Mapping the Dynamics of a Giant Ly-alpha Halo at z=4.1 with MUSE: The
  Energetics of a Large Scale AGN-Driven Outflow around a Massive,
  High-Redshift Galaxy
  We present deep MUSE integral-field unit (IFU) spectroscopic observations of
the giant (~150 x 80 kpc) Ly-alpha halo around the z=4.1 radio galaxy TNJ
J1338-1942. This 9-hr observation maps the two-dimensional kinematics of the
Ly-alpha emission across the halo. We identify two HI absorbers which are seen
against the Ly-alpha emission, both of which cover the full 150 x 80 kpc extent
of the halo and so have covering fractions ~1. The stronger and more
blue-shifted absorber (dv~1200 km/s) has dynamics that mirror that of the
underlying halo emission and we suggest that this high column material (n(HI) ~
10^19.4 /cm^2), which is also seen in CIV absorption, represents an out-flowing
shell that has been driven by the AGN (or star formation) within the galaxy.
The weaker (n(HI)~10^14 /cm^2) and less blue shifted (dv~500 km/s) absorber
most likely represents material in the cavity between the out-flowing shell and
the Ly-alpha halo. We estimate that the mass in the shell must be of order
10^10 Msol -- a significant fraction of the ISM from a galaxy at z=4. The large
scales of these coherent structures illustrate the potentially powerful
influence of AGN feedback on the distribution and energetics of material in
their surroundings. Indeed, the discovery of high-velocity (~1000 km/s),
group-halo-scale (i.e. >150 kpc) and mass-loaded winds in the vicinity of the
central radio source are broadly in agreement with the requirements of models
that invoke AGN-driven outflows to regulate star formation and black-hole
growth in massive galaxies at early times.
