Quasar feedback in the early Universe: the case of SDSS J1148+5251

TL;DR

This paper models quasar feedback in the early universe, specifically in SDSS J1148+5251, showing that active galactic nuclei-driven outflows can explain observed gas depletion and star formation suppression at high redshift.

Contribution

It presents a semi-analytical model that predicts quasar-driven outflows matching observations, highlighting the role of quasar feedback in early galaxy evolution.

Findings

Predicted outflow rate aligns with observed lower limit of 3500 Msun/yr.

Quasar feedback dominates gas outflows at z=6.4, reducing star formation.

Supernovae contribute negligibly to the observed winds at this epoch.

Abstract

Galaxy-scale gas outflows triggered by active galactic nuclei have been proposed as a key physical process to regulate the co-evolution of nuclear black holes and their host galaxies. The recent detection of a massive gas outflow in one of the most distant quasar, SDSS J1148+5251 at z = 6.4, presented by Maiolino et al. (2012) strongly supports this idea and suggests that strong quasar feedback is already at work at very early times. In a previous work, Valiante et al. (2011), we have presented a hierarchical semi-analytical model, GAMETE/ QSOdust, for the formation and evolution of high-redshift quasars, and we have applied it to the quasar SDSS J1148+5251, with the aim of investigating the star formation history, the nature of the dominant stellar populations and the origin and properties of the large dust mass observed in the host galaxy. A robust prediction of the model is that the evolution of the nuclear black hole and of the host galaxy are tightly coupled by quasar feedback in the form of strong galaxy-scale winds. In the present letter, we show that the gas outflow rate predicted by GAMETE/QSOdust is in good agreement with the lower limit of 3500 Msun/yr inferred by the observations. According to the model, the observed outflow at z = 6.4 is dominated by quasar feedback, as the outflow rate has already considerably depleted the gas content of the host galaxy, leading to a down-turn in the star formation rate at z < 7 - 8. Hence, supernova explosions give a negligible contribution to the observed winds at z = 6.4.