A search for X-ray bright distant clusters of galaxies

R. C. Nichol*, M. P. Ulmer, R. G. Kron, G. D. Wirth, D. C. Koo

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

9 Scopus citations


We present the results of a search for X-ray luminous distant clusters of galaxies. We found extended X-ray emission characteristic of a cluster toward two of our candidate clusters of galaxies. They both have a luminosity in the ROSAT bandpass of ≃ 1044 ergs s-1 and a redshift greater than 0.5; thus making them two of the most distant X-ray clusters ever observed. Furthermore, we show that both clusters are optically rich and have a known radio source associated with them. We compare our result with other recent searches for distant X-ray luminous clusters and present a lower limit of 1.2 × 10-7 Mpc-3 for the number density of such high-redshift clusters. This limit is consistent with the expected abundance of such clusters in a standard (b = 2) cold dark matter universe. Finally, our clusters provide important high-redshift targets for further study into the origin and evolution of massive clusters of galaxies.

Original languageEnglish (US)
Pages (from-to)464-468
Number of pages5
JournalAstrophysical Journal
Issue number2
StatePublished - Sep 10 1994


  • Galaxies: clusters of
  • X-rays: galaxies

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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