The most powerful quasar outflows as revealed by the Civ {\lambda}1549
  resonance line
  While quasar outflows may be quasi-ubiquitous, there are significant
differences on a source-by- source basis. These differences can be organized
along the 4D Eigenvector 1 sequence: at least at low z, with only Population A
sources radiating at relatively high Eddington ratio and showing prominent
high-velocity outflows in Civ {\lambda}1549 line profiles. We discuss in this
paper VLT-FORS observations of Civ {\lambda}1549 emission line profiles for a
high-luminosity sample of Hamburg- ESO quasars and how they are affected by
outflow motion as a function of quasar luminosity. Our high- luminosity sample
has the notable advantage that the rest frame has been accurately determined
from previous VLT-ISAAC observations of H{\beta} in the J, H, and K bands. This
makes measures of inter-line velocity shifts accurate and free of systemic
biases. As the redshift increases and the luminosity of the brightest quasars
increases, powerful, high-velocity outflows become more frequent. We discuss
the outflow contextualisation, fol- lowing the 4DE1 formalism, as a tool for
understanding the nature of the so-called weak lined quasars (WLQ) discovered
in recent years as a new, poorly understood class of quasars. We estimate the
kinetic power associ- ated with Civ {\lambda}1549 outflows and suggest that the
host galaxies in the most luminous sources likely experience significant
feedback.
