0320060

One of the greatest controversies in the physics of AGN jets is whether the plasma is mainly composed of normal matter or e+/e- pairs. The investigators will address this question directly by observing the Seyfert-like radio galaxies 3C 120 and 3C 84 with the Integral SPI instrument each for 500 ks in an attempt to detectthe redshifted 511 keV e+/e- annihilation line. If the jet which interacts strongly with the thermal medium in each galaxy is mainly composed of a pair plasma the positrons entering the medium will thermalize and annihilate. The emission line resulting from the annihilations should be quite narrow < 4 keV. The line can be detected by INTEGRAL unless the positron-to-proton ratio in the jet is less than 0.25 in 3C 120 and 0.04 in 3C 84. [truncated! Please see actual data for full text]