First detection of 350 micron polarization from a radio-loud AGN

Sang-Sung Lee, Seincheol Kang, Do-Young Byun, Nicholas Chapman, Giles Novak, Sascha Trippe, Juan Carlos Algaba, Motoki Kino

Published 2015-07-13Version 1

We report the first detection of linearly polarized emission at an observing wavelength of 350~$\mu$m from the radio-loud Active Galactic Nucleus (AGN) 3C~279. We conducted polarization observations for 3C~279 using the SHARP polarimeter in the Caltech Submillimeter Observatory (CSO) on 2014 March 13 and 14. For the first time, we detected the linear polarization with the degree of polarization of 13.3\%$\pm$3.4\% {\bf($3.9\sigma$)} and the Electric Vector Position Angle (EVPA) of 34.7$^\circ\pm5.6^\circ$. We also observed 3C~279 simultaneously at 22, 43, and 86~GHz in dual polarization with the Korean VLBI Network (KVN) on 2014 March 6 (single dish) and imaged in milliarcsecond (mas) scales at 22, 43, 86, and 129~GHz on March 22 (VLBI). We found that the degree of linear polarization increases from 10\% to 13\% at 22~GHz to 350~$\mu$m and the EVPAs at all observing frequencies are parallel within $<10^\circ$ to the direction of the jet at mas scale, implying that the integrated magnetic fields are perpendicular to the jet in the innermost regions. We also found that the Faraday rotation measures RM are in a range of $-6.5\times10^2 \sim -2.7\times10^3$~rad~m$^{-2}$ between 22-86~GHz, and are scaled as a function of wavelength: $|{\rm RM}|\propto\lambda^{-2.2}$. These results indicate that the mm and sub-mm polarization emission are generated in the compact jet within 1~mas scale and affected by a Faraday screen in or in the close proximity of the jet.