Quasar feedback and the origin of radio emission in radio-quiet quasars
  We conduct kinematic analysis of the SDSS spectra of 568 obscured luminous
quasars, with the emphasis on the kinematic structure of the [OIII]5007
emission line. [OIII] emission tends to show blueshifts and blue excess, which
indicates that at least part of the narrow-line gas is undergoing an organized
outflow. The velocity width containing 90% of line power ranges from 370 to
4780 km/sec, suggesting outflow velocities up to 2000 km/sec. The velocity
width of the [OIII] emission is positively 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 nu L_nu[1.4GHz] = 10^40 erg/sec suggests a median kinetic luminosity of the
quasar-driven wind of L_wind=3x10^44 erg/sec, or about 4% of the estimated
median bolometric luminosity L_bol=8x10^45 erg/sec. 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. As the outflow velocity increases, some emission lines characteristic
of shocks in quasi-neutral medium increase as well, which we take as further
evidence of quasar-driven winds propagating into the interstellar medium of the
host galaxy. None of the kinematic components show correlations with the
stellar velocity dispersions of the host galaxies, so there is no evidence that
any of the gas in the narrow-line region of quasars is in dynamical equilibrium
with the host galaxy. Quasar feedback appears to operate above the threshold
luminosity of L_bol=3x10^45 erg/sec.
