Active Galactic Nuclei
Supermassive accreting black holes at the center of galaxies, called Active Galactic Nuclei (AGN) are the more powerful non-transient objects in the Universe, emitting from the radio to the gamma-rays. Among them, an extreme class of AGN with a jet are the brightest one.
The experiments
The very high-energy astrophysics domain covering the study of jetted AGN of blazar type have made significant progress in the last decade with γ -ray observations from the Fermi-LAT telescope. Operating since 2008, the last Fermi-LAT catalogue covering 8 years of observations, contains about 3,000 AGN in the energy range 50MeV to 1TeV.
The Data
In order to understand the full range of physical processes taking place around these powerful AGN, gamma-rays should be combined with observations at lower-frequency, from radio to X-rays.
The analyses
From multiwavelength observations, one can study the spectral energy distributions (SEDs) of blazars. They are dominated by beamed jet emission and take the form of two broad non-thermal components, one at low energies, peaking in the radio through optical, and one at high energies, peaking in the–rays. The modelling of the broadband emission of blazars allows one to get insight on the physics of the jet.
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