THE SUBMILLIMETER BUMP IN Sgr A* FROM RELATIVISTIC MHD SIMULATIONS

Journal Article · Sat Jul 10 00:00:00 EDT 2010 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/717/2/1092· OSTI ID:21455199

Dexter, Jason ^[1]; Agol, Eric ^[2]; Fragile, P Chris ^[3]

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1. Department of Physics, University of Washington, Seattle, WA 98195-1560 (United States)
2. Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States)
3. Department of Physics and Astronomy, College of Charleston, Charleston, SC 29424 (United States)

Recent high resolution observations of the Galactic center black hole allow for direct comparison with accretion disk simulations. We compare two-temperature synchrotron emission models from three-dimensional, general relativistic magnetohydrodynamic simulations to millimeter observations of Sgr A*. Fits to very long baseline interferometry and spectral index measurements disfavor the monochromatic face-on black hole shadow models from our previous work. Inclination angles {<=}20{sup 0} are ruled out to 3{sigma}. We estimate the inclination and position angles of the black hole, as well as the electron temperature of the accretion flow and the accretion rate, to be i=50{sup o+35o}{sub -15}{sup o}, {xi}=-23{sup o+97o}{sub -22}{sup o}, T{sub e} = (5.4 {+-} 3.0) x 10{sup 10} K, and M-dot =5{sup +15}{sub -2}x10{sup -9} M{sub sun} yr{sup -1}, respectively, with 90% confidence. The black hole shadow is unobscured in all best-fit models, and may be detected by observations on baselines between Chile and California, Arizona, or Mexico at 1.3 mm or .87 mm either through direct sampling of the visibility amplitude or using closure phase information. Millimeter flaring behavior consistent with the observations is present in all viable models and is caused by magnetic turbulence in the inner radii of the accretion flow. The variability at optically thin frequencies is strongly correlated with that in the accretion rate. The simulations provide a universal picture of the 1.3 mm emission region as a small region near the midplane in the inner radii of the accretion flow, which is roughly isothermal and has {nu}/{nu} {sub c} {approx} 1-20, where {nu} {sub c} is the critical frequency for thermal synchrotron emission.

• OSTI ID: 21455199
• Journal Information: Astrophysical Journal, Vol. 717, Issue 2; Other Information: DOI: 10.1088/0004-637X/717/2/1092; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ACCRETION DISKS
BLACK HOLES
CRITICAL FREQUENCY
ELECTRON TEMPERATURE
FLARING
GALAXIES
GALAXY NUCLEI
INCLINATION
INTERFEROMETRY
MAGNETOHYDRODYNAMICS
MONOCHROMATIC RADIATION
RELATIVISTIC RANGE
SIMULATION
THREE-DIMENSIONAL CALCULATIONS
TURBULENCE
ELECTROMAGNETIC RADIATION
ENERGY RANGE
FLUID MECHANICS
HYDRODYNAMICS
MECHANICS
RADIATIONS