We present new XMM-Newton data of the high-redshift (z=1.883), Mpc-sized giant radio galaxy 6C 0905+39. The larger collecting area and longer observation time for our new data means that we can better characterise the extended X-ray emission, in part
icular its spectrum, which arises from cosmic microwave background photons scattered into the X-ray band by the energetic electrons in the spent synchrotron plasma of the (largely) radio-quiet lobes of 6C 0905+39. We calculate the energy that its jet-ejected plasma has dumped into its surroundings in the last 3 X 10^7 years and discuss the impact that similar, or even more extreme, examples of spent, radio-quiet lobes would have on their surroundings. Interestingly, there is an indication that the emission from the hotspots is softer than the rest of the extended emission and the core, implying it is due to synchrotron emission. We confirm our previous detection of the low-energy turnover in the eastern hotspot of 6C 0905+39.
Our XMM-Newton spectrum of the giant, high-redshift (z=1.88) radio galaxy 6C 0905+39 shows that it contains one of the most powerful, high-redshift, Compton-thick quasars known. Its spectrum is very hard above 2 keV. The steep XMM spectrum below that
energy is shown to be due to extended emission from the radio bridge using Chandra data. The nucleus of 6C 0905+39 has a column density of 3.5 (+1.4,-0.4) X 10^24 cm^-2 and absorption-corrected X-ray luminosity of 1.7 (+0.9,-0.1) X 10^45 erg/s in the 2-10 keV band. A lower redshift active galaxy in the same field, SDSS J090808.36+394313.6, may also be Compton-thick.
We report the discovery of an X-ray counterpart to the southern radio hotspot of the largest-known radio quasar 4C 74.26 (whose redshift is z=0.104). Both XMM-Newton and Chandra images reveal the same significant (10arcsec, i.e. 19kpc) offset between
the X-ray hotspot and the radio hotspot imaged with MERLIN. The peak of the X-ray emission may be due to synchrotron or inverse-Compton emission. If synchrotron emission, the hotspot represents the site of particle acceleration and the offset arises from either the jet exhibiting Scheuers `dentists drill effect or a fast spine having less momentum than the sheath surrounding it, which creates the radio hotspot. If the emission arises from the inverse-Compton process, it must be inverse-Compton scattering of the CMB in a decelerating relativistic flow, implying that the jet is relativistic (Gamma >= 2) out to a distance of at least 800kpc. Our analysis, including optical data from the Liverpool Telescope, rules out a background AGN for the X-ray emission and confirms its nature as a hotspot, making it the most X-ray luminous hotspot yet detected.
