# A Spectroscopic Census of X-ray Systems in the COSMOS Field

## TL;DR

This study provides a detailed spectroscopic analysis of X-ray detected galaxy systems in the COSMOS field, revealing their properties and scaling relations, and addressing challenges in low-luminosity system identification.

## Contribution

It offers the first comprehensive spectroscopic census of X-ray systems in COSMOS, including new measurements and analysis of their scaling relations and morphological complexities.

## Key findings

- X-ray systems' $L_{X}$-$\sigma_{v}$ relation aligns with massive clusters.
- Identified 137 groups with >3 members and 1843 member candidates.
- Challenges in low-luminosity system classification due to complex morphologies.

## Abstract

We investigate spectroscopic properties of galaxy systems identified based on deep X-ray observations in the COSMOS field. The COSMOS X-ray system catalog we use George et al. (2011) includes 180 X-ray systems to a limiting flux of $1.0 \times 10^{-15}$ erg cm$^{-2}$ s$^{-1}$, an order of magnitude deeper than future e-ROSITA survey. We identify spectroscopic members of these X-ray systems based on the spectroscopic catalog constructed by compiling various spectroscopic surveys including 277 new measurements; 137 X-ray systems are spectroscopically identified groups with more than three spectroscopic members. We identify 1843 spectroscopic redshifts of member candidates in these X-ray systems. The X-ray luminosity ($L_{X}$) - velocity dispersion ($\sigma_{v}$) scaling relation of the COSMOS X-ray systems is consistent with that of massive X-ray clusters. One of the distinctive features of the COSMOS survey is that it covers the X-ray luminosity range where poor groups overlap the range for extended emission associated with individual quiescent galaxies. We assess the challenges posed by the complex morphology of the distribution of low X-ray luminosity systems, including groups and individual quiescent galaxies, in the $L_{x} - \sigma_{v}$ plane.