# Kinematics of disk galaxies in (proto-)clusters at z=1.5

## TL;DR

This study investigates the kinematic properties of star-forming galaxies in (proto-)clusters at z=1.5, revealing their luminosity, dynamical state, and interaction effects through integral field spectroscopy.

## Contribution

It provides the first detailed kinematic analysis of (proto-)cluster galaxies at z=1.5 using Halpha spectroscopy, highlighting differences from field galaxies and insights into cluster environment effects.

## Key findings

- Galaxies are more luminous than local counterparts of similar mass.
- Kinematic asymmetries are higher in (proto-)cluster galaxies compared to present-day clusters.
- Vmax/sigma_g ratios indicate less settled disks at z=1.5.

## Abstract

We observed star-forming galaxies at z~1.5 selected from the HyperSuprimeCam Subaru Strategic Program. The galaxies are part of two significant overdensities of [OII] emitters identified via narrow-band imaging and photometric redshifts from grizy photometry. We used VLT/KMOS to carry out Halpha integral field spectroscopy of 46 galaxies in total. Ionized gas maps, star formation rates and velocity fields were derived from the Halpha emission line. We quantified morphological and kinematical asymmetries to test for potential gravitational (e.g. galaxy-galaxy) or hydrodynamical (e.g. ram-pressure) interactions. Halpha emission was detected in 36 targets. 34 of the galaxies are members of two (proto-)clusters at z=1.47, confirming our selection strategy to be highly efficient. By fitting model velocity fields to the observed ones, we determined the intrinsic maximum rotation velocity Vmax of 14 galaxies. Utilizing the luminosity-velocity (Tully-Fisher) relation, we find that these galaxies are more luminous than their local counterparts of similar mass by up to ~4 mag in the rest-frame B-band. In contrast to field galaxies at z<1, the offsets of the z~1.5 (proto-)cluster galaxies from the local Tully-Fisher relation are not correlated with their star formation rates but with the ratio between Vmax and gas velocity dispersion sigma_g. This probably reflects that, as is observed in the field at similar redshifts, fewer disks have settled to purely rotational kinematics and high Vmax/sigma_g ratios. Due to relatively low galaxy velocity dispersions (sigma_v < 400 km/s) of the (proto-)clusters, gravitational interactions likely are more efficient, resulting in higher kinematical asymmetries, than in present-day clusters. (abbr.)