Deep VLT spectroscopy of the z = 2.49 radio galaxy MRC 2104-242 -: Evidence for a metallicity gradient in its extended emission line region (vol 367, pg L5, 2001)

We present spectroscopic observations of the rest-frame UV line emission around radio galaxy MRC 2104-242 at z = 2.49, obtained with FORS1 on VLT Antu. The morphology of the halo is dominated by two spatially resolved regions. Ly alpha is extended by > 12 along the radio axis, C IV and He II are extended by similar to8 . The overall spectrum is typical for that of high redshift radio galaxies. The most striking spatial variation is that N V is present in the spectrum of the region associated with the center of the galaxy hosting the radio source, the northern region, while absent in the southern region. Assuming that the gas is photoionized by a hidden quasar, the difference in N V emission can be explained by a metallicity gradient within the halo, with the northern region having a metallicity of Z approximate to 1.5 Z(circle dot) and Z less than or equal to 0.4 Z(circle dot) for the southern region. This is consistent with a scenario in which the gas is associated with a massive cooling flow or originates from the debris of the merging of two or more galaxies.