Blowin' in the wind: both `negative' and `positive' feedback in an obscured high-z Quasar

TL;DR

This study presents evidence of a quasar at z=1.59 exhibiting both negative and positive feedback effects, with an extended outflow removing gas and triggering star formation at its edges, demonstrating complex galaxy evolution processes.

Contribution

First observational evidence of a galaxy hosting both negative and positive AGN feedback simultaneously in a single system.

Findings

Detected a 1500 km/s extended outflow in [OIII] lines.

Outflow is removing gas from the galaxy center.

Star formation is triggered at the edges of the outflow.

Abstract

Quasar feedback in the form of powerful outflows is invoked as a key mechanism to quench star formation in galaxies, preventing massive galaxies to over-grow and producing the red colors of ellipticals. On the other hand, some models are also requiring `positive' AGN feedback, inducing star formation in the host galaxy through enhanced gas pressure in the interstellar medium. However, finding observational evidence of the effects of both types of feedback is still one of the main challenges of extragalactic astronomy, as few observations of energetic and extended radiatively-driven winds are available. Here we present SINFONI near infrared integral field spectroscopy of XID2028, an obscured, radio-quiet z=1.59 QSO detected in the XMM-COSMOS survey, in which we clearly resolve a fast (1500 km/s) and extended (up to 13 kpc from the black hole) outflow in the [OIII] lines emitting gas, whose large velocity and outflow rate are not sustainable by star formation only. The narrow component of Ha emission and the rest frame U band flux from HST-ACS imaging enable to map the current star formation in the host galaxy: both tracers independently show that the outflow position lies in the center of an empty cavity surrounded by star forming regions on its edge. The outflow is therefore removing the gas from the host galaxy (`negative feedback'), but also triggering star formation by outflow induced pressure at the edges (`positive feedback'). XID2028 represents the first example of a host galaxy showing both types of feedback simultaneously at work.