Abstract

The formation and evolution of massive galaxies in the first few billion years after the Big Bang remain important questions in extragalactic astronomy. Technological advancements allowing for multi-wavelength surveys that are both wide, covering large portions of the sky, and deep, pushing studies to higher redshifts, have opened the door for statistically significant studies of rare and important populations of galaxies at early times. Massive galaxies (with stellar mass Mstar > 1011 Msun) provide an excellent testbed for theoretical models of galaxy evolution, however, because they have low number densities, large area surveys are required in order to locate uniformly-selected, statistically significant samples of these objects. In this thesis I detail the methods used to locate the largest samples to date of these massive galaxies, I investigate their number densities, quenched fractions, and specific star-formation rates, and I perform detailed comparisons of my empirical results with predictions from theoretical models. This work is a significant advancement as it mitigates uncertainties from Poisson statistics and cosmic variance, effects which have historically limited studies of the massive galaxy population at cosmic noon.