Abstract:
The gravitational pull of a black hole attracts gas and forms a physical laboratory whose extreme conditions cannot be replicated on Earth. The infalling gas forms an accretion disk where the interplay between hydromagnetic processes and the warping of space-time releases gravitational energy in the form of radiation, relativistic jets, and winds. It is likely that most gas falls into supermassive black holes when the accretion rate approaches the Eddington limit (L=Ledd), at which point radiation pressure overcomes gravity. To date, our knowledge of such `luminous’ black hole accretion disks mostly relies on semi-analytical models, supplemented by a very limited set of numerical simulations.
In my talk I will discuss new insights gained from the first radiative general relativistic magnetohydrodynamics (GRMHD) simulations of luminous accretion disks. I will demonstrate that magnetic fields lead to the formation of a hot corona and that misalignment between the disk and black hole spin axis can explain quasi-periodic oscillations, which have remained a mystery for over 30 years.
I will finish my talk by discussing the opportunities the next-generation of GRMHD simulations will bring in addressing the origin of non-thermal radiation, cosmic rays, and neutrinos from accreting black holes.
Bio:
Matthew Liska is a computational astrophysicist with an interdisciplinary interest in astrophysics, plasma physics and computation. He is the main developer of the world's first GPU accelerated GRMHD code ("H-AMR") which he uses to study accretion onto compact objects such as black holes. He completed his PhD in 2019 at the University of Amsterdam and is now a John Harvard & ITC Fellow at Harvard CFA.
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2023-03-01T11:00:002023-03-01T12:00:00How do the most luminous black holes accrete and expel gas?Event Information:
Abstract:
The gravitational pull of a black hole attracts gas and forms a physical laboratory whose extreme conditions cannot be replicated on Earth. The infalling gas forms an accretion disk where the interplay between hydromagnetic processes and the warping of space-time releases gravitational energy in the form of radiation, relativistic jets, and winds. It is likely that most gas falls into supermassive black holes when the accretion rate approaches the Eddington limit (L=Ledd), at which point radiation pressure overcomes gravity. To date, our knowledge of such `luminous’ black hole accretion disks mostly relies on semi-analytical models, supplemented by a very limited set of numerical simulations.
In my talk I will discuss new insights gained from the first radiative general relativistic magnetohydrodynamics (GRMHD) simulations of luminous accretion disks. I will demonstrate that magnetic fields lead to the formation of a hot corona and that misalignment between the disk and black hole spin axis can explain quasi-periodic oscillations, which have remained a mystery for over 30 years.
I will finish my talk by discussing the opportunities the next-generation of GRMHD simulations will bring in addressing the origin of non-thermal radiation, cosmic rays, and neutrinos from accreting black holes.
Bio:
Matthew Liska is a computational astrophysicist with an interdisciplinary interest in astrophysics, plasma physics and computation. He is the main developer of the world's first GPU accelerated GRMHD code ("H-AMR") which he uses to study accretion onto compact objects such as black holes. He completed his PhD in 2019 at the University of Amsterdam and is now a John Harvard & ITC Fellow at Harvard CFA.
Learn More:
See Matthew's webpage here
Event Location:
HENN 318
