H i gas in rejuvenated radio galaxies: Giant Metrewave Radio Telescope observations of the DDRG J1247+6723

We report the detection of H I absorption towards the inner double of the double-double radio galaxy (DDRG) J1247+6723 with the Giant Metrewave Radio Telescope (GMRT). The inner double is a gigahertz peaked spectrum (GPS) source with a linear size of 14 pc while the overall size defined by the outer double is 1195 kpc, making it a giant radio source. The absorption profile is well resolved and consists of a number of components on either side of the optical systemic velocity. The neutral hydrogen column density is estimated to be N(H I) = 6.73 × 10 20 (T s/100)(1.0/ f c )c m −2 , where T s and f c are the spin temperature and partial coverage of the background source, respectively. We explore any correlation between the occurrence of H I absorption and rejuvenation of radio activity and suggest that there could be a strong relationship between them.