Detecting extended gamma-ray emission with the next generation Cherenkov telescopes

TL;DR

This paper explores the potential of next-generation Cherenkov telescopes to detect extended gamma-ray emissions caused by electromagnetic cascades from blazars, which can inform cosmological models of the universe.

Contribution

It introduces a simulation-based method to assess the detectability of gamma-ray halos with future Cherenkov telescopes, considering various intergalactic magnetic field strengths.

Findings

Simulated electromagnetic cascades for different IGMF strengths.

Developed a statistical method to evaluate detection feasibility.

Provided predictions for future telescope observations.

Abstract

Very high energy (VHE $>$100 GeV) gamma rays coming from blazars can produce pairs when interacting with the Extragalactic Background Light (EBL) and the Cosmic Microwave Background, generating an electromagnetic cascade. Depending on the Intergalactic Magnetic Field (IGMF) intensity, this cascade may result in an extended isotropic emission of photons around the source (halo), or in a broadening of the emission beam. The detection of these effects might lead to important constrains both on the IGMF intensity and the EBL density, quantities of great relevance in cosmological models. Using a Monte Carlo program, we simulate electromagnetic cascades for different values of the IGMF intensities and coming from a source similar to 1ES0229+200, a blazar with hard intrinsic spectrum at redshift $z=0.14$, which is an ideal distance for potentially observing the effect. We study the possible response of a generic future Cherenkov telescope using a simplified model for the sensitivity, effective area and angular resolution. Finally, combining these instrument properties, we calculate the angular distribution of photons and develop a method to test the statistical feasibility of detecting the effect in the near future.