The Chandra Deep Field North survey. IX. Extended X-ray sources

F. E. Bauer, D. M. Alexander, W. N. Brandt, A. E. Hornschemeier, T. Miyaji, G. P. Garmire, D. P. Schneider, M. W. Bautz, G. Chartas, R. E. Griffiths, W. L.W. Sargent

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58 Scopus citations


The ≈1 Ms Chandra Deep Field North observation is used to study the extended X-ray sources in the region surrounding the Hubble Deep Field North (HDF-N), yielding the most sensitive probe of extended X-ray emission at cosmological distances to date. A total of six such sources are detected, the majority of which align with small numbers of optically bright galaxies. Their angular sizes, band ratios, and X-ray luminosities-assuming they lie at the same distances as the galaxies coincident with the X-ray emission - are generally consistent with the properties found for nearby groups of galaxies. One source is notably different and is likely to be a poor-to-moderate X-ray cluster at high redshift (i.e., z ≳ 0.7). This source has a large angular extent, a double-peaked X-ray morphology, and an overdensity of unusual objects [very red objects, optically faint (I ≥ 24) radio and X-ray sources]. Another of the six sources is coincident with several z ≈ 1.01 galaxies located within the HDF-N itself, including the FR I radio galaxy VLA J123644+621133, and is likely to be a group or poor cluster of galaxies at that redshift. We are also able to place strong constraints on the optically detected cluster of galaxies ClG 1236+6215 at z = 0.85 and the wide-angle-tailed radio galaxy VLA J123725+621128 at z ∼ 1-2; both sources are expected to have considerable associated diffuse X-ray emission, and yet they have rest-frame 0.5-2.0 keV X-ray luminosities of ≲3 × 10 42and ≲(3-15) × 1042 ergs s-1, respectively. The environments of both sources are either likely to have a significant deficit of hot intracluster gas compared with local clusters of galaxies, or they are X-ray groups. We find the surface density of extended X-ray sources in this observation to be 167-67+97 deg -2 at a limiting soft-band flux of ≈3 × 10-16 ergs cm-2 s-1. No evolution in the X-ray luminosity function of clusters is needed to explain this value.

Original languageEnglish (US)
Pages (from-to)1163-1178
Number of pages16
JournalAstronomical Journal
Issue number3 1755
StatePublished - Mar 2002

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


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