ratios of the 13 Tully-Fisher cluster spiral galaxies cover the same range as the distant field population, indicating that their stellar populations were not dramatically changed by possible cluster-specific interaction phenomena. The cluster members with distorted kinematics may be subject to interaction processes, but it is impossible to determine whether or not these processes also lead to changes in the overall luminosity of their stellar populations.