Kinematics and excitation of the nuclear spiral in the active galaxy Arp
  102B
  We present a two-dimensional analysis of the gaseous excitation and
kinematics of the inner 2.5 x 1.7 kpc^2 of the LINER/Seyfert 1 galaxy Arp 102B,
from optical spectra obtained with the GMOS integral field spectrograph on the
Gemini North telescope at a spatial resolution of 250 pc. Emission-line flux
maps show the same two-armed nuclear spiral we have discovered in previous
observations with the HST-ACS camera. One arm reaches 1 kpc to the east and the
other 500 pc to the west, with a 8.4 GHz VLA bent radio jet correlating with
the former. The gas density is highest (500 - 900 cm^(-3)) at the nucleus and
in the northern border of the east arm, at a region where the radio jet seems
to be deflected. Channel maps show blueshifts but also some redshifts at the
eastern arm and jet location which can be interpreted as originated in the
front and back walls of an outflow pushed by the radio jet, suggesting also
that the outflow is launched close to the plane of the sky. We estimate a mass
outflow rate along the east arm of 0.26 - 0.32 Msun yr^(-1) (depending on the
assumed outflow geometry), which is between one and two orders of magnitude
higher than the mass accretion rate to the active nucleus, implying that there
is mass-loading of the nuclear outflow from circumnuclear gas. The power of
this outflow is 0.06 - 0.3%Lbol. We propose a scenario in which gas has been
recently captured by Arp 102B in an interaction with Arp 102A, settling in a
disk rotating around the nucleus of Arp 102B and triggering its nuclear
activity. A nuclear jet is pushing the circumnuclear gas, giving origin to the
nuclear arms. A blueshifted emitting gas knot is observed at 300 pc south-east
from the nucleus and can be interpreted as another (more compact) outflow, with
a possible counterpart to the north-west.
