Giant outflows in z~2 radio galaxies: The smoking gun of AGN feedback in the early universe

TL;DR

This study provides observational evidence of powerful ionized outflows driven by AGN activity in z~2 radio galaxies, supporting models of AGN feedback influencing galaxy evolution and the intergalactic medium in the early universe.

Contribution

It reports the detection of large-scale ionized and molecular gas outflows in high-redshift radio galaxies, highlighting the interaction between AGN jets and the surrounding medium, a novel insight into early universe galaxy dynamics.

Findings

Kpc-sized ionized gas outflows with velocities ~1000 km/s.

Significant deficit of cold molecular gas relative to ionized gas.

Detection of cold molecular gas reservoir near radio hot spots.

Abstract

AGN feedback is now a major component of models of galaxy evolution. Using near-infrared imaging spectroscopy on the VLT we identify kpc-sized outflows of few x 10^10 M_s of ionized gas in powerful radio galaxies at z~2-3. Velocity fields are consistent with bipolar outflows, with total velocity offsets of ~1000 km s-1. FWHMs ~1000 km s-1 suggest strong turbulence. IRAM follow-up observations of parts of the sample suggest a remarkable deficit in cold molecular relative to ionized gas, which may imply that significant fractions of the interstellar medium of these galaxies are participating in the winds. Kinetic energies of the gas correspond to ~0.2% of the rest-mass equivalent of the mass of the supermassive black hole, roughly in agreement with model predictions. We also report the detection of a massive reservoir of few x 10^10 M_s of cold molecular gas in the halo of the z=2.6 radio galaxy TXS0828+193 with the IRAM Plateau de Bure Interferometer. The gas is at a distance of ~90 kpc from the radio galaxy, and does not appear associated with a significant stellar mass > few x10^9 M_s. It is near one of the radio hot spots, and at a very similar redshift to the diffuse, Mpc-sized halo of ionized gas surrounding the radio galaxy. This may be the first sign that the jets of powerful radio galaxies at z~2 may interact efficiently with the intracluster medium, somewhat in analogy with the filaments of multiphase gas in nearby galaxy clusters which are being heated by the powerful AGN of their central galaxies.