Radiation Hydrodynamic simulations of super-Eddington Accretion Flows super-Eddington Accretion Flows Radiation Hydrodynamic simulations of super-Eddington Accretion Flows super-Eddington Accretion Flows Ken OHSUGA Rikkyo University, Japan ① Super-Eddington accretion flows with photon-trapping (Ohsuga et al. 2005, ApJ, 628, 368) ② Limit-cycle oscillations driven by disk instability (Ohsuga 2006, ApJ, 640, 923)

Super-Eddington disk accretion flows The super-Eddington disk accretion (Mdot > L E /c 2 ; L E :Eddington luminosity) is one of the important physics for formation of the SMBHs. The super-Eddington accretion might be an engine of the high L/L E objects, ULXs, GRBs, NLS1s, ….. Mass outflow and radiation of the super-Eddington accretion flow are thought to affect the evolution of the host galaxies. To understand the super-Eddington accretion is very important ! 1. Super-Eddington Accretion Flows In the super-Eddington accretion, the radiation pressure affects the dynamics of the flow. Multi- dimensional effects are important.

BH Accretion Disk Viscous Heating Photon-Trapping Photons fall onto BH with accreting gas Outflow Gas Radiation Energy We investigate the super-Eddington disk accretion flows by performing the 2D Radiation Hydrodynamic simulations. *Slim disk model (1D) cannot correctly treat the multi-dimensional effects

Basic Equations of Radiation Hydrodynamics Continuity Equation ・・・・・・・ Equation of Motion ・・・・・・・ Gas Energy Equation ・・・・・・ Radiation Energy Equation ・・ Radiation Force Viscosity Absorption/Emission Radiative Flux Equation of State: p=(  1)e,  =5/3 Radiation fields (F 0, P 0 ) ： FLD approximation  -viscosity ：  P (  =0.1, P:total pressure) Absorption coefficient(  =  ff +  bf ),  ff : free-free absorption,  bf :bound-free absorption (Hayashi, Hoshi, Sugimoto 1962)

Numerical Method Explicit-implicit finite difference scheme on Eulerian grid (Spherical coordinates : 96 x 96 mesh) Axisymmetry with respect to the rotation axis Size of computational domain: 500r s Initial condition: atmosphere (no disk) Free outer boundary & absorbing inner boundary Injection BH r/rs r/rs z/rs z/rs 500 Matter (0.45 x Keplerian angular momentum) is continuously injected into the computational domain from the outer disk boundary. Parallel computing with PC cluster

Radiation Energy DensityGas Density The quasi-steady structure of the super-Eddington accretion flows is obtained by our simulations.

Density & Velocity fields Outflow KH instability Quasi-steady Structure Mass-Accretion Rate Mass-accretion rate decreases near the BH. BH r/rs r/rs z/rs z/rs Ohsuga et al. 2005, ApJ, 628, 368 Bubbles & Circular Motion

Radiation Pressure- driven wind Radiation Pressure- dominated Disk High Temperature Outflow/Corona Radiation Energy Density Radiation Pressure Gas Pressure Gas Temperature Radial Velocity Escape Velocity Low Temperature Disk Quasi-steady Structure

Photon-Trapping Mass-accretion rate Luminosity [L/L E ] 2D RHD simulations BH z/rs z/rs r/rs r/rs Transport of Radiation Energy in r-direction Radiation energy is transported towards the black hole with accreting gas (photon-trapping). We verify that the mass-accretion rate considerably exceeds the Eddington rate and the luminosity exceeds L E. Radiation Kinetic (Outflow) Viscous Heating

Viewing-angle dependent Luminosity & Image BH  The observed luminosity is sensitive to the viewing-angle. It is much larger than L E in the face-on view. Intensity Map Apparent Luminosity Density 4  D 2 F(  )/L E Our simulations [][] (Intrinsic Luminosity ~3.5L E )

2. Limit-Cycle Oscillations Timescale of the luminosity variation is around 40s. The disk luminosity oscillates between 2.0L E and 0.3L E (Yamaoka et al. 2001). The intermittent JET is observed. Janiuk & Czerny 2005 GRS (micro quasar) L~2L E L~0.3L E 40s

Disk instability in the radiation-pressure dominant region. If the mass-accretion rate from the disk boundary is around the Eddington rate, Mdot  L E /c 2, the disk exhibits the periodic oscillations via the disk instability. stable unstable Surface density Mass-accretion rate High state Low state This Topic (Mdot=10 2 L E /c 2 ) Previous Topic (Mdot=10 3 L E /c 2 ) We investigate the time evolution of unstable disks by performing the 2D RHD simulations.

Sub-Eddington state It is found that the disk structure changes periodically. Super-Eddington state outflow

The disk luminosity oscillates between 0.3L E and 2.0L E, and duration time is 30-50s. Jet appears only in the high luminosity state. These results are nicely fit to the observations of GRS Mass accretion rate Outflow rate Trapped luminosity Luminosity Ohsuga 2006, ApJ, 640, 923

Conclusions(1) : super-Eddington accretion flow; Mdot >> L E /c 2  The mass accretion rate considerably exceeds the Eddington rate.  The black hole can rapidly grow up due to disk accretion (Mdot/M~10 6 yr).  The luminosity exceeds the Eddington luminosity. The apparent luminosity is more than 10 times larger than L E in the face-on view.  The luminosity of the ULXs can be understood by the super-Eddington accretion flow.  The thick disk forms and the complicated structure appears inside the disk. The radiation-pressure driven outflow is generated above the disk.  We found that the photon-trapping plays an important role. Conclusions(2) : limit cycle oscillations; Mdot  L E /c 2  The resulting variation amplitude (0.3L E ⇔ 2.0L E ) and duration (30-50s) nicely fit to the observations of microquasar, GRS  The intermittent jet is generated.  The physical mechanism, which causes the limit-cycle oscillations, is the disk instability in the radiation-pressure dominant region.