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

Observations indicate that massive galaxies at z similar to 2 are more compact than galaxies of comparable mass at z similar to 0, with effective radii evolving by a factor of similar to 3-5. This implies that galaxies grow significantly in size but relatively little in mass over the past similar to 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.