The most powerful quasar outflows as revealed by the C IV λ 1549 resonance line

Outflows from quasars may be almost ubiqui-tous, but there are significant differences on a source- by-source basis. These differences can be organized along the 4D Eigenvector 1 sequence: at low z, only the Population A sources radiating at relatively high Eddington ratio show evidences of prominent high- velocity outflows from the Civ λ 1549 line profiles. Here we discuss, starting from recent observations of high-luminosity sample of Hamburg-ESO quasars, the Civ λ 1549 emission line profiles and how they are affected by outflow motion as a function of the quasar luminosity. Our high-luminosity sample has the no-table advantage that the rest frame has been set by previous H β observations in the J, H, and K band, therefore making measurements of inter-line shift accurate and free of systemic biases. As the redshift increases and the luminosity of the brightest quasars grows, powerful, high-velocity outflows may become more frequent. We then discuss the outflow contextualisation following the 4DE1 approach as a tool for unveiling the nature of the so-called Weak Lined Quasars (WLQs) that have emerged in recent years as a new, poorly understood class of quasars. We estimate the kinetic