Radio galaxies from Fermi to the CTA
Résumé
We present the results of a study aimed at evaluating the impact of the CTA in high-energy studies of radio galaxies, and elusive class of high-energy and very-high-energy emitters, which counts only 5 detections in the TeV band at the moment. We perform simulations of CTA observations of the Fermi-LAT radio galaxies using the ctools package. Our simulations indicate that 7 out of 12 local (z<0.1) candidates should be detected in 50 hours of CTA integration time, if the Fermi and the CTA power-laws are smoothly connected. If the spectrum drops off in the TeV band, the number of detections progressively decreases shifting the power-law cutoff to lower energies. Given the elusiveness of radio galaxies at TeV energies, we suggest a CTA observing strategy based on long targeted observations. A blind-sky large area survey implies insufficient integrating time per FoV, but it will be suitable for discovering flaring sources or extremely high-energy peaked radio galaxies that are faint in the Fermi band (and therefore not part of the sample studied here) but observable in the TeV band. Finally we present a diagnostic plot useful to verify whether an AGN with given flux and power-law slope in the Fermi band could be a good target for CTA observations.