Lyman-alpha absorption : links between CSS quasars and high-redshift radio galaxies

Spectroscopy of high-redshift compact steep-spectrum (CSS) quasars shows a high incidence of Ly-alpha absorption close to the quasar redshift. Associated absorption systems like these are rare in other types of radio sources, with the notable exception of high-redshift radio galaxies (HZRGs). CSS quasars and HZRGs share many properties; the hypothesis that they are intrinsically similar objects is presented and discussed.