IGR J17488-2338: a newly discovered giant radio galaxy

Abstract

We present the discovery of a large scale radio structure associated with IGR J17488--2338, a source recently discovered by \emph{INTEGRAL} and optically identified as a broad line AGN at redshift 0.24. At low frequencies, the source properties are those of an intermediate-power FR II radio galaxy with a linear size of 1.4\,Mpc. This new active galaxy is therefore a member of a class of objects called Giant Radio Galaxies (GRGs), a rare type of radio galaxies with physical sizes larger than 0.7\,Mpc; they represent the largest and most energetic single entities in the Universe and are useful laboratories for many astrophysical studies. Their large scale structures could be due either to special external conditions or to uncommon internal properties of the source central engine The AGN at the centre of IGR J17488--2338 has a black hole of 1.3$\times$10$^9$ solar masses, a bolometric luminosity of 7$\times$10$^{46}$erg\,s$^{-1}$ and an Eddington ratio of 0.3, suggesting that it is powerful enough to produce the large structure observed in radio. The source is remarkable also for other properties, among which its X-ray absorption, at odds with its type 1 classification, and the presence of a strong iron line which is a feature not often observed in radio galaxies.