Probing the Parsec-scale Accretion Flow of 3C 84 with Millimeter
  Polarimetry
  We report the discovery of Faraday rotation toward radio source 3C 84, the
active galactic nucleus in NGC1275 at the core of the Perseus Cluster. The
rotation measure (RM), determined from polarization observations at wavelengths
of 1.3 and 0.9 mm, is (8.7 +/- 2.3) x 10^5 radians/m^2, among the largest ever
measured. The RM remained relatively constant over a 2 year period even as the
intrinsic polarization position angle wrapped through a span of 300 degrees.
The Faraday rotation is likely to originate either in the boundary layer of the
radio jet from the nucleus, or in the accretion flow onto the central black
hole. The accretion flow probably is disk-like rather than spherical on scales
of less than a parsec, otherwise the RM would be even larger.
