The obstructed jet in Mrk 231
  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.
