I will present results from the recently completed GOODS NICMOS Survey, which utilizes 180 orbits of the HST with NIC-3 H-band imaging of >8000 galaxies in the GOODS fields. We construct a unique sample of 80 extremely massive galaxies (with log(M*) > 11) at high redshifts (z = 1.7 - 3) and examine their merger properties through morphological and close pair methods. This represents the largest and most thorough merger history examination to date for massive galaxies at high redshifts. We conclude that these galaxies will experience on average 4 - 5 mergers with companion galaxies greater than log(M*) = 9, leading to a stellar mass increase of a factor of three from z = 3 to the present. We present arguments that this merging can explain most of the observed size evolution, of up to a factor of five in effective radii,  over the same epoch of cosmic history. 

We also examine the AGN sub-sample of these galaxies, concluding that at least one third of all massive galaxies will go through a Seyfert luminosity (or brighter) AGN phase leading to an average massive galaxy releasing through its AGN at least 35 times its binding energy in radiation throughout its lifetime. We observe no strong evolution in the local black hole mass - galaxy stellar mass relation, suggesting that supermassive black holes and their hosts grow principally together over the history of the Universe. We also note that it is massive galaxy Seyferts which dominate the X-ray luminosity function at all redshifts, up to z = 3. The profound implications of these processes will be discussed in relation to massive galaxy formation and evolution. 

This work was funded by the STFC, the Leverhulme Trust, and NASA/STSci grant HST-GO11082. I also gratefully acknowledge support from Gemini Observatory to carry out this research.