Galaxy kinematics in the XMM2235 cluster field at z~1.4

We took spatially resolved slit FORS2 spectra of 19 cluster galaxies at z=1.4, and 8 additional field galaxies at 1u003czu003c1.2 using the ESO Very Large Telescope. The targets were selected from previous spectroscopic and photometric campaigns. Our spectroscopy was complemented with HST-ACS imaging in the F775W and F850LP filters mandatory for deriving the galaxy structural parameters accurately. We analyzed the ionized gas kinematics by extracting rotation curves from the two-dimensional spectra. Taking into account all geometrical, observational, and instrumental effects, these rotation curves were used to derive the intrinsic maximum rotation velocity (Vmax). Vmax was robustly determined for 6 cluster galaxies and 3 field galaxies. Galaxies with sky contamination or insufficient spatial rotation curve extent were not included in our analysis. We compared our sample to the local B-band Tully-Fisher relation (TFR) and the local Velocity-Size relation (VSR) finding that cluster galaxies are on average 1.7 mags brighter and a factor 2 smaller. Cluster galaxies can be divided into two subsamples by the locii they occupy in the Tully-Fisher diagram, with half of the members each. For the high-mass sample the average deviation from the local B-band TFR is -0.7 mags. This mild evolution may be driven by younger stellar populations (SP) of distant galaxies with respect to their local counterparts, and thus, an increasing luminosity is expected towards higher redshifts. However, the low-mass group consist of 3 highly overluminous galaxies with average B-band TF offsets of -2.5 mags. This deviation can no longer be explained by the gradual evolution of SP with lookback time and thus, we suspect that we see rather compact galaxies that got an enhancement of star formation during their infall towards the dense regions of the cluster due to interactions with the intracluster medium.