General relativistic magnetohydrodynamic (GRMHD) simulations of black hole accretion and jets Público

Abstract

Active galaxies with extremely high luminosity at the center have more energy than normal galaxies do. This central compact region, or active galactic nuclei (AGN), has a supermassive black hole that powers the AGN to emit such great energy. Some AGN form astrophysical jets that scale from AU to Mpc with energies ranging from few meters to tera-electronvolts. The formation of jets depends on the spin of a supermassive black hole as well as the accretion disk, but the exact mechanism remains unclear. In this project, we investigated how the spin affects the energy output of a rotating black hole using general relativistic magnetohydrodynamic (GRMHD) simulation, HARMPI. We simulated the spherically symmetric accretion (Bondi model) and determined the sonic radius of infalling matter onto a rotating black hole. We also simulated the torus around a black hole with jets and studied the relationship between the spin of a black hole, accretion rate, and energy output. Results from the simulation indicate a positive correlation between the black hole spin and the energy output and between the accretion rate and the energy output. However, no clear relation has been identified between the black hole spin and the accretion rate. We further suggest extensive studies on the accretion rate and the energy output as well as varying magnetic field strengths.

Table of Contents

1 Introduction and background 1

2 Magnetohydrodynamics (MHD) 5

2.1 Introduction............................ 5

2.2 General Relativistic MHD (GRMHD)............................ 6

2.3 High accuracy relativistic magnetohydrodynamics (HARM)............................ 8

2.3.1 Governing equations............................ 10

2.3.2 Implementation............................ 11

3 HARMPI simulation of Bondi accretion flows 13

3.1 Spherical accretion onto black holes............................ 13

3.2 Problem approach and simulation setups............................ 14

3.3 Convergence study .................................. 15

3.4 Results......................................... 17

3.5 Sonic radius...................................... 21

3.5.1 Analytical solution .............................. 21

3.5.2 Numerical solution.............................. 23

3.6 Physical implications ................................. 24

4 HARMPI simulation of torus and jets 26

4.1 Spin of a black hole.................................. 26

4.2 Problem approach and simulation setups....................... 29

4.3 Results......................................... 30

4.4 Comparison to observational studies ......................... 36

5 Discussion 38

A Appendix 41

References 53

About this Honors Thesis

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School	Emory College
Department	Physics
Degree	B.S.
Submission	Honors Thesis
Language	English
Research Field	Physics, Astronomy and Astrophysics Physics, Astrophysics Physics, General
Palabra Clave	magnetohydrodynamics (MHD) Black Hole
Committee Chair / Thesis Advisor	Bonning, Erin, Emory University
Committee Members	Fossati, Davide, Emory University Bans, Alissa, Emory University

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