Bulletin of the American Physical Society
APS April Meeting 2023
Volume 68, Number 6
Minneapolis, Minnesota (Apr 15-18)
Virtual (Apr 24-26); Time Zone: Central Time
Session M14: Black Holes, AGN, and their Environments |
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Sponsoring Units: DAP Chair: Biprateep Dey, University of Pittsburgh Room: Marquette V - 2nd Floor |
Monday, April 17, 2023 10:45AM - 10:57AM |
M14.00001: Migration traps in AGN disks and hierarchical mergers as promising origin of the observed q-χeff correlation Alessandro Santini, Davide Gerosa, Roberto Cotesta The most recent analyses of binary black hole detections by LIGO and Virgo have highlighted the presence of a correlation between the mass ratio q and the effective spin χeff. In particular, data suggest that unequal-mass binaries show systematically larger values of the effective spin. We propose that this observed feature could be interpreted using hierarchical black hole mergers. We explore this in the context of AGN disks where a single black hole accretes a series of smaller black holes captured in a migration trap. We develop a toy model where the key free parameter is the average black-hole generation. Remarkably, such a simple parametric model appears to reproduce, at least qualitatively, the observed correlation. Our results indicate that migration traps in AGN disks could represent a promising formation channel for (some of) the LIGO/Virgo events. |
Monday, April 17, 2023 10:57AM - 11:09AM |
M14.00002: Aligning Retrograde Nuclear Cluster Orbits with an Active Galactic Nucleus Accretion Disk Syeda S Nasim, Gaia Fabj, Freddy Caban, Amy Secunda, K. E. Saavik Ford, Barry McKernan, Jillian M Bellovary, Nathan W. C. Leigh, Wladimir Lyra Stars and stellar remnants orbiting a supermassive black hole (SMBH) can interact with an active galactic nucleus (AGN) disk. Over time, prograde orbiters (inclination i < 90°) decrease inclination, as well as semi-major axis (a) and eccentricity (e) until orbital alignment with the gas disk. Captured stellar-origin black holes (BH) add to the embedded AGN population which drives BH-BH mergers detectable in gravitational waves using LIGO-Virgo-KAGRA (LVK) or BH-SMBH mergers detectable with LISA (Laser Interferometer Space Antenna). Captured stars can be tidally disrupted by BH or the SMBH or rapidly grow into massive ’immortal’ stars. Here, we investigate the behavior of polar and retrograde orbiters (i ≥ 90°) interacting with the disk. We show that retrograde stars are captured faster than prograde stars, flip to prograde during capture and decrease a dramatically towards the SMBH. For BH, we find a critical angle iret ∼ 110°, below which retrograde BH decay towards embedded prograde orbits (i → 0°), while for i > iret BH decay towards embedded retrograde orbits (i → 180°). BH near polar orbits (i ∼ 90°) and stars on nearly embedded retrograde orbits (i ∼ 180°) show the greatest decreases in a. Whether a star is captured by the disk within an AGN lifetime depends on disk density and stellar type. For BH, capture time is longest for polar orbits, low mass BH and lower density disks. Larger mass BH should typically spend more time in AGN disks, with implications for the embedded BH spin distribution. |
Monday, April 17, 2023 11:09AM - 11:21AM Author not Attending |
M14.00003: One Two Quench: A Double Minor Merger Scenario Natalie N Sanchez, Michael Tremmel, Jess Werk, Andrew Pontzen, Charlotte Christensen, Tom Quinn, Sarah Loebman, Akaxia Cruz In this talk, I will discuss the effects of environment and supermassive black hole (SMBH) feedback working together to quench a set of Milky Way-mass (MW-mass) galaxies. Specifically, we examine the cessation of star formation in Milky Way analogs from the cosmological volume, Romulus25, and a set of four zoom-in simulations run using the N-body+Smoothed particle hydrodynamics code, ChaNGa. These four zoom-in galaxy simulations implement a novel technique called genetic modification to generate galaxies from nearly identical initial conditions. These genetically modified (GM) galaxies are characterized by minor modifications to their accretion histories while maintaining the large scale structure and final main halo mass of the original simulation. This technique allows for a truly controlled experiment that can isolate specific physical processes that influence galaxy evolution. Exploring MW-mass galaxies from both of these simulation suites, we find that the combination of large-scale galaxy accretion--in the form of minor merger interactions--and feedback from the SMBH can work in tandem to fully quench star formation. |
Monday, April 17, 2023 11:21AM - 11:33AM |
M14.00004: Ray-tracing around a Binary Black Hole Analytical Mini-Disk Model Kaitlyn D Porter, Manuela Campanelli, Scott C Noble, Eduardo M Home, Luciano Combi Supermassive black holes (SMBHs) are thought to be located at the centers of most galactic nuclei. When galaxies merge they form supermassive black hole binary (SMBHB) systems. Galaxy mergers are gas rich environments and there is likely to be matter surrounding the binary system as well as accreting onto the individual black holes. Therefore, SMBHBs are potential sources of electromagnetic (EM) radiation. The EM signatures depend on gas dynamics, orbital dynamics, and radiation processes. The gas dynamics are governed by general relativistic magnetohydrodynamics in a time-dependent spacetime. Numerically solving the magnetohydrodynamic equation for a time-dependent binary spacetime is computationally expensive. Therefore, it is challenging to conduct a full exploration of the parameter space of these systems and the resulting EM signatures. |
Monday, April 17, 2023 11:33AM - 11:45AM |
M14.00005: New Analytical Insights Into Circumbinary Disk Dynamics Siddharth Mahesh, Michal Pirog, Sean T McWilliams The study of gas disks surrounding a supermassive black-hole binary (SMBHB) and their evolution during both the inspiral and merger stages can inform electromagnetic searches for candidate SMBHBs, in addition to being relevant for the expected gravitational-wave signal. We describe a new analytical approach to the dynamics of circumbinary accretion disks, which draws from the study of test particle orbits in the restricted 3 body problem. The study aims to connect the stability of orbits in this picture to the dynamics of gas flows near the circumbinary gap and reconcile some of the results from full hydrodynamics simulations of these disks over different mass ratios and disk-binary inclinations. The results indicate a truncation of the central cavity at timescales shorter than the viscous timescale which has implications for the disk-binary interactions at all stages of the binary's evolution. |
Monday, April 17, 2023 11:45AM - 11:57AM |
M14.00006: Mapping the Host Galaxies of Nanohertz Gravitational Wave Sources Polina Petrov, Stephen R Taylor, Maria Charisi, Chung-Pei M Ma Supermassive black hole binaries (SMBHBs) present us with exciting opportunities for multi-messenger science. These binaries are thought to form as a natural consequence of galaxy mergers, with the potential to produce bright electromagnetic (EM) emission as well as individually resolvable gravitational waves (GWs) that can be detected with pulsar timing arrays (PTAs). We may find SMBHBs in a wide variety of systems, and each type of system may generate a distinct EM signature, or none at all. This makes direct multi-messenger searches challenging, but the answer could lie in our ability to identify the galaxy hosting the SMBHB. In this talk, I will show how we can connect PTA observations with large galaxy catalogs to optimize host galaxy identification following the first detection of a single-source GW signal. I will discuss how this approach has the potential to accelerate the first multi-messenger observations of a SMBHB. |
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