The NV/CIV ratio in high redshift radio galaxies

Abstract

Deep Keck spectropolarimetry has been obtained of a sample of powerful radio galaxies with $z \sim 2.5 \pm 1$. In addition to a clear 2200à dust scattering/extinction signature and an inverse correlation between the degree of continuum polarization and the Lyman-αemission line strength (relative to C IV), we find an intriguing positive correlation between the N~V/C IV ratio and the polarization. The line ratio, which varies by almost a dex amongst objects having a very similar ionization state, is most likely to indicate an abundance ratio. We speculate that the correlation with polarization represents a connection between nitrogen enhancement and dust production following a major starburst event connected with the birth of the quasar.

6 pages. pdf viewgraphs available at: http://ecf.hq.eso.org/~rfosbury/research/preprints/chemev98/ To appear in "ESO Conference on Chemical Evolution from Zero to High Redshift", Garching, Germany, October 14-16, 1998. ESO Astrophysics Symposia. Eds. J Walsh and M Rosa, Springer