Prospects for Very High Energy Blazar Survey by the Next Generation Cherenkov Telescopes

TL;DR

This paper evaluates the potential of next-generation Cherenkov telescopes like CTA to survey VHE blazars, predicting detection rates, follow-up strategies, and methods to constrain the extragalactic background light using blazar observations.

Contribution

It introduces an improved VHE spectral energy distribution model and assesses survey strategies and EBL constraints with upcoming gamma-ray telescopes.

Findings

A 100-hour CTA survey could detect about 3 VHE blazars.

Wider, shallower surveys increase detection numbers.

VHE blazar spectra can constrain the extragalactic background light.

Abstract

The prospects for future blazar surveys by next-generation very high energy (VHE) gamma-ray telescopes, such as Advanced Gamma-ray Imaging System (AGIS) and Cherenkov Telescope Array (CTA), are investigated using the latest model of blazar luminosity function and its evolution which is in good agreement with the flux and redshift distribution of observed blazars as well as the extragalactic gamma-ray background. We extend and improve the template of spectral energy distributions (SEDs) based on the blazar SED sequence paradigm, to make it reliable also in the VHE bands (above 100 GeV) by comparing with the existing VHE blazar data. Assuming the planned CTA sensitivities, a blind survey using a total survey time of ~100 hrs could detect ~3 VHE blazars, with larger expected numbers for wider/shallower surveys. We also discuss following-up of Fermi blazars. Detectability of VHE blazars in the plane of Fermi flux and redshift is presented, which would be useful for future survey planning. Prospects and strategies are discussed to constrain the extragalactic background light (EBL) by using the absorption feature of brightest blazar spectra, as well as cut-offs in the redshift distribution. We will be able to get useful constraints on EBL by VHE blazars at different redshifts ranging 0.3-1 TeV corresponding to z=0.10-0.36.