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The Co-Evolution of Black Holes and Galaxies.

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Title:The Co-Evolution of Black Holes and Galaxies.
Authors:Suh, Hyewon
Contributors:Astronomy (department)
Date Issued:Aug 2017
Publisher:University of Hawaiʻi at Mānoa
Abstract:The growth of black holes appears to be closely connected with galaxy evolution, and yet
how nuclear activity affects the growth of their host galaxies remains unclear. The main
focus of this dissertation research is to systematically study the influence of nuclear activity
on the growth of galaxies by examining the possible connection between AGN activity and
star formation. By combining multi-wavelength photometry and spectroscopy, I characterize
the properties of one of the largest samples of X-ray AGNs and their host galaxies up to
z ∼ 3. To quantify the growth rate of black holes, I determine black hole masses (MBH) and
Eddington ratios via the virial method using optical and near-IR spectroscopic observations.
To derive AGN host galaxy properties, I develop a multi-component SED fitting technique
which allows to disentangle the nuclear emission from the stellar light, and derive reliable
physical properties, such as stellar masses (Mstellar) and star formation rates (SFRs).
AGN host galaxies have, on average, SFRs that are consistent with those expected
from normal star-forming galaxies with similar Mstellar and redshift ranges, suggesting no
clear evidence for enhanced or suppressed star formation. Furthermore, the MBH −Mstellar
distribution for the majority of AGN host galaxies beyond the local universe is broadly
consistent with the correlation that we observe today, indicating no significant evolution
in the MBH − Mstellar relation. These results are in agreement with the observed lack
of correlation between SFRs and AGN accretion, which can be explained by the AGN
variability along with the broadly distributed Eddington ratios. I conclude that secular
evolution may play an important role in growing both black holes and galaxies hosting
moderate-luminosity AGNs at later cosmic time (z < 3).
Description:Ph.D. Thesis. University of Hawaiʻi at Mānoa 2017.
Rights:All UHM dissertations and theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission from the copyright owner.
Appears in Collections: Ph.D. - Astronomy

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