Studies of active galactic nuclei with CTA
Abstract
In this paper, we review the prospects for studies of active galactic nuclei (AGN) using the envisioned
future Cherenkov Telescope Array (CTA). This review focuses on jetted AGN, which constitute the vast
majority of AGN detected at gamma-ray energies. Future progress will be driven by the planned lower
energy threshold for very high energy (VHE) gamma-ray detections to 10 GeV and improved flux sensitivity
compared to current-generation Cherenkov Telescope facilities. We argue that CTA will enable
substantial progress on gamma-ray population studies by deepening existing surveys both through
increased flux sensitivity and by improving the chances of detecting a larger number of low-frequency
peaked blazars because of the lower energy threshold. More detailed studies of the VHE gamma-ray spectral
shape and variability might furthermore yield insight into unsolved questions concerning jet formation
and composition, the acceleration of particles within relativistic jets, and the microphysics of the
radiation mechanisms leading to the observable high-energy emission. The broad energy range covered
by CTA includes energies where gamma-rays are unaffected from absorption while propagating in the
extragalactic background light (EBL), and extends to an energy regime where VHE spectra are strongly
distorted. This will help to reduce systematic effects in the spectra from different instruments, leading
to a more reliable EBL determination, and hence will make it possible to constrain blazar models up to
the highest energies with less ambiguity.