2017/09/08 by Yan-Fei Jiang, James Stone, Shane W. Davis · 2 citations
Physics and Astronomy · #astro-ph.HE
paper · pdf · doi:10.3847/1538-4357/ab29ff
21 pages, 17 figures, submitted to ApJ, movies available here https://goo.gl/5yR3ig
arxiv created 2017/09/08 · arxiv updated 2019/09/11
We use global three dimensional radiation magneto-hydrodynamical simulations to study accretion disks onto a 5× 108M\odot black hole with accretion rates varying from ∼ 250LEdd/c2 to 1500 LEdd/c2. We form the disks with torus centered at 50-80 gravitational radii with self-consistent turbulence initially generated by the magneto-rotational instability. We study cases with and without net vertical magnetic flux. The inner regions of all disks have radiation pressure ∼ 104-106 times the gas pressure. Non-axisymmetric density waves that steepen into spiral shocks form as gas flows towards the black hole. In simulations without net vertical magnetic flux, Reynolds stress generated by the spiral shocks are the dominant mechanism to transfer angular momentum. Maxwell stress from MRI turbulence can be larger than the Reynolds stress only when net vertical magnetic flux is sufficiently large. Outflows are formed with speed ∼ 0.1-0.4c. When the accretion rate is smaller than ∼ 500 LEdd/c2, outflows start around 10 gravitational radii and the radiative efficiency is ∼ 5%-7% with both magnetic field configurations. With accretion rate reaching 1500 LEdd/c2, most of the funnel region close to the rotation axis becomes optically thick and the outflow only develops beyond 50 gravitational radii. The radiative efficiency is reduced to 1%. We always find the kinetic energy luminosity associated with the outflow is only ∼ 15%-30% of the radiative luminosity. The mass flux lost in the outflow is ∼ 15%-50% of the net mass accretion rates. We discuss implications of our simulation results on the observational properties of these disks.