Direct Evidence for AGN Feedback from Fast Molecular Outflows in Reionization-Era Quasars

TL;DR

This study provides the first direct evidence of fast, cold molecular outflows driven by AGN in reionization-era quasars at z>6, highlighting their potential role in galaxy evolution.

Contribution

It presents the first survey detecting cold molecular outflows in z>6 quasars, showing their high velocities and partial AGN influence, advancing understanding of early galaxy feedback mechanisms.

Findings

Unambiguous outflows detected in 73% of quasars

Outflow velocities are ~300 km/s higher than in non-quasar galaxies

Kinetic power of outflows is about 0.1% of AGN luminosity

Abstract

Galactic outflows driven by rapidly-accreting quasars at high redshift are widely expected to play a key role in the short- and long-term future evolution of their host galaxies. Using new and archival ALMA data, we observed the OH 119um doublet lines in order to search for cold molecular outflows in a sample of 11 unobscured, IR-luminous quasars at z>6. This represents the first survey for molecular winds in reionization-era quasars, and we detect unambiguous outflows in 8/11 (73%) of the quasars. The outflows we find are substantially faster, by ~300km/s on average, than outflows observed in a roughly co-eval sample of non-quasar IR-luminous galaxies, suggesting that the AGN drive the winds to higher velocities. On the other hand, the implied molecular outflow rates are relatively modest given the high luminosities, suggesting typical mass loading factors ~0.5 in the cold gas. The outflows are consistent with expectations for momentum-driven winds regardless of the driving source, but the kinetic energy in the outflows suggests that the AGN must be at least partially responsible for driving the winds. Accordingly, we find trends between the outflow properties and the Eddington ratio of the black hole accretion, though this may be linked to the underlying trend with AGN luminosity. We find that the kinetic power carried in the cold outflow phase is typically only ~0.1% of the total AGN luminosity. Our study provides evidence in favor of AGN feedback on the cold molecular gas in $z>6$ quasar host galaxies, demonstrating that cold outflows are very common and powerful in the most extreme reionization-era quasars.