3. The data
We have constructed a sample which comprises 21 narrow line radio galaxies at high z (most of them have 2) for which the UV CIV 1550, HeII 1640 and CIII] 1909 emission lines have been measured. We have excluded those objects which show evidence of a BLR. In Table 1, we list the object names, the line ratios of interest to us here, the redshift and the reference to the observations. Most of the data are taken from the recent thesis by van Ojik (1995) which includes objects selected on the basis of a very steep radio spectrum. The other objects have been selected from the literature with the criteria of having high redshifts, classified as narrow line radio galaxies and with measured fluxes for the three UV lines mentioned above.
Table 1. Observed UV line ratios for several high z radio galaxies with no apparent broad component
The line measurements refer to the integrated emission from the object collected with a long slit aligned with the radio axis. We know that at this redshift, the line luminosities are generally dominated by the extranuclear emission and we can be confident that the general properties of the emitting gas inferred from the spectra describe the extended emitting regions, rather than the emission line regions close to the nuclei.
© European Southern Observatory (ESO) 1997
Online publication: June 5, 1998