Radiative Models of Sgr A* and M87* from Relativistic MHD Simulations Jason Dexter University of Washington / UC Berkeley With Eric Agol, Chris Fragile and Jonathan McKinney

Sagittarius A* AHAR 2011: The Central Kiloparsec2 Jet or nonthermal electrons far from BH Thermal electrons at BH Simultaneous IR/X-ray flares close to BH? no data available Charles Gammie, Rainer Schödel

Millimeter VLBI of Sgr A* Precision black hole astrophysics 3AHAR 2011: The Central Kiloparsec Doeleman et al. (2008) Gaussian FWHM ~4 R s !

Black Hole Images & Shadows Sensitive to viewing geometry & details of accretion flow – Need accurate theoretical predictions! Bardeen (1973); Dexter & Agol (2009) Falcke, Melia & Agol (2000) 4AHAR 2011: The Central Kiloparsec Broderick & Loeb (2009) Dexter et al. (2009, 2010)

Models of Sgr A* Semi-analytic: – RIAF or jet Narayan & Yi (1995), Yuan et al. (2003), Broderick et al. (2009, 2010, 2011), Falcke & Markoff (2000) – Hotspots/expanding blobs Broderick & Loeb (2006), Eckart et al. (2006), Yusef-Zadeh et al. (2006) MHD Simulations: – Non-relativistic Goldston et al. (2005), Chan et al. (2008), Huang et al. (2009) – Axisymmetric or averaged GRMHD Noble et al. (2007), Moscibrodzka et al. (2009), Hilburn et al. (2009) AHAR 2011: The Central Kiloparsec5

GRMHD Models of Sgr A* 3D, time-dependent GRMHD great for mm Sgr A* – Thick, MRI-driven accretion flow – Insignificant cooling(?) – Synchrotron radiation near BH Not perfect… – Collisionless plasma (mfp = 10 4 R s ) – No electrons Assume constant T i /T e AHAR 2011: The Central Kiloparsec6 Moscibrodzka et al. (2009)

Assume light rays are geodesics: –geokerr, Dexter & Agol (2009) 5 (4) Simulations: – Fragile et al. (2007, 2009) – McKinney & Blandford (2009) Synchrotron emissivity: – Leung et al. (2011) Joint fits to spectral & VLBI data: – Marrone 2006, Doeleman et al. 2008, Fish et al – Parameters: dM/dt, i, a, T i /T e AHAR 2011: The Central Kiloparsec7 Ray Tracing  Schnittman et al. (2006)

Parameter Estimates i = 60 degrees ξ = -70 degrees T e /10 10 K = 6 ± 2 dM/dt = 3 x M sun yr -1 All to 90% confidence AHAR 2011: The Central Kiloparsec Dexter et al. (2010, 2011) Sky Orientation Inclination Electron Temperature Accretion Rate All VLBI 2007

Millimeter Flares Correlation with accretion rate Driven by magnetic turbulence Models reproduce observed mm flares IR/X-ray? AHAR 2011: The Central Kiloparsec9 Solid – 230 GHz (1.3mm) Dotted – 690 GHz (0.4mm)

Black Hole Shadow in Sgr A* AHAR 2011: The Central Kiloparsec10 Shadow may be detected on Chile-Mexico baseline (in closure phase too) Shadow 230 GHz 345 GHz

M M Sgr A* at 2000 D Sgr A* Jet launching physics? Known viewing geometry? AHAR 2011: The Central Kiloparsec11 7mm Junor et al. (1999) 2cm Kovalev et al. (2007) Hubble

M87* Models Simulation: McKinney & Blandford (2009) Jet: B 2 > ρc 2, u jet =ηB 2 Representative models: Disk/jet or jet Unlike previous models – Can’t have disk peak in radio – Can’t match radio at all AHAR 2011: The Central Kiloparsec12 Broderick & Loeb ( 2009)

Images & Visibilities Images are still crescents! Gaussian size: μas Shadow on Hawaii-Mexico or Mexico-Chile AHAR 2011: The Central Kiloparsec13 Dexter et al. (2011)

Conclusions Millimeter images/light curves of Sgr A* and M87* from GRMHD simulations Sgr A* (Dexter et al. 2009, 2010, 2011) – Excellent fits with GRMHD & images are crescents! – Estimates for viewing geometry and physical conditions – Reproduce observed mm flares – Mexico—Chile next best chance for observing shadow M87 (Dexter et al. 2011) – Disk/jet or jet models – Predict μas size, shadow on Hawaii—Chile or Mexico—Chile – Robust results if geometry is correct AHAR 2011: The Central Kiloparsec14

Tilted Sgr A* AHAR 2011: The Central Kiloparsec15 No reason to expect Sgr A* isn’t tilted Unconstrained parameters Best fit images are still crescents Shadow still visible Shadow

RIAF Fits AHAR 2011: The Central Kiloparsec16 Dexter et al. (2010, 2011), Broderick et al. (2010)

Shadow in Closure Phase AHAR 2011: The Central Kiloparsec17

Visibility Variance AHAR 2011: The Central Kiloparsec18

Spectra AHAR 2011: The Central Kiloparsec19

Accretion Rate Variability AHAR 2011: The Central Kiloparsec20

Event Horizon Telescope AHAR 2011: The Central Kiloparsec21 UV coverage (Phase I: black) From Shep Doeleman’s Decadal Survey Report on the EHT Doeleman et al (2009)

Comparison to Observed Flares AHAR 2011: The Central Kiloparsec22 Eckart et al. (2008)Marrone et al. (2008)

Galactic Center Black Hole AHAR 2011: The Central Kiloparsec23