A persistent double nuclear structure in 3C 84

TL;DR

This study used high-resolution VLBI observations to reveal a persistent double nuclear structure in 3C 84, suggesting a bent jet with potential rotation near the jet launching region.

Contribution

First detailed VLBI imaging of 3C 84's nuclear region showing a stable double structure and constraining jet geometry and orientation.

Findings

Double nuclear structure separated by ~770 gravitational radii.

Evidence for a bent jet with a viewing angle ≤35°.

Possible rotation indicated by brightness temperature and position angle correlation.

Abstract

3C 84 (NGC 1275) is the radio source at the center 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 $\sim$50 $\mu$as. The observations revealed a consistent double nuclear structure separated by $\sim$770 gravitational radii assuming a Black Hole mass of 3.2 $\times 10^{8}$ $M_{\odot}$. The region is likely too broad and bright to be the true jet base anchored in the accretion disk 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 $\leq$35$^{\circ}$ was found. This provides evidence for a variation of the viewing angle along the jet (and therefore a bent jet) within $\sim$0.5 parsec of the jet launching region. In the case of a conical jet, the apex is located $\sim$2400 gravitational radii upstream of the bright nuclear region and up to $\sim$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.