2020ApJ...896..151R

We present a survey of extremely high-velocity outflows (EHVOs) in quasars, defined by speeds between 0.1c and 0.2c. This region of parameter space has not been included in previous surveys, but it might present the biggest challenge for theoretical models and it might be a large contributor to feedback due to the outflows' potentially large kinetic power. Using the Sloan Digital Sky Survey, we find 40 quasar spectra with broad EHVO C IV absorption, 10 times more than the number of previously known cases. We characterize the EHVO absorption and find that in 26 cases, C IV is accompanied by N V and/or O VI absorption. We find that EHVO quasars lack He II emission and have overall larger bolometric luminosities and black hole masses than those of their parent sample and broad absorption line quasars (BALQSOs), while we do not find significant differences in their Eddington ratios. We also report a trend toward larger black hole masses as the velocity of the outflowing gas increases in the BALQSOs in our sample. The overall larger L_bol and lack of He II emission of EHVO quasars suggest that radiation is likely driving these outflows. We find a potential evolutionary effect as EHVO quasars seem to be more predominant at large redshifts. We estimate that the kinetic power of these outflows may be similar to or even larger than that of the outflows from BALQSOs as the velocity factor increases this parameter by 1-2.5 orders of magnitude. Further study of EHVO quasars will help improve our understanding of quasar physics.