Cosmological constraints on Chaplygin gas dark energy from galaxy cluster x-ray and supernova data

Abstract

The recent observational evidence for the present accelerated stage of the Universe has stimulated renewed interest in alternative cosmologies. In general, such models contain an unknown negative-pressure dark component that explains the supernova results and reconciles the inflationary flatness prediction $({\ensuremath{\Omega}}_{T}=1)$ and the cosmic microwave background measurements with the dynamical estimates of the quantity of matter in the Universe $({\ensuremath{\Omega}}_{m}\ensuremath{\simeq}0.3\ifmmode\pm\else\textpm\fi{}0.1).$ In this paper we study some observational consequences of a dark energy candidate, the so-called generalized Chaplygin gas, which is characterized by an equation of state ${p}_{C}=\ensuremath{-}A/{\ensuremath{\rho}}_{C}^{\ensuremath{\alpha}},$ where A and $\ensuremath{\alpha}$ are positive constants. We investigate the prospects for constraining the equation of state of this dark energy component by combining Chandra observations of the x-ray luminosity of galaxy clusters, independent measurements of the baryonic matter density, the latest measurements of the Hubble parameter as given by the HST Key Project, and data of the Supernova Cosmology Project. We show that very stringent constraints on the model parameters can be obtained from this combination of observational data.