The high-energy view of young radio sources: X-ray and gamma-ray observations

According to theoretical predictions, young extragalactic radio sources may release a significant fraction of their total radiative power in the high-energy domain. X-ray emission is expected from the central active galactic nucleus (AGN), and from the extended radio components, jet, hot spots, and lobes. The X-rays should also trace the interactions of the radio source with its environment, and reveal to us how the young source clears its way out of the host galaxy and finally reaches the giant stage. Observational campaigns with Chandra and XMM-Newton telescopes have confirmed that young radio sources are indeed relatively X-ray luminous. Recently, efforts have been undertaken to obtain a complete X-ray view of the whole population of young sources, focusing on the youngest and faintest objects. At the same time, the study of the X-ray properties of the samples of quasars and galaxies provides us with clues on the nature of the observed high-energy emission. In specific cases, X-ray and multi-wavelength data allow for a direct test of the different models. A detection in the y-ray band would represent a robust proof of a non-thermal, high-energy component and the launch of the Fermi telescope has opened the hunt to young radio sources in the y-ray window. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)