Associated 21-cm absorption towards the cores of radio galaxies

Abstract

We present the results of Giant Metrewave Radio Telescope (GMRT) observations to detect H{\sc i} in absorption towards the cores of a sample of radio galaxies. From observations of a sample of 16 sources, we detect H{\sc i} in absorption towards the core of only one source, the FR\,II radio galaxy 3C\,452 which has been reported earlier by Gupta & Saikia (2006a). In this paper we present the results for the remaining sources which have been observed to a similar optical depth as for a comparison sample of compact steep-spectrum (CSS) and giga-hertz peaked spectrum (GPS) sources. We also compile available information on H{\sc i} absorption towards the cores of extended radio sources observed with angular resolutions of a few arcsec or better. The fraction of extended sources with detection of H{\sc i} absorption towards their cores is significantly smaller (7/47) than the fraction of H{\sc i} detection towards CSS and GPS objects (28/49). For the cores of extended sources, there is no evidence of a significant correlation between H{\sc i} column density towards the cores and the largest linear size of the sources. The distribution of the relative velocity of the principal absorbing component towards the cores of extended sources is not significantly different from that of the CSS and GPS objects. However, a few of the CSS and GPS objects have blue-shifted components $\gapp$1000 km s${}^{-1}$, possibly due to jet-cloud interactions. With the small number of detections towards cores, the difference in detection rate between FR\,I (4/32) and FR\,II (3/15) sources is within the statistical uncertainties.

13 pages, 19 figures, accepted for publication in MNRAS

References in corpus (11)

• The Inner Jet of the Radio Galaxy M87
• Probing radio source environments via HI and OH absorption
• A multifrequency study of giant radio sources-II. Spectral ageing analysis of the lobes of selected sources
• A search for 21 cm HI absorption in AT20G compact radio galaxies
• A multifrequency study of giant radio sources I. Low-frequency Giant Metrewave Radio Telescope observations of selected sources
• Unification scheme and the distribution of neutral gas in compact radio sources
• A Multi-Epoch VLBI Survey of the Kinematics of CJF Sources; Part I: Model-Fit Parameters and Maps
• A search for HI 21cm absorption toward the highest redshift radio loud objects
• VLBI detection of the HST-1 feature in the M87 jet at 2 cm
• HI gas in rejuvenated radio galaxies: GMRT observations of the DDRG J1247+6723
• Associated 21-cm HI absorption towards the radio galaxy 3C452 (J2245+3941)

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