Can AGN feedback-driven star formation explain the size evolution of massive galaxies?

TL;DR

This paper proposes that AGN feedback-driven star formation, triggered by radiation pressure on dusty gas, can explain the significant size growth of massive galaxies over the past 10 billion years, offering an alternative to merger models.

Contribution

It introduces a novel model where AGN feedback induces star formation in outflows, contributing to galaxy size evolution, which has not been extensively explored before.

Findings

Stars form in feedback-driven outflows at larger radii.

The model predicts size and mass growth consistent with observations.

Obscuration by dust affects star formation signatures.

Abstract

Observations indicate that massive galaxies at z~2 are more compact than galaxies of comparable mass at z~0, with effective radii evolving by a factor of ~3-5. This implies that galaxies grow significantly in size but relatively little in mass over the past ~10 Gyr. Two main physical models have been proposed in order to explain the observed evolution of massive galaxies: "mergers" and "puffing-up" scenarios. Here we introduce another possibility, and discuss the potential role of the central active galactic nucleus (AGN) feedback on the evolution of its host galaxy. We consider triggering of star formation, due to AGN feedback, with radiation pressure on dusty gas as the driving feedback mechanism. In this picture, stars are formed in the feedback-driven outflow at increasingly larger radii and build up the outer regions of the host galaxy. The resulting increase in size and stellar mass can be compared with the observed growth of massive galaxies. Star formation in the host galaxy is likely obscured due to dust extinction and reddening. We suggest a number of observational predictions of our model, and discuss possible implications for AGN feedback-driven star formation.