The impact of AGN outflows on the surface habitability of terrestrial planets in the Milky Way

TL;DR

This paper investigates how active galactic nucleus (AGN) outflows could affect the habitability of Earth-like planets in the Milky Way by causing atmospheric heating, escape, and ozone depletion within approximately 1 kiloparsec.

Contribution

It introduces simple models to estimate the distance within which AGN outflows impact planetary atmospheres and explores their potential influence on galactic habitability.

Findings

AGN winds can cause atmospheric heating and escape.

AGN outflows may deplete ozone layers on nearby planets.

Effects are significant within about 1 kiloparsec from the galactic center.

Abstract

It is well-known that active galactic nuclei (AGN) are accompanied by winds and outflows, some of which may reach weakly relativistic speeds of about $10$ percent the speed of light. Yet, in spite of their ubiquity, the impact of AGN outflows in modulating surface habitability of terrestrial planets on galactic scales, using the Milky Way as the basis for comparison, is poorly investigated and inadequately understood. In this work, we address this issue by focusing on two key mechanisms: AGN winds can heat atmospheres and drive atmospheric escape, as well as stimulate the formation of nitrogen oxides and thence cause ozone depletion. By developing simple models, we estimate the maximal distance up to which these deleterious effects are rendered significant for Earth-like planets in the Milky Way, and thereby demonstrate that this value may extend to $\lesssim 1$ kpc. In the case of quasars hosting larger supermassive black holes, such effects could actually influence the AGN host galaxy as a whole.