The MUSE 3D view of feedback in a high-metallicity radio galaxy at z =
  2.9
  We present a detailed study of the kinematic, chemical and excitation
properties of the giant Ly$\alpha$ emitting nebula and the giant \ion{H}{I}
absorber associated with the $z = 2.92$ radio galaxy MRC 0943--242, using
spectroscopic observations from VLT/MUSE, VLT/X-SHOOTER and other instruments.
Together, these data provide a wide range of rest-frame wavelength (765 \AA$\,$
-- 6378 \AA$\,$ at $z = 2.92$) and 2D spatial information. We find clear
evidence for jet gas interactions affecting the kinematic properties of the
nebula, with evidence for both outflows and inflows being induced by radio-mode
feedback. We suggest that the regions of relatively lower ionization level,
spatially correlated with the radio hotspots, may be due to localised
compression of photoionized gas by the expanding radio source, thereby lowering
the ionization parameter, or due to a contribution from shock-heating. We find
that photoionization of super-solar metallicity gas ($Z/Z_{\odot}$ = 2.1) by an
AGN-like continuum ($\alpha$=--1.0) at a moderate ionization parameter ($U$ =
0.018) gives the best overall fit to the complete X-SHOOTER emission line
spectrum. We identify a strong degeneracy between column density and Doppler
parameter such that it is possible to obtain a reasonable fit to the \ion{H}{I}
absorption feature across the range log N(\ion{H}{I}/cm$^{-2}$) = 15.20 and
19.63, with the two best-fitting occurring near the extreme ends of this range.
The extended \ion{H}{I} absorber is blueshifted relative to the emission line
gas, but shows a systematic decrease in blueshift towards larger radii,
consistent with a large scale expanding shell.
