The X-Ray Luminosity Function of Nearby Rich and Poor Clusters of Galaxies:A Cosmological Probe

In this letter, we present a new determination of the local (z<0.09) X-rayluminosity function (XLF) using a large, statistical sample of 294 Abellclusters and the ROSAT All-Sky-Survey. Given our large sample size, we havereduced errors by a factor of two for L(X)(0.5-2keV)>10^43 ergs/sec. We combineour data with previous work in order to explore possible constraints imposed bythe shape of the XLF on cosmological models. A set of currently viablecosmologies is used to construct theoretical XLFs assuming Lx is proportionalto M^p and a sigma_8-Omega_0 constraint (from Viana & Liddle 1996) based on thelocal X-ray temperature function. We fit these models to our observed XLF andverify that the simplest adiabatic, analytic scaling relation (e.g. Kaiser1986) disagrees strongly with observations. If we assume that clusters can bedescribed by the pre-heated, constant core-entropy models of Evrard & Henry(1991) then the observed XLF is consistent only with 0.1 < Omega_0 < 0.4 if theenergy per unit mass in galaxies is roughly equal to the gas energy (ie ifbeta=1). (abridged)Comment: 4 pages, 2 figures, accepted for publication in ApJ Letters. uses emulateapj.st