2002MNRAS.330..631E

The X-ray luminosities of the Einstein Extended Medium Sensitivity Survey (EMSS) clusters of galaxies with redshifts (formula) are remeasured using ROSAT Position Sensitive Proportional Counter (PSPC) data. It is found that the new luminosities are on average (formula) 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 (formula) times the previous measurements. The X-ray luminosity function (XLF) at (formula) is recalculated and is found to be consistent with the local XLF. The constraints on the updated properties of the (formula) 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 (formula). The implications of this result are discussed in terms of constraints on the cosmological parameter Ω₀