A&A 414, 927-929 (2004)
revisited: The environments of low-excitation radio galaxies and unified modelsM. J. Hardcastle
Department of Physics, University of Bristol, Tyndall Avenue, Bristol BS8 1TL, UK
(Received 31 October 2003 / Accepted 24 November 2003 )
Recent measurements of the galaxy clustering environments around intermediate-redshift radio sources have suggested a systematic environmental difference between radio galaxies and radio-loud quasars, in contradiction to the predictions of simple unified models for the two classes of object. I show that the apparent difference arises mainly as a result of the properties of low-excitation radio galaxies included in the radio-galaxy sample, which tend to lie in significantly richer environments. The environmental properties of high-excitation radio galaxies and quasars are statistically consistent in the redshift range 0.15 < z <0.4 , as unified models would predict.
Key words: galaxies: active -- galaxies: quasars: general -- galaxies: clusters: general -- radio continuum: galaxies
© ESO 2004