Date of Award
Honors Thesis (Open Access)
Colby College. Physics and Astronomy Dept.
Galaxy mergers are catastrophic events in that they greatly change the properties of the galaxies involved. Observations of the nearby universe suggest that they may also be able to trigger active galactic nuclei (AGN) even prior to the final coalescence, though there is much controversy surrounding this belief, particularly at high redshifts. In order to address this question, we have assembled a large sample of photometric galaxy pairs within the GDS and EGS fields of the CANDELS survey. We use photometric redshift probability distribution functions and the combined redshift probability function to assign probabilities for each projected pair. We incorporate pair probabilities into a survey of X-ray detected AGN to calculate weighted AGN fractions and AGN enhancements for interacting galaxies. Overall, for both major and minor mergers at 0.5 < z < 3.0, we find that AGN frequency is enhanced by 1.30 +/- 0.17, 1.54 +/- 0.24, and 3.21 +/- 0.72 in pairs separated by 20 < d < 30, 10 < d < 20, and d < 10 kpc respectively. We also separately investigate AGN enhancement in minor and major mergers and find that minor mergers might play a larger role than major mergers in triggering AGN at high redshifts. Finally, we investigate how redshift affects AGN enhancement in pairs, and we find no enhancement in galaxies at 1.5 < z < 3.0. However, more complete AGN surveys at high redshifts are required to confirm this trend.
Active galactic nuclei, Supermassive black holes, extragalactic, mergers
Recommended CitationDougherty, Sean L., "Investigating the AGN-Merger Connection Using Close Galaxy Pairs in the CANDELS Fields" (2021). Honors Theses. Paper 1328.