Radiation pressure powers quasar broad absorption line winds but fails to drive galaxy feedback

Most cosmological simulations invoke quasar-driven winds as the primary mechanism quenching star formation in massive galaxies, assuming that wind momentum flux approaches the radiation-pressure maximum, L/c.

Using 81,388 broad absorption line troughs from the SDSS-IV DR16 quasar catalog and detailed mock trough spectra, the authors detect line locking—a spectral signature of radiation-pressure-driven outflows—in 60 to 70 percent of troughs. This demonstrates that radiative line driving dominates wind acceleration and rules out alternative mechanisms.

Direct measurement of the wind energy budget yields a median kinetic luminosity of only 0.01 percent of bolometric luminosity, 50 times below the level required for effective feedback. Consequently, line-driven quasar winds are insufficiently powerful to quench star formation, challenging the primary physical mechanism invoked for black hole feedback in galaxy formation models.