Galaxy Evolution: The DRaGONS Survey and Luminosity Functions With Photometric Redshifts

This thesis examines two complementary approaches to the study of galaxy evolution using multiwavelength large area galaxy surveys. The first part of the thesis focuses on a statistical study of the overall galaxy population, namely the evolution of galaxy luminosity functions, while the second part of the thesis aims to study an interesting population of rare galaxies selected based on their radio and optical properties, namely high redshift radio galaxies selected from SDSS and FIRST. We compute the luminosity function (LF) for the general galaxy population and as a function of type using photometric redshifts derived from the SDSS Southern Survey. We present a new maximum likelihood estimator and show that it accounts for the uncertainties associated with photometric redshifts. In addition to three existing parameterizations, we introduce the use of cubic BSplines to fit the luminosity function. We show evidence for the evolution of the luminosity function, but defer much of the analysis until a better photometric redshift dataset is available. The second part of the thesis describes the Distant Radio Galaxies Optically Non- detected in SDSS (DRaGONS) survey. Our new selection criteria appear to be very efficient at identifying high redshift radio galaxies, including a substantial population of shallow spectrum radio sources missed by competing selection techniques. These sources, when confirmed, will have a dramatic effect on the empirical z-alpha relation. I describe the environment of early galaxy formation through the study of nearby Extremely Red Objects (EROs) and faint K-band galaxy counts. We find an excess number of faint EROs and galaxies around a subset of DRaGONS candidates, indicating that massive galaxies form in overdense environments. 10% of DRaGONS galaxies are redder than expected, which indicates moderate obscuration and the possible presence of ongoing star formation. These objects, which we dub Red DRaGONS, could represent a significant radio-loud population missing from optically selected AGN surveys