Abstract:
A complete census of supermassive black holes in the local universe is important, especially in low mass (log(stellar mass/solar masses) < 10) galaxies. It provides observational constraints on the black hole occupation fractions of low mass galaxies and broadens our understanding of the co-evolution of active galactic nuclei (AGN) and their host galaxies. Infrared selection criteria including [3.4]-[4.6] micron (W1-W2) color provides a useful method for detecting obscured AGN which may be missed in X-ray or optical surveys. Recent work has found that not only are there more AGN in low mass galaxies than would be predicted using optical selection criteria, but that the fraction of high W1-W2 (>0.5) galaxies is actually highest in the lowest mass galaxies. This could be evidence of a significant population of obscured AGN in low mass galaxies, but it is still unclear whether the dust heating that causes high W1-W2 color can only be caused by AGN or if stars alone are sufficient. This dissertation is a study of the demographics of high W1-W2 galaxies in the local universe and the AGN or star-forming nature of their nuclear activity.
