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Three-Dimensional Simulations of Inflows Irradiated by a Precessing Accretion Disk in Active Galactic Nuclei: Formation of Outflows


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By Ryuichi Kurosawa & Daniel Proga, 2008, ApJ, 674, 97

Abstract

We present three-dimensional (3-D) hydrodynamical simulations of gas flows in the vicinity of an active galactic nucleus (AGN) powered by a precessing accretion disk. We consider the effects of the radiation force from such a disk on its environment on a relatively large scale (up to ~10 pc).  We implicitly include the precessing disk by forcing the disk radiation field to precess around a symmetry axis with a given period (P) and a tilt angle (Theta).  We study time evolution of the flows irradiated by the disk, and investigate basic dependencies of the flow morphology, mass flux, angular momentum on different combinations of Theta and P.  As this is our first attempt to model such 3-D gas flows, we consider a simplest form of radiation force i.e., force due to electron scattering, and neglect the forces due to line and dust scattering/absorption.  Further, the gas is assumed to be nearly isothermal.  We find the gas flow settles into a configuration with two components, (1) an equatorial inflow and (2) a bipolar inflow/outflow with the outflow leaving the system along the poles (the directions of disk normals). However, the flow does not always reach a steady state. We find that the maximum outflow velocity and the kinetic outflow power at the outer boundary can be reduced significantly with increasing Theta. We also find that of the mass inflow rate across the inner boundary does not change significantly with increasing Theta. The amount of the density-weighted mean specific angular momentum deposited to the environment by the precessing disk increases as P approaches to the gas free-fall time (t_ff), and then decreases as P becomes much larger than t_ff. Generally, the characteristics of the flows are closely related to a combination of P and Theta but not to P and Theta individually. Our models exhibit helical structures in the weakly collimated outflows. Although on different scales, the model reproduces the Z- or S- shaped density morphology of gas outflows which are often seen in radio observations of AGNs.

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Preprint

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Model Summary  

Click on the model numbers (e.g. agn0XX) in the table below to see the movies of each model.

Parameters for the central black hole
M_BH= 10^8 Msun, Mdot=1.6Msun/yr,  L_BH=2x10^12Lsun
Model
g
 M
 H
 f_d
 Gamma
 gam
 P
(yr)
 beta
(deg.)
 Note
P dependecy








agn040
 O
 X
 X
 0.95
 0.6
 1.01
 Inf.
 0
 Model I
agn041
 O
 X
 X
 0.95
 0.6
 1.01
 16000
 5
 Model II
agn043
 O
 X
 X
 0.95
 0.6
 1.01
 160000   5
 Model IV
agn047
 O
 X
 X
 0.95
 0.6
 1.01
 1600   5
Beta dependency








agn040
 O
 X
 X
 0.95
 0.6
 1.01
 16000
 0
 Model I
agn053
 O
 X
 X
 0.95
 0.6
 1.01
 16000
 2
agn041
 O
 X
 X
 0.95
 0.6
 1.01
 16000
 5
 Model II
agn042.c
 O
 X
 X
 0.95
 0.6
 1.01
 16000
 15
 Model III
gam dependency
agn041
 O
 X
 X
 0.95
 0.6
 1.01
 16000
 5
 Model II
agn048
 O
 X
 X
 0.95
 0.6
 5/3
 16000
 5
Gamma dependency
agn041
 O
 X
 X
 0.95
 0.6
 1.01
 16000
 5
 Model II
agn049
 O
 X
 X
 0.95
 0.9
 1.01
 16000
 5
agn050
 O
 X
 X
 0.95
 0.4
 1.01
 16000
 5

Note:    g_rad --> radiative acceleration,  H --> radiative heating,  f_d --> a ratio of disk luminosity to total luminosity,  Gamma  --> Eddington luminosity,   gam  -->  Adiabatic index, M  --> force multiplier of CAK ,  P   --> precession period,  beta --> disk tilt angle, O--> on ;  X --> off 

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