The recurrent nuclear activity of Fornax A and its interaction with the cold gas

TL;DR

This study uses high-resolution MeerKAT radio observations to reveal that Fornax A's nuclear activity has been recurrent, with multiple episodes shaping its lobes and jets, and interacting with surrounding cold gas.

Contribution

It provides new insights into the recurrent nature of Fornax A's nuclear activity and its interaction with cold gas using detailed radio and gas kinematic data.

Findings

Fornax A's lobes have a double-shell morphology with embedded filaments.

The last nuclear activity episode ceased about 12 Myr ago.

Recent activity (~3 Myr ago) produced central jets.

Abstract

Sensitive (noise $\sim 16\,\mu$\Jyb), high-resolution ($\sim 10''$) MeerKAT observations of Fornax A show that its giant lobes have a double-shell morphology, where dense filaments are embedded in a diffuse and extended cocoon, while the central radio jets are confined within the host galaxy. The spectral radio properties of the lobes and jets of Fornax A reveal that its nuclear activity is rapidly flickering. Multiple episodes of nuclear activity must have formed the radio lobes, for which the last stopped $12$ Myr ago. More recently ($\sim 3$ Myr ago), a less powerful and short ($\lesssim 1$ Myr) phase of nuclear activity generated the central jets. The distribution and kinematics of the neutral and molecular gas in the centre give insights on the interaction between the recurrent nuclear activity and the surrounding interstellar medium.