Observing the Time Evolution of the Multi-Component Nucleus of 3C\,84

TL;DR

This study uses high-resolution VLBI observations to analyze the complex, multi-component nucleus of 3C 84, revealing a mildly relativistic east-west double structure and its evolution over time.

Contribution

It provides the first detailed tracking of the emergence and motion of a double nucleus in 3C 84 using multi-epoch VLBA imaging at 43 GHz.

Findings

The double nucleus is marginally resolved and exhibits an east-west separation speed of approximately 0.086c.

The observed speed persists over a de-projected distance of about 1900-9800 gravitational radii from the black hole.

The nucleus structure is more complex than predicted by current jet models, with components aligned orthogonally to the large-scale jet.

Abstract

The advent of global mm-band Very Long Baseline Interferometry (VLBI) in recent years has finally revealed the morphology of the base of the two most prominent nearby, bright, extragalactic radio jets in M\,87 and 3C\,84. The images are quite surprising considering the predictions of jet theory and current numerical modeling. The jet bases are extremely wide compared to expectations and the nucleus of 3C\,84 is very complicated. It appears as a double in 86\,GHz observations with 50\,$\mu$as resolution and a triple nucleus with 30\,$\mu$as resolution with space-based VLBI by RadioAstron at 22\,GHz. What is even odder is that the double and triple are arranged along an east-west line that is approximately orthogonal to the north-south large scale jet on 150\,$\mu$as $-$ 4\,mas scales. We explore the emergence of an (east-west) double nucleus in the lower resolution 43\,GHz Very Long Baseline Array (VLBA) imaging from August 2018 to April 2020. The double is marginally resolved. We exploit the east-west resolution associated with the longest baselines, $\sim 0.08$\,mas, to track a predominantly east-west separation speed of $\approx 0.086\pm 0.008$\,c. We estimate that the observed mildly relativistic speed persists over a de-projected distance of $\sim 1900-9800$ times the central, supermassive black hole, gravitational radius ($\sim 0.3-1.5$\,lt-yrs) from the point of origin.