The Transition from Galaxy-wide Gas Inflow to Outflow in Quasar Host Galaxies

TL;DR

This study reveals a transition from gas inflow to outflow in quasar host galaxies, linking early AGN activity with galaxy-wide outflows that influence galaxy evolution.

Contribution

It uncovers the novel phenomenon of inflow-to-outflow transition in quasars and connects it to AGN evolution and feedback mechanisms.

Findings

Galaxy-scale inflow transitions to outflow as AGN evolves.

Outflows are stronger at early AGN stages with high accretion.

Observed outflow transformation supports multi-stage AGN feedback models.

Abstract

Galactic-wide outflows driven by active galactic nuclei (AGNs) is a routinely invoked feedback mechanism in galaxy evolution models. Hitherto, the interplay among the interstellar gas on galactic scales, the propagation of AGN outflows and the fundamental AGN parameters during evolution remains elusive. Powerful nuclear outflows are found to favorably exist at early AGN stages usually associated with high accretion rates and weak narrow emission lines. In a sample of quasars emitting Mg II narrow absorption lines (NALs) from the Sloan Digital Sky Survey, we discover an unprecedented phenomenon where galaxy-scale inflow-dominated transforming into outflow-dominated gas accompanied by an increasing strength of the narrow [O III] line, at a confidence level of 6.7{\sigma}. The fact that nuclear outflows diminish while galaxy-wide outflows intensifies as AGNs evolve implies that early-stage outflows interact with interstellar medium on galactic scales and trigger the gradual transformation into galaxy-wide outflows, providing observational links to the hypothetical multi-stage propagation of AGN outflows that globally regulates galaxy evolution.