G5 Article dissertation

Galaxy evolution through the lens of active galactic nuclei, their host galaxies, and environments




AuthorsStone Maria Babakhanyan

PublisherTurun yliopisto

Publishing placeTurku

Publication year2024

ISBN978-951-29-9720-6

eISBN 978-951-29-9721-3

Web address https://urn.fi/URN:ISBN:978-951-29-9721-3


Abstract

The body of research relayed in this dissertation pertains to investigating the immediate environments of Type I quasars for clues to the formation and evolution of galaxies through observations. The neighboring galaxies are key agents in the local environment around the quasar. Through longslit (Paper I) and multi-object spectroscopy (Paper II), I contributed to the identification of neighboring galaxies within several hundred kiloparsec projected distance of 44 low redshift quasars from the Falomo et al. (2014) catalog of 416 quasars located in the Stripe82 region of the Sloan Digital Sky Survey (SDSS). I found that the quasars and inactive galaxies had a similar number of companion galaxies at low redshifts and that the quasar companions had a moderate star formation rate. In papers III and IV, I was able to tap into the rich archival data from the Galaxy and Mass Assembly (GAMA) spectroscopic survey to investigate quasar environments at low redshifts using larger statistics (more than 200 quasars). I studied the properties of the bright neighbors within a close volume centered on a quasar and looked at the host galaxy star formation histories. I found that the properties of spectroscopically confirmed bright neighbors around quasars are statistically similar to those of inactive galaxies. The main conclusion brought to light through this dissertation is that at low-redshift Type I quasar activity is not impacted in a major way by its environment, but instead internal processes within the quasar host galaxy itself are the more probable mechanism for the AGN phenomenon. While it is possible that some major mergers fuel SMBHs at low-redshift, this is not the predominant scenario. Overall, this body of work contributes the crucial observational data to contrast and constrain the theoretical models of how AGN are triggered and their role in the life of the host galaxy as well as a potential impact on galaxies in its vicinity.



Last updated on 2024-03-12 at 13:19