  Black hole feedback is now a standard component of galaxy formation models.
These models predict that the impact of black hole activity on its host galaxy
likely peaked at z=2-3, the epoch of strongest star formation activity and
black hole accretion activity in the Universe. We used XShooter on the Very
Large Telescope to measure rest-frame optical spectra of four z~2.5 extremely
red quasars with infrared luminosities ~10^47 erg/sec. We present the discovery
of very broad (full width at half max= 2600-5000 km/sec), strongly blue-shifted
(by up to 1500 km/sec) [OIII]5007A emission lines in these objects. In a large
sample of obscured and red quasars, [OIII] kinematics are positively correlated
with infrared luminosity, and the four objects in our sample are on the extreme
end both in [OIII] kinematics and infrared luminosity. We estimate that ~3% of
the bolometric luminosity in these objects is being converted into the kinetic
power of the observed wind. Photo-ionization estimates suggest that the [OIII]
emission might be extended on a few kpc scales, which would suggest that the
extreme outflow is affecting the entire host galaxy of the quasar. These
sources may be the signposts of the most extreme form of quasar feedback at the
peak epoch of galaxy formation, and may represent an active "blow-out" phase of
quasar evolution.
