Polarized Emission of Sagittarius A*

doi:10.1088/0004-637X/703/1/557

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Lei Huang et al. 2009 ApJ 703 557 doi:10.1088/0004-637X/703/1/557

POLARIZED EMISSION OF SAGITTARIUS A*

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Lei Huang^1,2,3, Siming Liu⁴, Zhi-Qiang Shen², Ye-Fei Yuan¹, Mike J. Cai³, Hui Li⁵ and Christopher L. Fryer^5,6

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mlhuang@ustc.edu.cn yfyuan@ustc.edu.cn zshen@shao.ac.cn mike@asiaa.sinica.edu.tw sliu@astro.gla.ac.uk hli@lanl.gov fryer@lanl.gov

¹ Key Laboratory for Research in Galaxies and Cosmology, The University of Sciences and Technology of China, Chinese Academy of Sciences, Hefei 230026, China
² Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai 200030, China
³ Academia Sinica, Institute of Astronomy and Astrophysics, Taipei 106, Taiwan
⁴ Department of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ, UK
⁵ Los Alamos National Laboratory, Los Alamos, NM 87545, USA
⁶ Physics Department, The University of Arizona, Tucson, AZ 85721, USA

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Abstract References Cited By

We explore the parameter space of the two-temperature pseudo-Newtonian Keplerian accretion flow model for the millimeter and shorter wavelength emission from Sagittarius A*. A general relativistic (GR) ray-tracing code is used to treat the radiative transfer of polarized synchrotron emission from the flow. The synchrotron self-Comptonization and bremsstrahlung emission components are also included. It is shown that the model can readily account for the millimeter to submillimeter emission characteristics with an accretion rate of ~6 × 10¹⁷ g s^–1 and an inclination angle of ~40°. However, the corresponding model-predicted near-infrared (NIR) and X-ray fluxes are more than one order of magnitude lower than the observed "quiescent" state values. While the extended quiescent-state X-ray emission has been attributed to thermal emission from the large-scale accretion flow, the NIR emission and flares are likely dominated by emission regions either within the last stable orbit of a Schwarzschild black hole or associated with outflows. With the viscous parameter derived from numerical simulations, there is still a degeneracy between the electron heating rate and the magnetic parameter. A fully GR treatment with the black hole spin incorporated will resolve these issues.

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