Oral Presentation

A look through the Rotation Measure in M87

Author(s): Juan-Carlos Algaba, Keiichi Asada, Masanori Nakamura, Cheng-Yu Kuo

Presenter: Juan Carlos Algaba (Korea Astronomy and Space Science Institute)

We investigate the distribution of Faraday rotation measure (RM) in the M87 jet at arc-second scales by using archival polarimetric VLA data at 8, 15, 22 and 43 GHz. We resolve the structure of the RM and derive the power spectrum in the arcsecond scale jet, finding indications that the RM cannot be associated with a turbulent magnetic field with 3D Kolmogorov spectrum. Our analysis indicates that the RM probed on jet scales has a significant contribution of a Faraday screen associated with the vicinity of the jet, in contrast with that on kilo parsec scales, typically assumed to be disconnected from the jet. Additionally, we investigate the sub-mm RM in the core regions of M87 with the SMA to constrain the mass accretion rate to be below 9.2x10^(-4) M_sun/yr. This value is two orders of magnitude smaller than the Bondi accretion rate, favouring ADIOS or CDAF type accretion models for M87.