Search

Narrowband Ly α imaging has been carried out around eight radio galaxies at 2 to search for (proto-)cluster galaxies at the same redshift. Subsequent spectroscopy has led to the discovery of six protoclusters at redshifts z=2.2, 2.9, 2.9, 3.1, 3.2 and 4.1, with velocity dispersions between 300 km s−1 and 1000 km s−1. The estimated masses are in the range 1014–1016 M⊙, comparable to the mass of present day rich clusters of galaxies. [Copyright &y& Elsevier]

Keck LRISp optical spectropolarimetry and VLT ISAAC NIR spectroscopy of an overlapping sample of z∼2.5 radio galaxies has provided a set of uniquely high quality spectra stretching from Ly α to Hα. The measurement of emission and absorption line strengths, continuum polarization and SED allow us to quantify the various emission and scattering mechanisms that comprise the observed spectra. We identify this epoch as critical in the chemical evolution of massive spheroids and show that, while star formation must be very active, most of the UV/optical radiation we see from these luminous sources derives from the AGN. [Copyright &y& Elsevier]

We summarise the properties of the absorbing haloes around two high-redshift radio galaxies studied with the VLT-UVES echelle spectrograph. The absorbers in 0943−242 (z=2.92) exhibit little further structure compared with previous data—the main absorber still has N(HI)≃1019 cm−2—reinforcing the picture in which the absorbing gas occupies a smooth shell beyond the emission line halo. In 0200+015 (z=2.23) the main absorber now splits into two spatially-resolved systems with N(HI)≃4×1014 cm−2, one of which has strong CIV absorption, implying a metallicity of Z≃10 Z◎. We explain the differences between the two sources with an evolutionary scenario, invoking interaction with the expanding radio source and metal enrichment via a starburst superwind. [Copyright &y& Elsevier]

Powerful radio galaxies often display enhanced optical/UV continuum emission and extended emission line regions, elongated and aligned with the radio jet axis. The expansion of the radio source strongly affects the gas clouds in the surrounding IGM, and the kinematic and ionization properties of the extended emission line regions display considerable variation over the lifetime of individual sources, as well as with cosmic epoch. We present the results of deep rest-frame UV and optical imaging and UV spectroscopy of high redshift 6C radio galaxies. The interdependence of the host galaxy and radio source properties are discussed, considering: (i) the relative contribution of shocks associated with the expanding radio source to the observed emission line gas kinematics, and their effect on the ionization state of the gas; (ii) the similarities and differences between the morphologies of the host galaxies and aligned emission for a range of radio source powers; and (iii) the influence of radio power on the strength of the observed alignment effect. [Copyright &y& Elsevier]