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Unveiling particle acceleration and radiative processes in low-power hotspots of radio galaxies
Giulia Migliori (IRA)
Tuesday 21/01/2020 @ 14:00, Sala IV piano Battiferro
Hotspots are bright and compact regions located at the edge of powerful Fanaroff-Riley type II radio galaxies. In the standard scenario, particles are accelerated by a single strong shock at the jet termination and produce radio to X-ray radiation. However, this simple picture is challenged by a number of observations. In particular, the discovery of optical, diffuse emission, extending on kpc-scales, can be hardly reconciled with the short radiative lifetimes of the optical-emitting particles. This suggests that efficient and spatially distributed acceleration mechanisms could be active in the post-shock region. Moreover, the spatial offsets, which are often measured between the peaks of the radio and X-ray emission, cannot be easily explained by one-zone leptonic models. We present the results of our multi-wavelength campaign on a small sample of hot spots of the 3C catalogue. The high-sensitivity JVLA, near-infrared and optical observations allowed us to probe the small-scale structure of the hot spots, unveiling the presence of compact (<hundreds pc) features, and to resolve the distribution of the magnetic field within the hot spot. We discuss the implications of these findings within the framework of the mechanisms accelerating particles and producing the broadband radio-to-X-ray hot spot emission.