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Title: The cosmological evolution of radio sources
Author: Brookes, Mairi Halliday
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2007
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This thesis presents extensive follow-up observations of the Combined EIS-NVSS survey Of Radio Sources (CENSORS) with the primary scientific goal of studying the high redshift behaviour of the radio luminosity function. Understanding the behaviour of radio galaxies and quasars at these high redshifts is of far-reaching importance. Massive black holes reside in all present day galaxies with mass roughly proportional to the mass of the bulge of the galaxy. This suggests that black hole and spheroid formation are intimately linked. Radio loud emission from active galaxies only occurs in association with the most massive black holes. So by studying the cosmic evolution of radio sources we are also studying the cosmic evolution of the upper end of the black hole mass function which has relevance to the formation of massive galaxies at high redshift. Previous studies of radio galaxies at redshifts greater than 2 have failed to agree on the presence or absence of a cut-off in commoving number density. CENSORS is a 1.4GHz survey compete to a flux limit of 7.2mJy in which sources were selected on the basis of their flux and coincidence with the ESO Imaging Survey Wide Patch D (a 3 by 2 degree field at RA: 09 51 00 and DEC: -21 00 00). Initial identification of host galaxies was performed by comparison of the optical EIS imaging and the radio observations from the 1.4Ghz follow up observations with the Very Large Array. Following this preparatory work, this thesis presents K-band imaging of those host galaxies not detected (or only marginally detected) in I-band EIS images, and optical spectroscopy which brings the sample to 65% spectroscopic completeness. For those sources for which a spectroscopic redshift could not be identified, photometric redshift estimates are made. These data are then used as part of the constraint for a model of the variation of the radio luminosity function with redshift. A 200 parameter grid in radio luminosity and redshift is fitted to the redshift distribution of CENSORS and other radio surveys; the 1.4GHz source counts and the local radio luminosity function.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available