Publication Date:
2017-01-02
Description:
We have used the 610-MHz receivers of the Giant Metrewave Radio Telescope (GMRT) to detect associated H i 21-cm absorption from the z = 1.2230 blazar TXS 1954+513. The GMRT H i 21-cm absorption is likely to arise against either the milliarcsecond-scale core or the one-sided milliarcsecond-scale radio jet, and is blueshifted by 328 km s –1 from the blazar redshift. This is consistent with a scenario in which the H i cloud giving rise to the absorption is being driven outwards by the radio jet. The integrated H i 21-cm optical depth is (0.716 ± 0.037) km s –1 , implying a high H i column density, $N_{\rm H\small {I}} = (1.305 \pm 0.067) \times ({ T_{\rm s}/100\,{\rm K}}) \times 10^{20}$ cm –2 , for an assumed H i spin temperature of 100 K. We use Nickel Telescope photometry of TXS 1954+513 to infer a high rest-frame 1216 Å luminosity of (4.1 ± 1.2) x 10 23 W Hz –1 . The z = 1.2230 absorber towards TXS 1954+513 is only the fifth case of a detection of associated H i 21-cm absorption at z 〉 1, and is also the first case of such a detection towards an active galactic nucleus (AGN) with a rest-frame ultraviolet (UV) luminosity 〉〉10 23 W Hz –1 , demonstrating that neutral hydrogen can survive in AGN environments in the presence of high UV luminosities.
Print ISSN:
0035-8711
Electronic ISSN:
1365-2966
Topics:
Physics
