# X-ray surface brightness observations of galaxy clusters, cosmic opacity and the limits on the matter density parameter

## TL;DR

This study uses galaxy cluster X-ray data and H(z) measurements within a flat Lambda-CDM model to constrain cosmic opacity and find that current matter density estimates depend heavily on the universe's transparency, with results supporting a transparent universe.

## Contribution

It provides new constraints on cosmic opacity using galaxy cluster gas mass fractions combined with H(z) data, highlighting the dependence of matter density estimates on cosmic transparency assumptions.

## Key findings

- Current limits on matter density depend on cosmic transparency assumptions.
- Results are consistent with a transparent universe within 1 sigma confidence level.
- Supports previous findings of a transparent universe using multiple observational probes.

## Abstract

In this work, we use two gas mass fraction samples of galaxy clusters obtained from their X-ray surface brightness observations jointly with recent $H(z)$ data in a flat $\Lambda$CDM framework to impose limits on cosmic opacity. It is assumed that the galaxy clusters are in hydrostatic equilibrium and their gas mass fraction measurement is constant with redshift. We show that the current limits on the matter density parameter obtained from X-ray gas mass fraction test are strongly dependent on the cosmic transparency assumption even for a flat scenario. Our results are consistent with a transparent universe within $1\sigma$ c.l. in full agreement with other analyses which used type Ia supernovae, gamma ray burst and $H(z)$ data.