The correlation function of flux-limited X-ray clusters

Neta A. Bahcall, Renyue Cen

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7 Scopus citations


We show that the spatial correlation function of a flux-limited sample of X-ray-selected clusters of galaxies will exhibit a correlation scale that is smaller than the correlation scale of a volume-limited, richness-limited sample of comparable apparent spatial density. The flux-limited sample contains clusters of different richnesses at different distances: poor groups are found nearby and rich clusters at greater distances. Since the cluster correlation strength is known to increase with richness, the flux-limited sample averages over the correlations of poor and rich clusters. On the other hand, a volume-limited, richness-limited sample has a minimum richness threshold, and a constant mixture of richnesses with redshift. Using the observed correlation scale for rich (R ≥ 1) clusters, r0(R ≥ 1) = 21 ± 2 h-1 Mpc, that was determined from previous volume-limited studies, we derive for the ROSAT flux-limited X-ray cluster sample r0 (flux-limited) ≈ 14 h-1 Mpc, in agreement with the recently observed value of 13.7 ± 2.3 h-1 Mpc.

Original languageEnglish (US)
Pages (from-to)L15-L18
JournalAstrophysical Journal
Issue number1 PART 2
StatePublished - May 1 1994

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • Cosmology: large-scale structure of universe
  • Galaxies: clusters of
  • X-rays: galaxies


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