Near-Infrared Spectroscopy of Powerful Radio Galaxies at z=2.2-2.4

Abstract

Near-infrared spectroscopy (rest-frame 3700-6800 Angstroms) of eight high redshift powerful radio galaxies (HzPRGs) at z = 2.2-2.6 is presented. Strong forbidden lines and H-alpha emission were detected in all sources; the data show evidence that the emission lines of the HzPRGs may contribute a substantial fraction (approx. 25-98%) of their total observed H - and/or K -band light. Diagnostic emission-line ratios for three of the eight HzPRGs are consistent with the presence of a Seyfert 2 nucleus; the [O III] 5007 / H-beta and [S II] 6716, 6731 / H-alpha ratios and/or limits of the remaining five galaxies are inconclusive. Furthermore, all six of the galaxies for which both H - and K -band spectra were obtained have observed [O III] 5007 / (H-alpha +[N II] 6548, 6583) ratios consistent with Seyfert 2 ionization...