Revisiting the TeV detection prospects for radio galaxies

Abstract

Radio galaxies host relativistic jets oriented away from our line of sight, making them challenging targets for Very High Energy (VHE, E$>$100 GeV) $\gamma$-ray detectors. Indeed, out of $\sim 100$ extragalactic sources detected at $E>100$ GeV, only six are radio galaxies. The new Cherenkov Telescope Array (CTA) will provide order-of-magnitude improvements in sensitivity with respect to the present generation of ground-based $\gamma$-ray observatories, opening new frontiers for high-energy studies of radio galaxies. In a previous paper, we studied the CTA detection prospects of misaligned jets from the Third Fermi-LAT catalog (3FGL) sample. In this work, we take advantage of the expanded sample from the Fourth Fermi-LAT catalog (4FGL), including roughly double the number of sources. We simulate CTA observations of 41 $\gamma$-ray radio galaxies, extrapolating their GeV spectrum into the TeV range assuming different spectral shapes. We predict that the CTA will detect eleven new TeV radio galaxies with an observational campaign of 50 hours per source, under the realistic assumption of a spectral cutoff at 0.5 TeV. This would increase the sample of VHE radio galaxies by a factor of three, and result in the first detection of FR II radio galaxies at these energies. By simulating CTA observations with 5 hours exposure, we predict that two Fermi-LAT radio galaxies should already be within reach of current TeV observatories. Finally we have investigated the prospects for a CTA detection of extended VHE emission from the lobe-dominated FR I Fornax A, and predict that this will be possible for integration times $\gtrsim 50$ hours. We conclude that the CTA will significantly impact our understanding of misaligned jets at TeV energies, allowing us to perform population studies and compare the two main radio galaxy subclasses for the first time in this energy band.

Accepted for publication in Astroparticle Physics. 19 pages (main text 11 pages), 3 figures, 4 tables

References in corpus (2)

• Fermi Gamma-ray Imaging of a Radio Galaxy
• GammaLib and ctools: A software framework for the analysis of astronomical gamma-ray data

Cited by in corpus (4)

• High energy emission component, population, and contribution to the extragalactic gamma-ray background of gamma-ray emitting radio galaxies
• General Physical Properties of Gamma-Ray-emitting Radio Galaxies
• A New Gamma-ray Emitting Population of FR0 Radio Galaxies
• IGR J18249-3243: a new GeV-emitting FR II and the emerging population of high energy radio galaxies