# A spectroscopic study of a rich cluster at z=1.52 with Subaru $\&$ LBT: the environmental impacts on the mass-metallicity relation

## TL;DR

This study uses near-infrared spectroscopy to confirm a galaxy cluster at z=1.52 and investigates how the environment influences the mass-metallicity relation, finding minimal environmental impact at this redshift.

## Contribution

First spectroscopic confirmation of a z=1.52 galaxy cluster and analysis of its environment's effect on the mass-metallicity relation at high redshift.

## Key findings

- The cluster is gravitationally bound with possible filamentary structures.
- The mass-metallicity relation in the cluster matches that of field galaxies at similar redshifts.
- Environmental impact on the mass-metallicity relation appears small at z=1.52.

## Abstract

We present the results of our near-infrared (NIR) spectroscopic observations of a rich cluster candidate around a radio galaxy at $z=1.52$ (4C65.22) with Subaru/MOIRCS and LBT/LUCI. We observed 71 galaxies mostly on the star-forming main sequence selected by our previous broad-band (photo-$z$) and narrow-band H$\alpha$ imaging observation in this cluster environment. We successfully confirmed the redshifts of 39 galaxies, and conclude that this is a gravitationally bound, real cluster at $z=1.517$. Our spectroscopic data also suggest a hint of large-scale filaments or sheet-like three-dimensional structures crossing at the highest-density cluster core. By stacking the spectra to derive their average interstellar medium (ISM) gas-phase metallicity based on the [NII]/H$\alpha$ emission line flux ratio, we find that the mass-metallicity relation (MZR) in the 4C65.22 cluster environment is consistent with that of H$\alpha$-selected field galaxies at similar redshifts. Our results suggest that the environmental impacts on the MZR is small at high redshifts, but a larger sample of high-$z$ clusters and their member galaxies is still required to fully address the effect of environment as well as its cluster-cluster variation.