A coronagraphic absorbing cloud reveals the narrow-line region and
  extended Lyman-$\alpha$ emission of QSO J0823+0529
  We report long-slit spectroscopic observations of the quasar SDSS
J082303.22+052907.6 ($z_{\rm CIV}$$\sim$3.1875), whose Broad Line Region (BLR)
is partly eclipsed by a strong damped Lyman-$\alpha$ (DLA; log$N$(HI)=21.7)
cloud. This allows us to study the Narrow Line Region (NLR) of the quasar and
the Lyman-$\alpha$ emission from the host galaxy. Using CLOUDY models that
explain the presence of strong NV and PV absorption together with the detection
of SiII$^*$ and OI$^{**}$ absorption in the DLA, we show that the density and
the distance of the cloud to the quasar are in the ranges 180 $<$ $n_{\rm H}$
$<$ 710 cm$^{-3}$ and 580 $>$ $r_0$ $>$230 pc, respectively. Sizes of the
neutral($\sim$2-9pc) and highly ionized phases ($\sim$3-80pc) are consistent
with the partial coverage of the CIV broad line region by the CIV absorption
from the DLA (covering factor of $\sim$0.85). We show that the residuals are
consistent with emission from the NLR with CIV/Lyman-$\alpha$ ratios varying
from 0 to 0.29 through the profile. Remarkably, we detect extended
Lyman-$\alpha$ emission up to 25kpc to the North and West directions and 15kpc
to the South and East. We interpret the emission as the superposition of strong
emission in the plane of the galaxy up to 10kpc with emission in a wind of
projected velocity $\sim$500kms$^{-1}$ which is seen up to 25kpc. The low
metallicity of the DLA (0.27 solar) argues for at least part of this gas being
in-falling towards the AGN and possibly being located where accretion from cold
streams ends up.
