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

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.