SIMBAD references

Using MUSE on the ESO-VLT, we obtained a four-hour exposure of the z=3.12 radio galaxy MRC 0316-257. We detect features down to ∼10^–19erg/s/cm²/arcsec², with the highest surface brightness regions reaching more than a factor of 100 higher. We find Lyα emission out to ∼250kpc in projection from the active galactic nucleus (AGN). The emission shows arc-like morphologies arising at 150-250kpc from the nucleus in projection, with the connected filamentary structures reaching down into the circumnuclear region. The most distant arc is offset by ∼700km/s relative to circumnuclear HeIIλ1640 emission, which we assume to be at the systemic velocity. As we probe emission closer to the nucleus, the filamentary emission narrows in projection on the sky, the relative velocity decreases to ∼250km/s, and the line full-width at half maximum ranges from ∼300-700km/s. From UV line ratios, the emission on scales of 10s ofkpc from the nucleus along a wide angle in the direction of the radio jets is clearly excited by the radio jets and ionizing radiation of the AGN. Assuming ionization equilibrium, the more extended emission outside of the axis of the jet direction would require 100% or more illumination to explain the observed surface brightness. High-speed (≥300km/s) shocks into rare gas would provide sufficiently high surface brightness. We discuss the possibility that the arcs of Lyα emission represent accretion shocks and the filamentary emission represents gas flows into the halo, and compare our results with gas accretion simulations.