Cosmological constraints from evolution of cluster baryon mass function at z~0.5
Abstract
We present a new method for deriving cosmological constraints based on the evolution of the baryon mass function of galaxy clusters, and implement it using distant clusters from our 160deg2 ROSAT survey. The method takes advantage of direct and accurate Chandra measurements of the gas masses for distant clusters. It uses the cluster baryon mass as a proxy for the total mass, assuming only that their ratio is a universal quantity. We thereby avoid the uncertainties of the M_tot-T or M_tot-L_x relations used in all previous studies. We find strong evolution of the baryon mass function between z>0.4 and the present. The observed evolution defines a narrow band in the Omega-Lambda plane, Omega + 0.3 Lambda = 0.48 +- 0.08 at 68% confidence, which intersects with constraints from the Cosmic Microwave Background and supernovae Ia near Omega=0.3 and Lambda=0.7.Keywords
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