Dissecting the complex environment of a distant quasar with MUSE
  High redshift quasars can be used to trace the early growth of massive
galaxies and may be triggered by galaxy-galaxy interactions. We present MUSE
science verification data on one such interacting system consisting of the
well-studied z=3.2 PKS1614+051 quasar, its AGN companion galaxy and bridge of
material radiating in Lyalpha between the quasar and its companion. We find a
total of four companion galaxies (at least two galaxies are new discoveries),
three of which reside within the likely virial radius of the quasar host,
suggesting that the system will evolve into a massive elliptical galaxy by the
present day. The MUSE data are of sufficient quality to split the extended
Lyalpha emission line into narrow velocity channels. In these the gas can be
seen extending towards each of the three neighbouring galaxies suggesting that
the emission-line gas originates in a gravitational interaction between the
galaxies and the quasar host. The photoionization source of this gas is less
clear but is probably dominated by the two AGN. The quasar's Lyalpha emission
spectrum is double-peaked, likely due to absorbing neutral material at the
quasar's systemic redshift with a low column density as no damping wings are
present. The spectral profiles of the AGN and bridge's Lyalpha emission are
also consistent with absorption at the same redshift indicating this neutral
material may extend over > 50 kpc. The fact that the neutral material is seen
in the line of sight to the quasar and transverse to it, and the fact that we
see the quasar and it also illuminates the emission-line bridge, suggests the
quasar radiates isotropically and any obscuring torus is small. These results
demonstrate the power of MUSE for investigating the dynamics of interacting
systems at high redshift.
