SUBARU and e-Merlin observations of NGC3718. Diaries of an SMBH recoil?
  NGC3718 is a LINER $L1.9$ galaxy, lying at a distance of about $\sim 17.4$
Mpc away from earth and its similarities with NGC5128 often award it the name
"northern Centaurus A". We use high angular resolution ($\sim100$ mas) e-Merlin
radio and SUBARU NIR ($\sim170$ mas) data, to take a detailed view of the
processes taking place in its central region. In order to preserve some
objectivity in our interpretation, we combine our results with literature
values and findings from previous studies. Our NIR maps suggest, on one hand,
that towards the stellar bulge there are no large scale absorption phenomena
caused by the apparent dust lane and, on the other, that there is a significant
(local) contribution from hot ($\sim1000$ K) dust to the nuclear NIR emission.
The position where this takes place appears to be closer to the offset compact
radio emission from our e-Merlin $6$ cm map, lying offset by $\sim4.25$ pc from
the center of the underlying stellar bulge. The shape of the radio map suggests
the presence of one (or possibly two, forming an X-shape) bipolar structure(s)
$\sim1$ ($\sim0.6$) arcsec across, which combined with the balance between the
gas and the stellar velocity dispersions and the presence of hard X-ray
emission, point towards effects expected by AGN feedback. We also argue that
NGC3718 has a "core" in its surface brightness profile, despite the fact that
it is a gas-rich galaxy and we discuss its mixed photometric and spectroscopic
characteristics. The latter combined with the observed spatial and radio
offsets, the relative redshift between the broad and the narrow
$H{\mathrm{\alpha}}$ line, the limited star formation activity and AGN
feedback, strongly imply the existence of an SMBH recoil. Finally, we discuss a
possible interpretation, that could naturally incorporate all these findings
into one physically consistent picture.
