ChaMP serendipitous galaxy cluster survey

W. A. Barkhouse, P. J. Green, A. Vikhlinin, D. W. Kim, D. Perley, R. Cameron, J. Silverman, A. Mossman, R. Burenin, B. T. Jannuzi, M. Kim, M. G. Smith, R. C. Smith, H. Tananbaum, B. J. Wilkes

Research output: Contribution to journalArticlepeer-review

49 Scopus citations


We present a survey of serendipitous extended X-ray sources and optical cluster candidates from the Chandra Multiwavelength Project (ChaMP). Our main goal is to make an unbiased comparison of X-ray and optical cluster detection methods. In 130 archival Chandra pointings covering 13 deg2, we use a wavelet decomposition technique to detect 55 extended sources, of which 6 are nearby single galaxies. Our X-ray cluster catalog reaches a typical flux limit of about ∼10-14 ergs cm-2 s-1, with a median cluster core radius of 21′. For 56 of the 130 X-ray fields, we use the ChaMP's deep NOAO 4 m MOSAIC g′, r′, and i′ imaging to independently detect cluster candidates using a Voronoi tessellation and percolation (VTP) method. Red-sequence filtering decreases the galaxy fore- and background contamination and provides photometric redshifts to z ∼ 0.7. From the overlapping 6.1 deg2 X-ray/optical imaging, we find 115 optical clusters (of which 11% are in the X-ray catalog) and 28 X-ray clusters (of which 46% are in the optical VTP catalog). The median redshift of the 13 X-ray/optical clusters is 0.41, and their median X-ray luminosity (0.5-2 keV) is LX = (2.65 ± 0.19) × 1043 ergs s -1. The clusters in our sample that are only detected in our optical data are poorer on average (∼4 σ) than the X-ray/optically matched clusters, which may partially explain the difference in the detection fractions.

Original languageEnglish (US)
Pages (from-to)955-976
Number of pages22
JournalAstrophysical Journal
Issue number2 I
StatePublished - Jul 10 2006


  • Galaxies: clusters: general
  • Surveys
  • X-rays: galaxies: clusters

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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