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The Submillimeter Bump of Sgr A* from GRMHD Simulations

The Submillimeter Bump of Sgr A* from GRMHD Simulations. Jason Dexter University of Washington. With Eric Agol, Chris Fragile and Jon McKinney. Sub-mm Sgr A*. Doeleman et al (2008). . Precision black hole astrophysics Probe strong gravity!. ~4 R s !. Yuan et al (2003).

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The Submillimeter Bump of Sgr A* from GRMHD Simulations

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  1. The Submillimeter Bump ofSgr A* from GRMHD Simulations Jason Dexter University of Washington With Eric Agol, Chris Fragile and Jon McKinney

  2. Sub-mm Sgr A* Doeleman et al (2008)  • Precision black hole astrophysics • Probe strong gravity! ~4 Rs! Yuan et al (2003) Probing Strong Gravity

  3. Black Hole Shadow • Sensitive to details of accretion flow • 3D GRMHD! Bardeen (1973); Dexter & Agol (2009) Falcke, Melia & Agol (2000) Probing Strong Gravity

  4. Modeling • Geodesics from Dexter & Agol (2009) • Time-dependent, relativistic radiative transfer • Simulation from Fragile et al (2007) • Fit images to VLBI data over grid in Mtor, i, ξ, tobs • Unpolarized; single temperature Schnittman et al (2006) Probing Strong Gravity

  5. GRMHD Fits to VLBI Data i=10 degrees i=70 degrees Dexter, Agol & Fragile (2009); Doeleman et al (2008) 100 μas 10,000 km Probing Strong Gravity

  6. Improved Modeling • Sub-mm spectral index (Marrone 2006) • Add simulations from McKinney & Blandford (2009); Fragile et al (2009) • Two-temperature models (parameter Ti/Te) • Joint fits to spectral, VLBI data over grid in Mtor, i, a, Ti/Te • Angle-dependent emissivity (Leung et al 2010) Probing Strong Gravity

  7. Parameter Estimates +35 -15 • i = 50 degrees • Te /1010 K = 5.4±3.0 • ξ = -23 degrees • All to 90% confidence • Results agree with Broderick et al (2009) Inclination Spin +97 -22 Sky Orientation Electron Temperature Probing Strong Gravity

  8. Millimeter Flares • Models reproduce observed mm flare duration, amplitude, frequency • Strong correlation with accretion rate • Not caused by heating from magnetic reconnection Solid – 230 GHz Dotted – 690 GHz Probing Strong Gravity

  9. Shadow of Sgr A* Shadow may be detected on chile-lmt, smto-chile baselines; otherwise need south pole. Probing Strong Gravity

  10. Conclusions • Fit 3D GRMHD images/light curves of Sgr A* to mm observations • Estimates of inclination, sky orientation agree with RIAF fits (Broderick et al 2009) • Electron temperature well constrained • Reproduce observed mm flares • LMT-Chile next best chance for observing shadow • Future: polarized emission, tilted disks. Probing Strong Gravity

  11. Comparison to Observed Flares Marrone et al (2008) Eckart et al (2008) Probing Strong Gravity

  12. Spectra Probing Strong Gravity

  13. Visibility Variance Probing Strong Gravity

  14. Accretion Rate Variability Probing Strong Gravity

  15. RIAF Fits Broderick et al (2009) Probing Strong Gravity

  16. Event Horizon Telescope From Shep Doeleman’s Decadal Survey Report on the EHT UV coverage (Phase I: black) Doeleman et al (2009) Probing Strong Gravity

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