Language

English (en)

Date of Award

Summer 5-12-2025

Author's School

School of Engineering & Applied Science

Author's Program

Physics

Degree Name

Bachelor of Science

Restricted/Unrestricted

Unrestricted

Abstract

In 2021 and 2024, the Event Horizon Telescope (EHT) collaboration published the first polarized images of the supermassive black holes (SMBHs) M87* and Sgr A*, which allowed us to place important constraints on the accretion flow and underlying space-time. Of particular interest is the dimensionless spin parameter "a•", which theoretically may attain a maximum value of a• = 0.998 when spun up by a thin accretion disk. On the other hand, mechanisms including incoherent accretion, SMBH mergers, and spin extraction via jets, are hypothesized to spin down SMBHs from these near-extremal values. In this work, we perform general relativistic magnetohydrodynamics (GRMHD) simulations of a• = 0.998 SMBHs with advection-dominated and strongly magnetized accretion disks to determine their observational characteristics. First, we evolve the fluid in a Kerr space-time to study black hole properties, including variability, magnetic flux accumulated on the horizon, and jet power. Then, we perform general relativistic ray-tracing (GRRT) to produce polarized movies that can be directly compared to current and future EHT observations. We predict increased jet power efficiency as well as distortions to the photon ring which should be an accessible signature that extensions to the EHT, such as the next-generation EHT (ngEHT) and Black Hole Explorer (BHEX), can then use to rule out such models.

Mentor

Angelo Ricarte, Yajie Yuan

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