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 K14: Black Holes and Jets |
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Sponsoring Units: DAP Chair: Manel Errando, Washington University in Saint Louis Room: Marquette V - 2nd Floor |
Sunday, April 16, 2023 3:45PM - 3:57PM |
K14.00001: The Black Hole Photon Ring I: A Science Case Alex Lupsasca, Alejandro Cardenas-Avendano What does a black hole look like? The first images of the supermassive black holes M87* and Sgr A* display a bright ring encircling the event horizon, which appears as a dark patch in its surrounding emission. But Einstein's theory of general relativity predicts that within this image there also lies a thin ''photon ring'' consisting of multiple mirror images of the main emission. These images arise from photons that orbited around the black hole multiple times, probing the warped space-time geometry just outside its horizon. The photon ring carries an imprint of the strong gravity in this region and encodes fundamental properties of the black hole. In this talk, I will discuss a recent proposal to measure this predicted (but not yet observed) ring and how it could provide a precise test of general relativity. The proposed measurement will be the target of a next-generation space-VLBI mission proposed to fly within the next decade. |
Sunday, April 16, 2023 3:57PM - 4:09PM |
K14.00002: The Black Hole Photon Ring II: Astrophysical Fluctuations Alejandro Cardenas-Avendano, Alex Lupsasca Using black hole images to test general relativity in the dynamical, strong-field regime poses a significant challenge: how can the effects of the gravitational field be disentangled from the astrophysical details of the radiating source? The photon ring, whose angle-dependent diameter follows a shape predicted by general relativity, is a promising observable with a weak dependence on astrophysics. In this talk, I will present an extensive parameter-estimation survey of astrophysical models in which this ring shape can be recovered with high precision. The analysis was carried out using the numerical framework AART to simulate black hole movies of stochastic, non-stationary, non-axisymmetric equatorial sources. These results are relevant to the ongoing effort to develop space-based, very-long-baseline-interferometry missions targeting the photon rings of supermassive black holes. |
Sunday, April 16, 2023 4:09PM - 4:21PM |
K14.00003: Dissipation in Global Simulations of Accretion Disks Catherine Gibson, Theodore Dezen We perform general relativistic magneto-hydrodynamic simulations to study the dynamics of and radiation from accretion onto stellar mass black holes. Recent theoretical work suggests magnetic torques exerted at the innermost stable circular orbit can drive significant bulk vertical energy transport in regions close to the black hole, and hence dissipate a larger fraction of accretion power near the photosphere compared to standard models. This additional heating in turn may lead to the non-thermal high-energy (into several hundred keVs) radiation observed in some systems. We develop methods for calculating dissipation profiles from time-dependent global simulations of accretion disks and analyze these calculations to further assess the feasibility of such models and illuminate the underlying physical mechanisms. |
Sunday, April 16, 2023 4:21PM - 4:33PM |
K14.00004: Black Hole Demographics in the First Galaxies Tien Nguyen, John Wise, Danielle Skinner, Sandrine Ferrans Black holes are regions in the universe with such immense gravity that nothing can escape from. Black holes range in size from stellar-mass to supermassive. Supermassive black holes have been found within the first billion years of the universe, which challenges current theories of black hole astrophysics. There have been many theories for why supermassive black holes could exist at such an early time such as the growth of stellar-mass black holes, the direct collapse of a primordial gas cloud, or the stellar collisions and dynamical instabilities in dense star clusters. We are interested in the scenario that supermassive black holes grow from stellar-mass black holes by accumulating their surrounding material in a process called accretion and by mergers of black holes. We used the computer simulation code Enzo to simulate the formation and growth of stellar-mass black holes, and analyzed the simulation using the Python toolkit yt. In our data analysis, we look at the mass growth and orbital evolution of the black holes, and from that determine if the black holes will "sink" to the galaxy center after their formation and especially after a galaxy merger. Our work will contribute to our current understanding of how stellar-mass black holes can grow into supermassive black holes in the early universe. Moreover, since black holes may merge in the early universe, our results will also constrain the relationship between gravitational wave events and early galaxy formation. |
