A reanalysis of the X-ray luminosities of clusters of galaxies with 0.3<z <0.6 in the EMSS sample

The X-ray luminosities of the Einstein Extended Medium Sensitivity Survey (EMSS) clusters of galaxies with redshifts 0.3<z<0.6 are remeasured using ROSAT Position Sensitive Proportional Counter (PSPC) data. It is found that the new luminosities are on average 1.18+/-0.08 times higher than previously measured, but also that this ratio depends strongly on the X-ray core radii we measure. For the clusters with small core radii, in general we confirm the EMSS luminosities, but for clusters with core radii >250kpc (the constant value assumed in the EMSS), the new luminosities are 2.2+/-0.15 times the previous measurements. The X-ray luminosity function (XLF) at 0.3<z<0.6 is recalculated and is found to be consistent with the local XLF. The constraints on the updated properties of the 0.3<z<0.6 EMSS sample, including a comparison with the number of clusters predicted from local XLFs, indicate that the space density of luminous, massive clusters either has not evolved or has increased by a small factor ~2 since z=0.4. The implications of this result are discussed in terms of constraints on the cosmological parameter Ω₀.