Extreme Gas Kinematics in the z = 2.2 Powerful Radio Galaxy MRC 1138−262: Evidence for Efficient Active Galactic Nucleus Feedback in the Early Universe?

Abstract

To explain the properties of the most massive low-redshift galaxies and the shape of their mass function, recent models of galaxy evolution include strong AGN feedback to complement starburst-driven feedback in massive galaxies. Using the near-infrared integral-field spectrograph SPIFFI on the VLT, we searched for direct evidence for such feedback in the optical emission line gas around the z=2.16 powerful radio galaxy MRC 1138-262, likely a massive galaxy in formation. The kiloparsec-scale kinematics, with FWHMs and relative velocities L* galaxy within a few tens to 100 Myr, fast enough to preserve the observed [α/Fe] overabundance in massive galaxies at low redshift. Using simple arguments, it appears that feedback like that observed in MRC 1138-262 may have sufficient energy to inhibit material from infalling into the dark matter halo and thus regulate galaxy growth as required in some recent models of hierarchical structure formation. Based on observations collected at the European Southern Observatory, Very Large Telescope Array, Cerro Paranal; program Nos. 70.B-0545, 70.A-0229, and 076.A-0684.