2014MNRAS.442..784Z

We analyse Sloan Digital Sky Survey spectra of 568 obscured luminous quasars. The [OIII] λ5007 Å emission line shows blueshifts and blue excess, indicating that some of the narrow-line gas is undergoing an organized outflow. The velocity width containing 90 percent of line power ranges from 370 to 4780 km/s, suggesting outflow velocities up to ∼ 2000 km/s, and is strongly correlated with the radio luminosity among the radio-quiet quasars. We propose that radio emission in radio-quiet quasars is due to relativistic particles accelerated in the shocks within the quasar-driven outflows; star formation in quasar hosts is insufficient to explain the observed radio emission. The median radio luminosity of the sample of νLν[1.4GHz] = 10⁴⁰erg/s suggests a median kinetic luminosity of the quasar-driven wind of Lwind = 3x10⁴⁴ erg/s, or about 4 percent of the estimated median bolometric luminosity Lbol = 8x10⁴⁵ erg/s. Furthermore, the velocity width of [OIII] is positively correlated with mid-infrared luminosity, which suggests that outflows are ultimately driven by the radiative output of the quasar. Emission lines characteristic of shocks in quasi-neutral medium increase with the velocity of the outflow, which we take as evidence of quasar-driven winds propagating into the interstellar medium of the host galaxy. Quasar feedback appears to operate above the threshold luminosity of Lbol ∼ 3x10⁴⁵ erg/s.