The Chandra Deep Protocluster Survey: Point-source catalogues for a 400-ks observation of the z = 3.09 protocluster in SSA22

B. D. Lehmer, D. M. Alexander, S. C. Chapman, Ian Smail, F. E. Bauer, W. N. Brandt, J. E. Geach, Y. Matsuda, J. R. Mullaney, A. M. Swinbank

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57 Scopus citations


We present X-ray point-source catalogues for a deep ≈400-ks Chandra ACIS-I (Advanced CCD Imaging Spectrometer) exposure of the SSA22 field. The observations are centred on a z = 3.09 protocluster, which is populated by Lyman break galaxies (LBGs), Lyα emitters (LAEs) and extended Lyα-emitting blobs (LABs). The survey reaches ultimate (3 count) sensitivity limits of ≈5.7 × 10-17 and ≈3.0 × 10-16 erg cm-2 s-1 for the 0.5-2 and 2-8 keV bands, respectively (corresponding to L2-10 keV ≈5.7 × 1042 erg s-1 and L10-30 keV ≈2.0 × 1043 erg s-1 at z = 3.09, respectively, for an assumed photon index of Γ = 1.4). These limits make SSA22 the fourth deepest extragalactic Chandra survey yet conducted, and the only one focused on a known high-redshift structure. In total, we detect 297 X-ray point sources and identify one obvious bright extended X-ray source over a ≈330 arcmin 2 region. In addition to our X-ray catalogues, we provide all available optical spectroscopic redshifts and near-infrared and mid-infrared photometry available for our sources. The basic X-ray and infrared properties of our Chandra sources indicate a variety of source types, although absorbed active galactic nuclei (AGN) appear to dominate. In total, we have identified 12 X-ray sources (either via optical spectroscopic redshifts or LAE selection) at z = 3.06 - 3.12 that are likely to be associated with the SSA22 protocluster. These sources have X-ray and multiwavelength properties that suggest they are powered by AGN with 0.5-8 keV luminosities in the range of ≈10 43-1045 erg s-1. We have analysed the AGN fraction of sources in the protocluster as a function of local LAE source density and find suggestive evidence for a correlation between AGN fraction and local LAE source density (at the ≈96 per cent confidence level), implying that supermassive black hole growth at z ≈ 3 is strongest in the highest density regions.

Original languageEnglish (US)
Pages (from-to)299-316
Number of pages18
JournalMonthly Notices of the Royal Astronomical Society
Issue number1
StatePublished - Nov 2009

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


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