Abstract

It is hypothesized that following a galaxy merger the two central supermassive black holes (SMBH) become a binary system, eventually coalescing due to emission of gravitational waves. This coalescence results in a single black hole, with an accretion disk shining with high luminosity that photoionizes the surrounding gas. Therefore, the newly merged SMBH is visible as an active galactic nucleus (AGN). However, the gravitational waves are emitted anisotropically by the binary as it inspirals, resulting in a recoil kick. This ejects the newly merged SMBH from the AGN’s center of the galaxy. The SMBH oscillates around the galaxy’s center of mass, taking with it the accretion disk and inner broad line region, but leaving behind the larger narrow line region. Identifying and studying recoiling SMBH provides us with signposts of SMBH binary mergers, yielding information about the frequency at which these events occur in galaxies, thus allowing us to learn more about galaxy evolution. These recoils can be studied with LISA, the spaced-based successor to LIGO, and may be detected by pulsar timing arrays within the next few years. For now, these events can be detected by analyzing the spectrum of the AGN for Doppler shifts and other properties of the emission lines. In recoil candidates, we expect the broad emission lines to have large Doppler shifts, greater full width at half-maxima, lower kurtosis, and asymmetric peaks. Only a few candidates have been identified so far using the first two criteria. The work in this thesis presents a search for more recoil candidates using all four criteria. A spectroscopic data sample from the Sloan Digital Sky Survey Quasar Catalog Data Release 7 established by Liu et al. 2019 was analyzed for recoil candidates. The spectral fitting code, PyQSOFit was used to fit each AGN spectrum and measure the four broad line properties. We present and analyze ~230 possible recoil candidates selected from a sample dataset. We discuss the likelihood of detecting a recoiling SMBH in this sample based on the four mentioned criteria.

Publication Date

7-2024

Document Type

Thesis

Student Type

Graduate

Degree Name

Astrophysical Sciences and Technology (MS)

Department, Program, or Center

Physics and Astronomy, School of

College

College of Science

Advisor

Andrew Robinson

Advisor/Committee Member

Manuela Campanelli

Advisor/Committee Member

Michael Richmond

Campus

RIT – Main Campus

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