B0707-359: a case study of change in AGN-black hole spin axis
  Structures of radio galaxies have the potential to reveal inconstancy in the
axis of the beams, which reflect the stability in the spin axis of the
supermassive black hole at the centre. We present radio observations of the
giant radio galaxy B0707-359 whose structure offers an interesting case study
of an AGN that may be exhibiting not only inconstancy in AGN output but also
inconstancy in direction of ejection axis. Its radio morphology shows evidence
for a restarting of the jets accompanied by an axis change. The observed
side-to-side asymmetries of this giant radio galaxy suggest that the new jets
are not in the plane of the sky. We infer that the hotspot advance velocities
are unusually large and of magnitude a few-tenths of the speed of light. The
dual-frequency radio images are consistent with a model where the beams from
the central engine ceased, creating a relic double radio source; this
interruption was accompanied by triggering of a movement of the axis of the
central engine at a rate of a few degrees Myr^-1. The closer location of the
giant radio galaxy axis to the host minor axis rather than the host major axis
is supportive of the restarting and axis-change model for the formation of the
double-double structure rather than the backflow model.
