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Title: X-ray surveys of active galactic nuclei in field and cluster environments
Author: Johnson, Olivia
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2004
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In recent years, the Chandra and XMM-Newton observatories have allowed the AGN generating the majority of the accretion power in the Universe to be observed for the first time. In this thesis, I present three X-ray surveys designed to characterize the AGN populations within the varied environments of a dense galaxy cluster, a forming protocluster, and the field. I survey the AGN content of the z = 0.83 galaxy cluster MS1054-03 based on archival Chandra data. I detect 47 X-ray point sources in the MS1054-03 field, of which two are confirmed from pre-existing spectroscopy to be luminous AGN at the redshift of the cluster. At bright fluxes, I find a 2σ excess of point sources compared to predictions from field surveys, consistent with ~ 6 additional clusters AGN. Combined with the identification of 7 cluster AGN in deep radio observations, these observations suggest significantly enhanced AGN activity in MS1054-03 compared to local galaxy clusters. The excess of X-ray detected AGN is found at radial distances of 1 to 2 Mpc from the cluster centre, suggesting they may be associated with infalling galaxies. The radio AGN are seen within the inner Mpc of the cluster and are largely undetected in the X-ray, suggesting they are either intrinsically less luminous and/or heavily obscured. I present X-ray and optical observations of the SSA22 protocluster region at z = 3.09. Almost certainly the precursor to a bright X-ray cluster, this galaxy overdensity comprises ~ 160 galaxies within a region of 10 by 14 comoving Mpc including Ly-break galaxies, Ly-alpha galaxies, SCUBA galaxies, and two large extended sources of diffuse Lyα emission. I have supplemented the known catalog of objects associated with the protocluster by analyzing a wide-field narrow-band Lyα observation in which ~ 40 additional z = 3.09 candidates are identified. In an extremely deep (150 ks) XMM-Newton observation of this field, I find no evidence for diffuse X-ray emission associated with either a hot intracluster medium or the diffuse Lyα flux. While none of the SCUBA sources in the field have X-ray counterparts, and the direct detection rate for Ly-break and Lyα galaxies in the structure is low. I put limits on the X-ray emission from the sources comprising the protocluster by performing an X-ray stacking analysis of the various high redshift populations. Finally, I discuss work done in support of the ELAIS Deep X-ray Survey (EDXS), an early Chandra ‘blank field’ survey designed to characterize the components of the XRB and to study their relation to populations detected in other wavebands.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available