The role of neutral hydrogen in radio galaxies

We present morphological and statistical results of a study of neutral hydrogen (HI) in a complete sample of nearby, non-cluster radio galaxies. We detect large-scale HI emission in the early-type host galaxies of 25% of our sample sources. The large-scale HI is mainly distributed in disk- and ring-like structures with sizes upto 190 kpc and masses upto 2 × 1010 M⊙. All radio galaxies with MHI ≳ 109 M⊙ have a compact radio source. When we compare our sample of radio-loud early-type galaxies with samples of radio-quiet early-type galaxies there appears to be no significant difference in HI properties (mass, morphology and detection rate). This suggests that that the radio-loud phase could be just a short phase that occurs at some point during the life-time of many, or even all, early-type galaxies.