Dark Galaxies in the A1367 Galaxy Cluster

TL;DR

This study identifies and characterizes optically dark, X-ray bright galaxy-like sources in the A1367 cluster, suggesting they form through stripping and heating processes affecting galaxy evolution.

Contribution

It reports the discovery and detailed analysis of dark galaxies in A1367, highlighting their properties and formation mechanism, which was not previously documented.

Findings

Detected extended X-ray sources without optical counterparts.

These sources have galaxy-like sizes and specific mass and temperature ranges.

The X-ray emission is thermal with low metallicity, indicating a stripping and heating origin.

Abstract

We have characterized a sample of extended X-ray sources in the A1367 galaxy cluster that lack optical counterparts. The sources are galaxy size and have an average total mass of $1.3\times10^{11}$ solar masses. The average hot gas mass is $3.0\times10^{9}$ solar masses and the average X-ray luminosity is $4.3\times10^{41}$ erg cm$^{-2}$ s$^{-1}$. Analysis of a composite source spectrum indicates the X-ray emission is thermal, with temperature of 1.25 - 1.45 keV and has low metallicity, 0.026 - 0.067 solar. The average hot gas radius (12.7 kpc) is well matched to nominal stripping radius. We argue that this optically dark, X-ray bright galaxy population forms by a sequence of stripping followed by heating and mixing with the intracluster medium.