Survey of Extremely High-velocity Outflows in Sloan Digital Sky Survey Quasars

TL;DR

This survey identifies and characterizes extremely high-velocity outflows in quasars using SDSS data, revealing their potential significance in quasar feedback and evolution, with larger kinetic power than previously known outflows.

Contribution

It is the first large-scale survey of EHVO quasars in SDSS, expanding the known sample by an order of magnitude and analyzing their properties and implications for quasar physics.

Findings

40 EHVO quasars identified, ten times more than previous studies.

EHVO quasars lack HeII emission and have higher bolometric luminosities and black hole masses.

Outflows' kinetic power may rival or exceed that of BALQSO outflows.

Abstract

We present a survey of extremely high-velocity outflows (EHVOs) in quasars, defined by speeds between 0.1c and 0.2c. This region of the 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 CIV absorption, 10 times more than the number of previously known cases. We characterize the EHVO absorption and find that in 26 cases, CIV is accompanied by NV and/or OVI absorption. We find that EHVO quasars lack HeII emission and have overall larger bolometric luminosities and black hole masses than those of their parent sample and 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 Lbol and lack of HeII 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.