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Description
We present results from a {approx}100ks Chandra observation of the 2QZ Cluster 1004+00 structure at z=2.23 (hereafter 2QZ Clus). 2QZ Clus was originally identified as an overdensity of four optically-selected QSOs at z=2.23 within a 15x15arcmin^2^ region. Narrow-band imaging in the near-IR (within the K band) revealed that the structure contains an additional overdensity of 22 z=2.23 H{alpha}-emitting galaxies (HAEs), resulting in 23 unique z=2.23 HAEs/QSOs (22 within the Chandra field of view). Our Chandra observations reveal that three HAEs in addition to the four QSOs harbor powerfully accreting supermassive black holes (SMBHs), with 2-10keV luminosities of ~(8-60)x10^43^erg/s and X-ray spectral slopes consistent with unobscured active galactic nucleus (AGN). Using a large comparison sample of 210 z=2.23 HAEs in the Chandra-COSMOS field (C-COSMOS), we find suggestive evidence that the AGN fraction increases with local HAE galaxy density. The 2QZ Clus HAEs reside in a moderately overdense environment (a factor of {approx}2 times over the field), and after excluding optically-selected QSOs, we find that the AGN fraction is a factor of {approx}3.5^+3.8^_-2.2_ times higher than C-COSMOS HAEs in similar environments. Using stacking analyses of the Chandra data and Herschel SPIRE observations at 250{mu}m, we respectively estimate mean SMBH accretion rates ((dM/dt)_BH_) and star formation rates (SFRs) for the 2QZ Clus and C-COSMOS samples.
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