Probing the absorbing haloes around two high - redshift radio galaxies with VLT - UVES ⋆

We present VLT-UVES echelle spectroscopy of the HI and C IV absorption in the spatiallyextended Lyα emission around two high-redshift radio galaxies 0200+015 (z=2.23) and 0943242 (z=2.92). The absorbers in 0943-242 exhibit little additional structure compared with previous lowresolution spectroscopy and the main absorber is still consistent with HI column density of ∼ 10 cm . This is consistent with a picture in which the absorbing gas has low density and low metallicity and is distributed in a smooth absorbing shell located beyond the emissionline gas. However, the main absorbers in 0200+015 are very different. The previous single absorber fit of HI column density ≃ 10 cm , now splits into two ∼ 4 × 10 cm absorbers which extend more than 15 kpc to obscure additional Lyα emission coincident with a radio lobe in these high-resolution observations. Although consistent with the shell-like distribution for the absorption systems, 0200+015 requires a much higher metal enrichment than 0943-242. The metallicity, inferred from the C IV absorption, is considerably lower in 0943242 than in 0200+015. We explain these differences with an evolutionary scenario based on the size of the radio source. In both sources the HI absorption gas originates from either a gas-rich merger or pristine cluster gas which cools and collapses towards the centre of the dark matter halo. The higher metallicity in the larger radio source (0200+015) may be a result of a starburst driven superwind (concurrent with the triggering of the radio emission) which has engulfed the outer halo in this older source. We also find a significant blue asymmetry in the HeIIλ1640 emission line, suggesting that the line emitting gas is outflowing from the central regions. Dust obscuration toward the central engine, presumably due to the dusty torus invoked in Unified Scheme, prevents us from seeing outflow away from our line-of-sight.