The obstructed jet in Mrk 231

TL;DR

This study investigates the sub-relativistic, bent jet in Mrk 231, revealing its interaction with the interstellar medium and implications for AGN feedback and galaxy evolution.

Contribution

It provides the first detailed analysis of the jet's speed, structure, and environmental interactions in Mrk 231, highlighting jet obstruction effects.

Findings

Jet head speed estimated at ≤0.013c

Jet exhibits a change in position angle from -113° to -172°

Jet interacts with interstellar medium, creating wide-angle shocks

Abstract

Mrk~231 is the closest radio-quiet quasar known and one of the most luminous infrared galaxies in the local Universe. It is characterised by the co-existence of a radio jet and powerful multi-phase multi-scale outflows, making it an ideal laboratory to study active galactic nucleus (AGN) feedback. We analyse the multi-epoch very long baseline interferometry data of Mrk~231 and estimate the jet head advance speed to be $\lesssim0.013\ c$, suggesting a sub-relativistic jet flow. The jet position angle changes from $-113^\circ$ in the inner parsec to $-172^\circ$ at a projected distance of 25 parsec. The jet structure change might result from either a jet bending following the rotation of the circum-nuclear disc or the projection of a helical jet on the plane of the sky. In the large opening angle ($\sim60^\circ$) cone, the curved jet interacts with the interstellar medium and creates wide-aperture-angle shocks which subsequently dissipate a large portion of the jet power through radiation and contribute to powering the large-scale outflows. The low power and bent structure of the Mrk~231 jet, as well as extensive radiation dissipation, are consistent with the obstruction of the short-length jet by the host galaxy's environment.