Sunday, April 16, 2023 4:33PM - 4:45PM |
K14.00005: Particle Acceleration in Multimessenger & MeV Blazars Tiffany R Lewis The acceleration mechanisms in blazars jets are currently uncertain. In order to study particle acceleration in this environment, we have to filter through the additional uncertainty in the high-energy emission processes. What has become clear regardless is that to understand either requires simulating both acceleration and cooling processes accurately in the particle population. The advent of new data types, like high-energy polarization and coincident neutrinos point toward shock acceleration and leptohadronic composition for at least some blazars. Thus, I present some theoretical models that treat these cases for a sample of MeV bright and Multimessenger blazars relevant for the AMEGO-X mission concept and future MeV missions. |
Sunday, April 16, 2023 4:45PM - 4:57PM |
K14.00006: Quantifying Errors and Biases in Pitch Angle Measurements Seburne James, Julia Kennefick Supermassive black holes (SMBHs) have masses which correlate well with properties of their host galaxies, suggesting the galaxies and their central black holes grew up together. Because of this, studying how SMBH masses increase over time is an important tool for understanding galaxy evolution. Several groups have determined a black hole mass function for the local universe, but our ability to extend it to the distant universe (and thereby see how it has varied through time) is hampered by the difficulty of directly measuring black hole masses. One promising way to estimate SMBH masses is to use the relationship between the pitch angle of a spiral galaxy and the mass of its SMBH. In order to use this relation we need to have a good understanding of what errors and selection biases affect our pitch angle measurements. One method of measuring pitch angles of spiral galaxies is via the MATLAB code Spirality. By utilizing Spirality on simulated galaxy images, we have mapped Spirality's margins of error and selection biases against various galaxy properties, such as (true) pitch angle, arm-interarm contrast, and magnitude. The goal is to use this information to correct pitch angle measurements made on real galaxies. |
Sunday, April 16, 2023 4:57PM - 5:09PM |
K14.00007: Exascale Simulations of Magnetized AGN Feedback Forrest Glines, Philipp Grete, Brian W O'Shea, Deovrat Prasad, Benjamin Wibking Diffuse plasmas in a wide range of astrophysical systems from galaxy clusters, galaxy groups, and galaxies can be greatly affected by embedded magnetic fields. The magnetically collimated jets emitted by active galactic nuclei (AGN) at the center of these systems are widely agreed to play a key role in the regulation of star and cold gas formation in these structures. The effect of the AGN’s magnetic fields on the system’s magnetic fields and ambient plasma, however, is still being explored. Magnetic fields injected by the AGN jet can affect dynamics on large scales on hundreds of kiloparsecs with the magnetized AGN jet down to small scales on parsecs or smaller with the small-scale turbulent dynamo. Modeling large portions of this huge span of dynamical ranges requires vast computing resources such as those provided by exascale supercomputers. To perform such simulations of magnetized AGN feedback on exascale supercomputers, we developed AthenaPK, an open source magnetohydrodynamics code capable of running at high performance on exascale supercomputer architectures. We present simulations of magnetized AGN feedback within galaxy groups and clusters with a focus on how magnetized AGN jets affect the energetics of the plasma. With exascale resources, we can model the plasma at much higher resolution with higher fidelity than previously possible, allowing us to resolve more physics within these systems. |
Sunday, April 16, 2023 5:09PM - 5:21PM |
K14.00008: An Analytical and Simulations-based Explanation of Observed X-ray Reflection Signatures at kpc Scales Around AGN Panayiotis Tzanavaris, Stephanie LaMassa, Tahir Yaqoob The X-ray based literature of Active Galactive Nuclei (AGN) contains countless examples of "reflection" relatively close to the central supermassive black hole, from the accretion disk to the putative torus at ~pc scales. Puzzlingly though, there is also just a handful of observations of telltale features such as the Fe Kα fluorescent emission line consistent with being located at vastly greater, kiloparsec scales. We demonstrate for the first time that relatively simple analytical, physically motivated arguments can lead to robust predictions of these signatures, surprisingly consistent with observations. We further discuss that detailed Monte Carlo simulations of the physics of X-ray reflection are also fully consistent with the analytical estimates, and illustrate with comparisons to Chandra X-ray observations. |
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