NUMERICAL SIMULATION OF HOT ACCRETION FLOWS. I. A LARGE RADIAL DYNAMICAL RANGE AND THE DENSITY PROFILE OF ACCRETION FLOW

By F. Yuan, Maochun Wu, De-Fu Bu. 2012

132 citations recorded by the source corpus.

Numerical simulations of hot accretion flow, both hydrodynamical and magnetohydrodynamical, have shown that the mass accretion rate decreases with decreasing radius; consequently, the density profile of accretion flow becomes flatter than in the case of a constant accretion rate. This result has important theoretical and observational implications. However, because of technical difficulties, the radial dynamic range in almost all previous simulations usually spans at most two orders of magnitude. This small dynamical range, combined with the effects of boundary conditions, makes the simulation results suspect. In particular, the radial profiles of density and inflow rate may not be precise enough to be used to compare with observations. In this paper, we present a “two-zone” approach to expand the radial dynamical range from two to four orders of magnitude. We confirm previous results and find that from rs to 104rs the radial profiles of accretion rate and density can be well described by and ρ∝r−p. The values of (s, p) are (0.48, 0.65) and (0.4, 0.85) for the viscous parameters α = 0.001 and α = 0.01, respectively. More precisely, the accretion rate is constant (i.e., s = 0) within ∼10rs, but beyond 10rs we have s = 0.65 and 0.54 for α = 0.001 and 0.01, respectively. We find that the values of both s and p are similar in all numerical simulation works irrespective of whether a magnetic field is included or not and what kind of initial conditions are adopted. Such an apparently surprising “common” result can be explained by the most recent version of the adiabatic inflow–outflow model. The density profile we obtain is in good quantitative agreement with that obtained from the detailed observations and modeling of Sgr A* and NGC 3115. The origin and implications of such a profile will be investigated in a subsequent paper.

Subfields: Astronomy and Astrophysics, Geophysics

View Paper: https://www.semanticscholar.org/paper/7335effb3b51498703390829268738ad7d306701

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In Astronomy and Astrophysics

1. Ramesh Narayan
2. A. Sa̧dowski
3. F. Yuan
4. Yucong Zhu
5. F. Xie
6. R. Penna
7. A. Tchekhovskoy
8. A. Kulkarni

In Geophysics

1. F. Yuan
2. Ramesh Narayan
3. A. Sa̧dowski
4. R. Penna
5. Yucong Zhu
6. A. Kulkarni

Citations in the corpus

• Hot Accretion Flows Around Black Holes (2014, methodology): “Typically, the jet dominates the energy output, whereas the wind dominates the momentum output (Yuan et al. 2012a, Sadowski et al. 2013a).”
• Radiative efficiency of hot accretion flows (2012, background): “Yuan et al. (2012b) have found that the profile of Ṁ(R) has two parts.”
• GRMHD simulations of magnetized advection‐dominated accretion on a non‐spinning black hole: role of outflows (2012, background): “Yuan et al. (2012b) estimate from their large dynamic range 2D hydrodynamic simulations that s ∼0.4–0.5.”
• Energy, momentum and mass outflows and feedback from thick accretion discs around rotating black holes (2013, background): “Roughly, it appears that 0.5 < s < 0.7 (in agreement with Yuan et al. 2012b).”