Resolved Infrared Spectroscopy of Two High‐Redshift Radio Galaxies

We report on the rest-frame optical-line emission from the extended gas in two high-redshift radio galaxies, 4C 48.48 at z = 2.343 and 4C 40.36 at z = 2.265. These are among the first observations to obtain rest-frame optical spectra for distinct knots of gas within a high-redshift radio galaxy. Although the dominant ionization mechanism in both sources is photoionization by the central AGNs, we find evidence of another mechanism within the off-nuclear emission of each source. We measure [O II], [Ne III] and [O III] for several regions in 4C 48.48; these measurements indicate shock ionization in one region. We measure seven lines in 4C 40.36 and compare the on- and off-nuclear emission from the two strongest, Hα and [O III]; we find that [O III]/Hα is at least a factor of 4 weaker off-nucleus, suggesting star formation in the extended region.