A persistent double nuclear structure in 3C 84

Abstract

3C 84 (NGC 1275) is the radio source at the centre of the Perseus cluster and exhibits a bright radio jet. We observed the source with the Global Millimeter VLBI Array (GMVA) between 2008 and 2015, with a typical angular resolution of similar to 50 mu as. The observations revealed a consistent double nuclear structure separated by similar to 770 gravitational radii assuming a black hole mass of 3.2 x 10(8) M-circle dot. The region is likely too broad and bright to be the true jet base anchored in the accretion disc or black hole ergosphere. A cone and parabola were fit to the stacked (time averaged) image of the nuclear region. The data did not strongly prefer either fit, but combined with a jet/counter-jet ratio analysis, an upper limit on the viewing angle to the inner jet region of <= 35 degrees was found. This provides evidence for a variation of the viewing angle along the jet (and therefore a bent jet) within similar to 0.5 pc of the jet launching region. In the case of a conical jet, the apex is located similar to 2400 gravitational radii upstream of the bright nuclear region and up to similar to 600 gravitational radii upstream in the parabolic case. We found a possible correlation between the brightness temperature and relative position angle of the double nuclear components, which may indicate rotation within the jet.