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Publication - Professor Mark Birkinshaw

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


    Vries, MNd, Wise, MW, Huppenkothen, D, Nulsen, PEJ, Snios, B, Hardcastle, MJ, Birkinshaw, M, Worrall, DM, Duffy, RT & McNamara, BR, 2018, ‘Detection of non-thermal X-ray emission in the lobes and jets of Cygnus A’. Monthly Notices of the Royal Astronomical Society, vol 478., pp. 4010-4029


    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.

    Full details in the University publications repository