The reddened quasar 3C 22 and its implications

We prove the presence of a broad ($$\approx 5000 \enspace\text{km} \enspace {\text s^{-1}}$$) Hα emission line in the spectrum of the $$z=0.935$$ ‘radio galaxy’ 3C 22. This confirms suspicions that some of the faint red objects classified as high-redshift radio galaxies are actually slightly reddened quasars. Using our WHT and UKIRT spectra, we estimate a rest-frame extinction towards the quasar of $$A_V\sim2$$. We review the difficulties involved in detecting broad emission lines in high-redshift radio galaxies, concluding that, if one wishes to discover the origin of the observed near-infrared light, then near-infrared spectroscopy is a very limited technique. We argue that a programme of thermal imaging is likely to prove far more fruitful.