X-ray emission around the z = 4.1 radio galaxy TN J1338−1942 and the potential role of far-infrared photons in AGN feedback

• Published in: Monthly notices of the Royal Astronomical Society 2013-10, Vol.434 (4), p.3246-3251
• Main Authors: Smail, Ian, Blundell, Katherine M.
• Format: Article
• Language: English
• Subjects: Atoms & subatomic particles; Cosmic microwave background temperature; Electrons; Star & galaxy formation; Starbursts; X-ray astronomy
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1093/mnras/stt1240

We report the discovery in an 80-ks observation of spatially extended X-ray emission around the high-redshift radio galaxy TN J1388−1942 (z = 4.11) with the Chandra X-ray Observatory. The X-ray emission extends over a ∼30-kpc diameter region and although it is less extended than the GHz-radio lobes, it is roughly aligned with them. We suggest that the X-ray emission arises from inverse-Compton (IC) scattering of photons by relativistic electrons around the radio galaxy. At z = 4.11, this is the highest redshift detection of IC emission around a radio galaxy. We investigate the hypothesis that in this compact source, the cosmic microwave background (CMB), which is ∼700× more intense than at z ∼ 0 is nonetheless not the relevant seed photon field for the bulk of the IC emission. Instead, we find a tentative correlation between the IC emission and far-infrared luminosities of compact, far-infrared luminous high-redshift radio galaxies (those with lobe lengths of 100 kpc). Based on these results, we suggest that in the earliest phases of the evolution of radio-loud active galactic nuclei at very high redshift, the far-infrared photons from the co-eval dusty starbursts occurring within these systems may make a significant contribution to their IC X-ray emission and so contribute to the feedback in these massive high-redshift galaxies.