TXS 1433+205: The most distant gamma-ray emitting FR II radio galaxy

The orientation of the jet axis to the line of sight of the observer plays a major role in explaining the phenomena observed from blazars and radio galaxies. In the gamma-ray band, only a handful of radio galaxies have been identified, all being located in the nearby Universe (z<0.5). Here we report the identification of 4FGL J1435.5+2021, associated with TXS 1433+205, as a Fanaroff-Riley type II (FR II) radio galaxy at a considerably higher redshift of z=0.748, thereby making it the most distant gamma-ray detected radio galaxy known as of now. The Very Large Array Sky Survey data at 3 GHz resolves the source morphology into a bright core, a jet and two hotspots, with a total end-to-end projected length between lobe extremities of ~170 kpc. The optical and radio properties of this enigmatic object suggest it to be a high-excitation FR II radio galaxy. The multi-wavelength behaviour of TXS 1433+205 is found to be similar to other gamma-ray detected FR II sources but is at the high luminosity end. We suggest that the ongoing and upcoming high-resolution radio surveys will lead to the identification of many more high-redshift radio galaxies in the gamma-ray sky, thus allowing comprehensive studies of misaligned relativistic jets.
Comment: MNRAS Letters, in press