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

Abstract

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. © 2009 RAS.