Radiation GRMHD with Non-Thermal Particle Acceleration: Next-Generation Models of Black Hole Accretion Flows and Jets

University Of Colorado At Boulder, Boulder CO

Investigators

Abstract

One of the most striking phenomena revealed by radio telescopes are relativistic jets that can stretch over a million parsecs and have been shown to be physically connected with supermassive black holes (SMBH) in the centers of giant elliptical galaxies. Despite decades of effort, our understanding of the steps by which gas accreting onto a spinning SMBH is collimated into a narrow, magnetized beam of electrons and launched at near light-speed is still incomplete. General Relativistic Magneto-Hydrodynamic (GRMHD) fluid simulations have lately shown promise in being able to correctly account for the relevant physics and have successfully reproduced jet power and structure in low-luminosity active galactic nuclei (AGN), as well as predicting the Event Horizon Telescope's images of M87 and Sgr A*. The principal investigator will lead a team that will develop next-generation GRMHD code appropriate for a wider range of AGN luminosities that will link multi-wavelength observations of jets to properties of the central SMBH and its near environment. The award will also support the training of a postdoc in state-of-the-art computational techniques, provide opportunities for undergraduate research, and develop public planetarium shows. All GRMHD models and source code will be made publicly available. The next-generation GRMHD models will be used to predict radio to gamma-ray emission from a broad range of low-luminosity accretion flows and jets. These will be used to address longstanding questions about the structure of hot accretion flows, including the fundamental question of how relativistic electrons are loaded into jets causing them to radiate energy. The electron distribution function will be evolved using kinetic prescriptions for particle acceleration and a frequency- dependent, Monte Carlo method for radiative cooling. GRMHD simulations will be run for a sufficiently long duration to establish equilibrium properties up to ~100 gravitational radii from the black hole, in order to reliably predict the accretion flow and jet structure. Broadband spectra and polarized radio emission maps computed from the simulations as a function of (e.g.) mass accretion rate will be compared to observations of representative sources and used to make predictions for the visibility of the black hole shadow for next-generation long baseline radio interferometers. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.