Outflows of stars due to quasar feedback

TL;DR

This paper demonstrates through simulations that quasar feedback can eject not only gas but also stars from galaxies, impacting galaxy evolution and the distribution of stars.

Contribution

It introduces a novel mechanism where AGN-driven outflows can accelerate and eject stars, a process not previously emphasized in galaxy feedback models.

Findings

AGN feedback can eject stars under certain conditions.

Black holes exceeding M_sigma mass can drive star ejection.

Ejected stars can influence galaxy evolution and enrichment.

Abstract

Quasar feedback outflows are commonly invoked to drive gas out of galaxies in the early gas-rich epoch to terminate growth of galaxies. Here we present simulations that show that AGN feedback may drive not only gas but also stars out of their host galaxies under certain conditions. The mechanics of this process is as following: (1) AGN-driven outflows accelerate and compress gas filling the host galaxy; (2) the accelerated dense shells become gravitationally unstable and form stars on radial trajectories. For the spherically symmetric initial conditions explored here, the black hole needs to exceed the host's M_sigma mass by a factor of a few to accelerate the shells and the new stars to escape velocities. We discuss potential implications of these effects for the host galaxies: (i) radial mixing of bulge stars with the rest of the host; (ii) contribution of quasar outflows to galactic fountains as sources of high-velocity clouds; (iii) wholesale ejection of hyper velocity stars out of their hosts, giving rise to type II supernovae on galactic outskirts, and contributing to reionization and metal enrichment of the Universe; (iv) bulge erosion and even complete destruction in extreme cases resulting in overweight or bulgeless SMBHs.