Linear and Circular Polarization from Sagittarius A*

Geoffrey C. Bower1

1 UC Berkeley

E-mail contact: gbower@astro.berkeley.edu

see: ApJ, 521, 582 (1999); ApJL, 523, L29 (1999); ApJ, 527, 851 (1999); ApJL 555, L103 (2001); ApJ, 571, 843 (2002)

Sagittarius A* displays unique polarization properties which permit us to characterize the accretion and outflow conditions as well as probe the surrounding environment. The polarization differs substantially from that seen in powerful extragalactic radio sources. At centimeter wavelengths, Sgr A* shows no linear polarization but strong and variable circular polarization. At millimeter wavelengths, Sgr A* exhibits a sharp increase in the linear polarization while circular polarization is undetected. We discuss in detail new 1.3 millimeter wavelength polarimetry performed with the BIMA array that confirms the presence of linear polarization and determines a very low RM, < 2 x 10^6 rad m^-2. These measurements place strong constraints on models of accretion and outflow.