Open AccessAssociated 21‐cm H i absorption towards the radio galaxy 3C 452 (J2245+3941)
Author(s) -
Gupta Neeraj,
Saikia D. J.
Publication year - 2006
Publication title -
monthly notices of the royal astronomical society: letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.067
H-Index - 122
eISSN - 1745-3933
pISSN - 1745-3925
DOI - 10.1111/j.1745-3933.2006.00193.x
Subject(s) - physics , astrophysics , redshift , galaxy , absorption (acoustics) , absorption spectroscopy , radio galaxy , extinction (optical mineralogy) , ionization , emission spectrum , spectral line , astronomy , optics , ion , quantum mechanics
ABSTRACT We report the detection of 21‐cm H i absorption towards the core of the Fanaroff–Riley II radio galaxy 3C 452 (J2245+3941). The absorption profile is well resolved into three components; the strongest and narrowest component being coincident with the velocity corresponding to [O iii ] emission lines while the other two components are blueshifted with respect to it by ∼30 and ∼115 km s −1 . If the systemic velocity of the host galaxy is determined from low‐ionization lines, which are redshifted with respect to the [O iii ] doublet by about ∼200 km s −1 , then both the [O iii ] emission and the 21‐cm absorption lines are associated with outflowing material. The neutral hydrogen column density is estimated to be N (H i ) = 6.39 × 10 20 ( T s /100) ( f c /1.0) −1 cm −2 , 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.