Astronomy and Astrophysics – Astrophysics
Scientific paper
2007-02-02
JCAP 0703:011,2007
Astronomy and Astrophysics
Astrophysics
6 pages, 1 figure, accepted for publication in JCAP (Journal of Cosmology & Astroparticle Physics)
Scientific paper
10.1088/1475-7516/2007/03/011
We show that the radial profiles of the temperature and density of the electrons as well as the magnetic field strength around the massive black hole at the Galactic center, SgrA*, may be constrained directly from existing radio data without any need to make prior assumptions about the dynamics of the emitting gas. The observed spectrum and wavelength-dependent angular size of SgrA* indicate that the synchrotron emission originates from an optically-thick plasma of quasi-thermal electrons. We find that the electron temperature rises above the virial temperature within tens of Schwarzschild radii from the black hole, suggesting that the emitting plasma may be outflowing. Constraints on the electron density profile are derived from polarization measurements. Our best-fit results differ from expectations based on existing theoretical models. However, these models cannot be ruled out as of yet due to uncertainties in the source size measurements. Our constraints could tighten considerably with future improvements in the size determination and simultaneous polarization measurements at multiple wavelengths.
Loeb Abraham
Waxman Eli
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