The spectral structure and energetics of powerful radio sources

J. J. Harwood1*, M. J. Hardcastle1, J. H. Croston2, A. Stroe3, R. Morganti4,5 and E. Orrù4
1School of Physics, Astronomy and Mathematics, University of Hertfordshire, College Lane, Hatfield, Hertfordshire AL10 9AB, UK
2School of Physics and Astronomy, University of Southampton, Southampton SO17 1BJ, UK
3Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
4Netherlands Institute for Radio Astronomy (ASTRON), Postbus 2, 7990 AA Dwingeloo, The Netherlands
5Kapteyn Astronomical Institute, University of Groningen, Post Office Box 800, 9700 AV Groningen, The Netherlands

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Determining the energy spectrum of an electron population can give key insights into the underlying physics of a radio source; however, the lack of high resolution, broad-bandwidth observations has left many ambiguities in our understanding of radio galaxies. The improved capabilities of telescopes such as the JVLA and LOFAR mean that within the bandwidth of any given observation, a detailed spectral shape can now be produced. We present recent investigations of powerful FR-II radio galaxies at GHz and MHz frequencies and show for the first time their small-scale spectral structure. We highlight problems in traditional methods of analysis and demonstrate how these issues can now be addressed. We present the latest results from low frequency studies which suggest a potential increase in the total energy content of radio galaxy lobes with possible implications for the energetics of the population as a whole.

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Keywords : acceleration of particles – radiation mechanisms: non-thermal – methods: data analysis – galaxies: jets – radio continuum: galaxies – galaxies: active