Morpho-kinematics of MACS J0416.1-2403 low mass galaxies

Abstract: We use optical spectroscopy from VLT/MUSE, as well as photometric observations from HST and VLT/HAWK-I, to study the morpho-kinematics of 17 low mass MACS J0416.1-2403 cluster galaxies at R200 and 5 field galaxies with a redshift of z~0.4. By measuring fluxes of emission lines, we have recovered the star formation rates, gas-phase metallicities and the spatially resolved gas kinematics. We have analysed the structure and morphology of the galaxies from the photometric data, performing a multi-component decomposition into a bulge and a disk. The spatially resolved gas velocity fields were modelled using a 3D approach, which allowed us to retrieve their intrinsic gas kinematics, including the maximum rotation velocity and velocity dispersion. The cluster and field population can be classified as star forming main-sequence galaxies, with only a sub-sample of 4 quenched systems. The lowest mass systems deviate from the predictions of the fundamental metallicity relation, showing higher metallicities, whereas the higher mass ones are in accordance with the model predictions. This might hint at the cut-off of pristine gas inflow and/or the removal of the hot halo gas as the mechanisms driving these offsets. Our morpho-kinematic analysis reveals a sub-sample of dwarfs with maximum velocities vmax <50 km/s, which depart from the Tully-Fisher relation. This might indicate that their interstellar medium is affected by ram pressure stripping. However, ~30% of the cluster galaxies have rotation-dominated gas disks and follow the Tully-Fisher relation. In the stellar mass-S0.5 plane, the systems follow a tight sequence, with only a sub-population of 5 galaxies strongly departing from this relation. Both the morphology and kinematics of the outlier galaxies hint at a combination of pre-processing and cluster-specific interactions affecting their stellar and gas disks.