Time variability of accretion flows: effects of the adiabatic index and gas temperature

Abstract

We report on next phase of our study of rotating accretion flows onto black holes. We consider hydrodynamical (HD) accretion flows with a spherically symmetric density distribution at the outer boundary but with spherical symmetry broken by the introduction of a small, latitude-dependent angular momentum. We study accretion flows by means of numerical two-dimensional, axisymmetric, HD simulations for variety of the adiabatic index, $\gamma$ and the gas temperature at infinity, $c_{\infty }$. Our work is an extension of work done by Proga & Begelman who consider models for only $\gamma =5/3$. Our main result is that the flow properties such as the topology of the sonic surface and time behavior strongly depend on $\gamma$ but little on $c_{\infty }$. In particular, for $1<\gamma <5/3$, the mass accretion rate shows large amplitude, slow time-variability which is a result of mixing between slow and fast rotating gas. This temporal behavior differs significantly from that in models with $γ\simless 5/3$ where the accretion rate is relatively constant and from that in models with $γ\simgreat 1$ where the accretion exhibits small amplitude quasi-periodic oscillations. The key parameter responsible for the differences is the sound speed of the accretion flow which in turn determines whether the flow is dominated by gas pressure, radiation pressure or rotation. Despite these differences the time-averaged mass accretion rate in units of the corresponding Bondi rate is a weak function of $\gamma$ and $c_{\infty }$.

arXiv comment31 pages, 14 figures, accepted for publication in ApJ, for full resolution version goto http://users.camk.edu.pl/mmosc/ms.pdf

References in corpus (13)

• Advection-Dominated Accretion: A Self-Similar Solution
• The Formation of Galactic Disks
• On the Fate of Gas Accreting at a Low Rate onto a Black Hole
• Modelling the behaviour of accretion flows in X-ray binaries
• Gamma-Ray Bursts
• Advection-Dominated Accretion: Self-Similarity and Bipolar Outflows
• Thermal Equilibria of Accretion Disks
• Electron Heating in Hot Accretion Flows
• Accretion of low angular momentum material onto black holes: 2D magnetohydrodynamical case
• Accretion of low angular momentum material onto black holes: 2D hydrodynamical inviscid case
• Dynamics of Accretion Flows Irradiated by a Quasar
• Epicyclic Oscillations of Fluid Bodies: Newtonian Nonslender Torus
• On the morphology of accretion flows with small non-zero specific angular momentum

Cited by in corpus (13)

• Mechanical AGN Feedback: Controlling the Thermodynamical Evolution of Elliptical Galaxies
• Rotating Accretion Flows: From Infinity to the Black Hole
• Photon Trapping Enables Super-Eddington Growth of Black-Hole Seeds in Galaxies at High Redshift
• Parsec-scale accretion and winds irradiated by a quasar
• SPH Simulations of Black Hole Accretion: A Step to Model Black Hole Feedback in Galaxies
• Effects of adiabatic index on the sonic surface and time variability of low angular momentum accretion flows
• Time Evolution of the 3-D Accretion Flows: Effects of the Adiabatic Index and Outer Boundary Condition
• General relativistic hydrodynamic simulations of perturbed transonic accretion
• Nonaxisymmetric Effects in the Black Hole Accretion Inviscid Hydrodynamics: Formation and Evolution of a Tilted Torus
• Magnetized Accretion Flows: Effects of Gas Pressure
• Acoustic geometry obtained through the perturbation of the Bernoulli's constant
• Linear perturbations of low angular momentum accretion flow in the Kerr metric and the corresponding emergent gravity phenomena
• Low angular momentum flow model of Sgr A* activity