Radiative AGN feedback constraints from line-locked CIV winds in quasar spectra

Active galactic nuclei (AGN) feedback plays a fundamental role in regulating the evolution of galaxies, but the main driving processes and their contributions are still uncertain. We use  SDSS/BOSS DR16 quasar spectra containing absorption features from CIV in quasar outflows to investigate the presence of the radiation-pressure signature dubbed line-locking, and to infer wind properties from stacked samples. We design software that will be publicly available to create mock CIV absorption troughs from quasar winds based on real spectra, and use it to confirm that the line-locking features observed in our outflow composite spectra are physical and not a product of line contamination or systematics. By making use of the composite mocks and real spectra, we then infer parameters characterizing the wind and the radiative power; assuming typical average outflow covering fractions above ~85%, we find a CIV line ratio > 1.5 and N_CIV ~1e14 cm-2, consistent with other literature results, and line locking to be present in over 50% of the absorption troughs in any case. Finally, we estimate that radiative pressure does play a major role in accelerating the winds, via the absorption of about 1% of the total quasar luminosity.