The baryon fraction in X-Rays galaxy clusters revisited

• Main Authors: Sadat, R., Blanchard, A., Douspis, M.
• Format: Report
• Language: unknown
• Published: arXiv 2001
• Subjects: Astrophysics astro-ph; FOS Physical sciences; Blanchard; Rovaniemi
• Online Access: https://dx.doi.org/10.48550/arxiv.astro-ph/0112105; https://arxiv.org/abs/astro-ph/0112105

One of the most direct way to constrain the matter density of the universe $Ω_M$ is to measure the baryon content in X-Rays clusters of galaxies. Typical value of the mean gas mass fraction is $\fg \sim 0.15h^{-3/2}$ which leads to $\omM <0.4$. In this talk I will discuss the issue of the gas fraction radial distribution inside a cluster and foccus on the apparent discrepancy between the theoretical shape predicted by numerical simulations and the observations. I will show that a significant part of this discrepancy is due to several systematics in both the gas mass and total mass determinations. Revising the gas as well as the binding masses removes such a discrepancy and results in a lower baryon mass fraction of $\fb(r_{500}) \sim 10 %$ (Sadat & Blanchard 2001). Finally, I will discuss the cosmological constraints we obtain when we combine the revised baryon fraction with primordial fluctuations. : 9 pages, 5 figures, talk given at COSMO-01 Workshop, Rovaniemi, Finland, August 30 - September 4, 2001 Slight revision to Fig. 3 caption