Simulations of Accreting Black Holes on Horizon Scales

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1 Simulations of Accreting Black Holes on Horizon Scales Jonathan C. McKinney UMD McKinney, Alexander Tchekhovskoy, Roger Blandford (2012) (Science Express Nov 15, 2012) Viz: Ralf Kaehler (Stanford) and JCM

2 Precision BH Physics? Soon: Complete, self-consistent Radiative Disk-Jet Models Horizon-scale observations of BHs (Vincent Fish s talk) Concordance for M, a, etc. (polarized spectra, QPOs, imaging) Signatures & Methods to test GR (Emanuele Berti and other talks) This Talk: Effect of Magnetic Field & BH s Spin Direction (Tilt) With Fully 3D General Relativistic Magnetohydrodynamics Simulations (using HARM code)

3 M BH in M87 Optical+X-ray: 13kpc 300pc M~( )E9Msun (Gebhardt & Thomas 2009) D~16Mpc Lbol/Ledd~1E-6 Lbol/(Mdot c 2 )~1E-2 Optical: 1kpc VLBI Radio: 1kpc 0.06pc Junor (1999) Biretta (1999,2002) VLBA Radio: 0.1pc 0.01pc : Walker et al. (2008)

4 Earth-Wide VLBI shows M87 correlated flux size ~ 5.5rs Doeleman et al. (2012, Science) Vincent Fish (Thurs. 11:35am) Hada et al. (2011, Nature) 2Ghz to 43Ghz 1.3mm = 230 Ghz

5 Constraint of Spin in M87? Doeleman et al. (2012, Science) ISCO ISCO z 5.5rs 3 sigma 1sigma But ISCO = Inner-Most Stable Circular Orbit ISCO important for thin Keplerian disks but not for thick radiatively inefficient flows (RIAFs) as in M87

6 a = -0.9 and a = +0.9 Jets are similar size! a= -0.9 : eff~35% ISCO=8.7M a=+0.9 : eff~100% ISCO=2.3M GRMHD Simulations (Jet = where most power is) So, ISCO might not work as jet base size for M87 (Tchekhovskoy & McKinney 2012)

7 Role of Magnetic Field / Flux Weak Field MRI Disk + Blandford-Znajek Jet = Flux is Fine-Tuned Saturated Field MAD Disk + Blandford-Znajek Jet = Flux in Force Balance z z R MRI = Magneto-Rotational Instability Blandford & Znajek (77) MacDonald & Thorne (82), Balbus & Hawley (1991,1998) MAD = Magnetically Arrested Disk Znajek (76), Bisnovatyi-Kogan & Ruzmaikin (74,76), Narayan et al. (03), Reynolds et al. (06), Igumenshchev et al. (03)

8 How much Magnetic Flux? Coherent Flux near Galactic Nucleus or in ISM: or greater Magnetospheric Radius (McKinney, Tchekhovskoy, Blandford 2012): 1) Mass Flux Bz 2) Ram/Gravity vs. Field 3) Solve for Bz 4) Integrate Bz out to r m R m 5) Solve for r m ( ) SgrA* : r m >10 7 r g M87 : r m > 10 2 r g

9 Role of Magnetic Flux Accumulation Physical Setup: Spin: a=0.99 (+-0.9,0.5,0.2,0.1,0) Radiatively Inefficient Thick Extended-R Disk Run: ~30,000M Numerical Setup: Fully 3D (no syms) Kerr-Schild Coords 288x128x x128x256 Large outer radius Explicit Res+Conv Tests Tchekhovskoy, Narayan, McKinney (2011) McKinney, Tchekhovskoy, Blandford (2012)

10 Magnetically Choked Accretion Flow Mass Accretion Rate BH & Jet Dimensionless Magnetic Flux BH & Jet Efficiency 30 Years for M87

11 Magnetically Choked Accretion Flow Time-Azimuthal Average: Red: Magnetic Field Lines Gray: Velocity Stream Lines Blue: Disk-Jet Boundary Green: Outflow Black: Unbound Outflow Magnetic Flux Accumulates up to Natural Limit Force Balance between Ram/Gravity and Magnetic Flux MRI (magneto-rotational/balbus-hawley instability) suppressed! Igumenshchev et al. (08,09), Tchekhovskoy et al. (11,12), McKinney et al. (12)

12 Black Hole Tilt Frame-dragging force -> Lense-Thirring Precession -> Disk warp Lamb et al. Why Care? Affects: BH Spin Evolution Photon Spectra Variability and QPOs Jet direction? Resolved Image

13 Black Hole Tilt [15deg] Weak Magnetic Field and MHD Turbulence Lense-Thirring Precession No Jet, no Bardeen- Petterson Alignment Precession just set by outer disk extent Fragile et al (Danilo Teixeira Wed, 3:12pm)

14 GR-MHD with Tilt Physical Setup: Spin: a=0.99 (+-0.94,0.9,0) Radiatively Inefficient Thick Extended-R Disk (H/R=0.3,0.6) Run: ~30,000M Tilt: 0.1,0.3,0.6,0.7rad, 90deg (Tilt turned on mid-way) McKinney, Tchekhovskoy, Blandford (2012, Science Mag. Express Nov 15) Numerical Setup: Fully 3D (no syms.) Kerr-Schild Coords. 288x128x x128x256 Large outer radius

15 Black Hole Tilt [0deg -> 90deg] Naturally Saturated Magnetic Field Strength Jet Controls Disk

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18 Some Effects of BH Tilt Bardeen-Petterson effect (LT=Lense-Thirring) for thin disks Magneto-spin mechanism for thick disks with jets (Can derive magneto-spin radius and EM>LT radius) Disk Warps & Jet Bends near Horizon (Impacts EHT interpretations of SgrA* & M87) Blazar zone where disk & jet interact (New dissipation mechanism) No precession for EM forces, unlike LT: TDEs, GRBs, etc. (Gezari, Kesden (Mon 3:12pm), Dai (Mon 2:36pm) & Nakar talks)

19 Old Disk & Jet Theory Disk with weak Jet (Fat Dog with tiny Tail) Weak Magnetic Fields Amplified by MRI Lense-Thirring with viscosity dominates New Disk & Jet Theory Jet can dominate Disk (Dog Chasing Tail) Magnetic Flux Naturally Accumulates Electromagnetic fields can dominate Gravity