Abstract
The gas mass fraction in galaxy clusters is a convenient tool to use in the context of cosmological studies. Indeed this quantity allows to constrain the universal baryon fraction Ωb/Ωm, as well as other parameters like the matter density Ωm, the Hubble parameter h or the Equation of State of Dark Energy w. This gas mass fraction is also sensitive to baryonic effects that need to be taken into account, and that translate into nuisance parameters. Two of them are the depletion factor ϒ, and the hydrostatic mass bias B = (1 - b). The first one describes how baryons are depleted in clusters with respect to the universal baryon fraction, while the other encodes the bias coming from the fact that the mass is deduced from X-ray observations under the hypothesis of hydrostatic equilibrium. We will show preliminary results, obtained using the Planck-ESZ clusters observed by XMM-Newton, on both cosmological and cluster parameters. We will notably discuss the investigation on a possible redshift dependence of the mass bias, which is considered to be non-existent in hydrodynamic simulations based on Λ-CDM, and compare our results with other studies.
Highlights
Being the most massive gravitationally bound systems of our universe, galaxy clusters carry a lot of information
Their baryonic component being mainly under the form of hot gas [2], of which the fraction is assumed to be relatively well known and understood, the gas mass fraction of galaxy clusters can be used as a robust cosmological probe
Clusters being the siege of astrophysical phenomena, the gas mass fraction is sensitive to the baryonic physics inside these objects
Summary
Being the most massive gravitationally bound systems of our universe, galaxy clusters carry a lot of information They can notably be used as powerful cosmological probes [1], or as astrophysical objects of study, to better understand the physics of the intra-cluster medium. Their baryonic component being mainly under the form of hot gas [2], of which the fraction is assumed to be relatively well known and understood, the gas mass fraction of galaxy clusters can be used as a robust cosmological probe
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