Gas inflows in the polar ring of NGC 4111: the birth of an AGN
  We have used Hubble Space Telescope (HST) images, SAURON Integral Field
Spectroscopy (IFS) and adaptative optics assisted Gemini NIFS near-infrared
K-band IFS to map the stellar and gas distribution, excitation and kinematics
of the inner few kpc of the nearby edge-on S0 galaxy NGC 4111. The HST images
map its $\approx$ 450 pc diameter dusty polar ring, with an estimated gas mass
$\ge10^7$ M$_\odot$. The NIFS datacube maps the inner 110 pc radius at
$\approx$ 7 pc spatial resolution revealing a $\approx$ 220 pc diameter polar
ring in hot ($2267\pm166$ K) molecular H$_2$ 1-0 S(1) gas embedded in the polar
ring. The stellar velocity field shows disk-dominated kinematics along the
galaxy plane both in the SAURON large-scale and in the NIFS nuclear-scale data.
The large-scale [O III] $\lambda5007$ \AA velocity field shows a superposition
of two disk kinematics: one similar to that of the stars and another along the
polar ring, showing non-circular motions that seem to connect with the velocity
field of the nuclear H$_2$ ring, whose kinematics indicate accelerated inflow
to the nucleus. The estimated mass inflow rate is enough not only to feed an
Active Galactic Nucleus (AGN) but also to trigger circumnuclear star formation
in the near future. We propose a scenario in which gas from the polar ring,
which probably originated from the capture of a dwarf galaxy, is moving inwards
and triggering an AGN, as supported by the local X-ray emission, which seems to
be the source of the H$_2$ 1-0 S(1) excitation. The fact that we see neither
near-UV nor Br$\gamma$ emission suggests that the nascent AGN is still deeply
buried under the optically thick dust of the polar ring.
