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

S. C. Ellis*, L. R. Jones

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

10 Citations (Scopus)


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 >250 kpc (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.

Original languageEnglish
Pages (from-to)631-641
Number of pages11
JournalMonthly Notices of the Royal Astronomical Society
Issue number3
Publication statusPublished - 1 Mar 2002
Externally publishedYes


  • Cosmology: observations
  • Galaxies: clusters: general
  • X-rays: galaxies


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