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HI in the proto-cluster environment at z>2: absorbing haloes and the Lyman alpha forest

R. J. Wilman·M. J. Jarvis·H. J. A. Rottgering·L. Binette
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Abstract

We present VLT-UVES echelle spectra of the Lyman alpha emission and absorption in five radio galaxies at redshifts z=2.55-4.1. Together with data from our pilot study, we have a sample of 7 such systems with radio source sizes ~ 1-90 kpc with which to address the origin of the absorbing gas. Echelle resolution again reveals that some systems with N_HI>1E18 cm^-2 in lower resolution data in fact consist of several weaker absorbers with N_HI<1E15 cm^-2. We identify two groups of HI absorbers: strong absorbers with N_HI=1E18-1E20 cm^-2 and weaker systems with N_HI=1E13-1E15 cm^-2. There are none at intermediate N_HI. The strong absorbers may be a by-product of massive galaxy formation or could instead represent material cooling behind the expanding bow-shock of the radio jet, as simulated by Krause. New observations are required to discriminate between these possibilities. We argue that the weaker absorbers with N_HI=1E13-1E15 cm^-2 are part of the Lyman alpha forest, as their rate of incidence is within a factor of 2-4 of that in the IGM at large. Such column densities are consistent with models of a multi-phase proto-intracluster medium at z>2.

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R. J. Wilman, M. J. Jarvis, H. J. A. Rottgering, L. Binette. 2004-03-22. HI in the proto-cluster environment at z>2: absorbing haloes and the Lyman alpha forest. https://doi.org/10.1111/j.1365-2966.2004.07857.x

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