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

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 discussthe 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 massivegalaxies. Star formation in the host galaxy is likely obscured due to dust extinction and reddening.We suggest a number ofobservational predictions of our model, and discuss possible implications for AGN feedback-driven star formation. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.