Dissertation
Evidence for merger-induced AGN fueling using integral field spectroscopy
University of Iowa
Doctor of Philosophy (PhD), University of Iowa
Spring 2022
DOI: 10.17077/etd.006376
Abstract
Hydrodynamical simulations of galaxy mergers have suggested that merger-induced gas-inflows may be able to fuel the central supermassive black hole (SMBH), triggering an active galactic nucleus (AGN). Despite the results of these simulations, observational studies disagree on whether or not there is merger-induced AGN. We use the recently completed integral field spectroscopic (IFS) survey, MaNGA (Mapping Nearby Galaxies at Apache Point Observatory), to study the volume densities and [OIII] luminosities of AGN in paired galaxies. We build a sample of 387 spectroscopically confirmed galaxy pairs of which 102 host an AGN and a sample of 24 dual AGN (dAGN). We find that the volume density of AGN in galaxy pairs is higher than what would be expected by the random pairing of stochastically triggered AGN. At close separations, the volume density of AGN in pairs is 2.5x what is expected from the random pairing of AGN. We further find that the volume density of dAGN under separations of 4 kpc is 40x what we would expect from the random pairing of stochastically triggered AGN. We find that neither correlated AGN activity nor merger-induced fueling can fully explain the excess AGN volume density. Instead, we find that a model that includes stochastic fueling, merger-induced fueling, and correlated AGN activity is required to fully explain the excess AGN in our sample of galaxy pairs. We also find that the AGN in our galaxy pairs feature enhanced levels of [OIII] luminosity in comparison to the AGN in isolated control galaxies to the order of 0.1-0.4 dex. The enhanced volume density and [OIII] luminosity demonstrates the impact that galaxy interactions have on the development of the supermassive black holes (SMBH) found in the centers of galaxies.
Details
- Title: Subtitle
- Evidence for merger-induced AGN fueling using integral field spectroscopy
- Creators
- Joshua L. Steffen
- Contributors
- Hai Fu (Advisor)Julia M Comerford (Committee Member) - University of Colorado BoulderCasey T DeRoo (Committee Member)Keri Hoadley (Committee Member)Philip Kaaret (Committee Member)
- Resource Type
- Dissertation
- Degree Awarded
- Doctor of Philosophy (PhD), University of Iowa
- Degree in
- Physics
- Date degree season
- Spring 2022
- DOI
- 10.17077/etd.006376
- Publisher
- University of Iowa
- Number of pages
- x, 98 pages
- Copyright
- Copyright 2022 Joshua L. Steffen
- Language
- English
- Description illustrations
- illustrations (chiefly color), tables, graphs
- Description bibliographic
- Includes bibliographical references (pages 89-98).
- Public Abstract (ETD)
- Simulations have predicted that the merging of two galaxies should induce gas-inflows which can fuel the central supermassive black hole (SMBH) causing an active galactic nu- cleus (AGN). Despite the results of these simulations, past observational studies have found conflicting evidence for merger-driven AGN activity in galaxy pairs. I use the recently com- pleted MaNGA (Mapping Nearby Galaxies at Apache Point Observatory) survey to study this phenomena. MaNGA uses bundles of fiber-optic cables to capture the spectra of its targets allowing for spatially resolved data. With this survey, I build a sample of merging and interacting galaxies and a sample of galaxies hosting an AGN. I also build a sample of isolated galaxies since there are also internal processes which may stochastically induced AGN activity. With these samples, I find a higher rate of AGN in our paired galaxies com- pared to what would be expected from the random pairing of stochastically induced AGN. We also study the [O iii] luminosities in these AGN as a tracer of the SMBH’s mass accretion rate and find that the AGN in our pairs feature stronger [O iii] luminosities than the AGN in isolated galaxies. This gives us strong evidence for merger-driven AGN activity which is in agreement with the predictions of past simulations. These results also demonstrate that galaxy mergers play a significant role in the mass growth of the SMBHs found in the centers of the galaxies in the present universe.
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9984271353902771
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