Detection of non-thermal X-ray emission in the lobes and jets of Cygnus A

Abstract

We present a spectral analysis of the lobes and X-ray jets of Cygnus A, using more than 2 Ms of Chandra observations. The X-ray jets are misaligned with the radio jets and significantly wider. We detect non-thermal emission components in both lobes and jets. For the eastern lobe and jet, we find 1 keV flux densities of 71 +10 −10 nJy and 24 +4 −4 nJy, and photon indices of 1.72 +0.03 −0.03 and 1.64 +0.04 −0.04 respectively. For the western lobe and jet, we find flux densities of 50 +12 −13 nJy and 13 +5 −5 nJy, and photon indices of 1.97 +0.23 −0.10 and 1.86 +0.18 −0.12 respectively. Using these results, we modeled the electron energy distributions of the lobes as broken power laws with age breaks. We find that a significant population of non-radiating particles is required to account for the total pressure of the eastern lobe. In the western lobe, no such population is required and the low energy cutoff to the electron distribution there needs to be raised to obtain pressures consistent with observations. This discrepancy is a consequence of the differing X-ray photon indices, which may indicate that the turnover in the inverse-Compton spectrum of the western lobe is at lower energies than in the eastern lobe. We modeled the emission from both jets as inverse-Compton emission. There is a narrow region of parameter space for which the X-ray jet can be a relic of an earlier active phase, although lack of knowledge about the jet's electron distribution and particle content makes the modelling uncertain.

Unveiling the cause of hybrid morphology radio sources (HyMoRS)

“…As the hotspots and core are necessarily misaligned, identification of these sources is difficult without sufficient diffuse emission to confidently associate the three components, meaning the total number of bent-jet FR II therefore currently remains unknown. The short baselines, low frequency, and resolution provided by LOFAR (van Haarlem et al 2013) mean that the forthcoming LOFAR Two Meter Sky Survey (LoTSS) data release 2 will help to resolve these issues by providing a large sample of sources in which complex morphology objects can be confidently identified and will therefore be the subject of future work to test the prevalence of both bent-jet FR IIs and hybrid morphology sources (Harwood and Mingo, in prep).…”

High-resolution international LOFAR observations of 4C 43.15

“…The closest example of such an object is the well-studied radio galaxy Cygnus A (e.g. Carilli et al 1991;Steenbrugge et al 2010;McKean et al 2016;de Vries et al 2018; hereafter Cyg A). We therefore first compare our findings for 4C 43.15 with it and two other nearby sources studied in Harwood et al (2016) and Harwood et al (2017): 3C 223 and 3C 452, z = 0.137 and z = 0.081, respectively.…”

AGN feedback in the FR II galaxy 3C 220.1

“…X-ray emission in the lobes can have contributions from inverse Compton (IC) emission, produced by photons being IC-scattered to X-ray energies by the radio-synchrotron emitting electrons. IC emission has been observed in many FR II radio lobes (e.g., Isobe et al 2002;Bondi et al 2004;Hardcastle & Croston 2010;Croston et al 2005;Ineson et al 2017;de Vries et al 2018). In order to check for IC Xray emission in the lobes, we chose two elliptical regions for the lobes based on Fig.…”