2006MNRAS.370L..80G

We report the detection of 21-cm HI absorption towards the core of the Fanaroff-RileyII radio galaxy 3C452 (J2245+3941). The absorption profile is well resolved into three components; the strongest and narrowest component being coincident with the velocity corresponding to [Oiii] emission lines while the other two components are blueshifted with respect to it by ∼30 and ∼115 km/s. If the systemic velocity of the host galaxy is determined from low-ionization lines, which are redshifted with respect to the [Oiii] doublet by about ∼200 km/s, then both the [Oiii] emission and the 21-cm absorption lines are associated with outflowing material. The neutral hydrogen column density is estimated to be N(HI) = 6.39x10²⁰ (T_s/100) (f_c/1.0)^–1/cm2, where T_s and f_c are the spin temperature and partial coverage of the background source, respectively. If the 21-cm absorber is also responsible for the nuclear extinction at infrared wavelengths and X-ray absorption, then for a spin temperature of ∼8000 K the absorber occults only ∼10 per cent of the radio core.