Potential of EBL and cosmology studies with the Cherenkov Telescope Array

TL;DR

This paper discusses how the Cherenkov Telescope Array (CTA) will enhance our understanding of the extragalactic background light (EBL) by observing distant gamma-ray sources, including AGNs and gamma-ray bursts, with improved sensitivity and energy coverage.

Contribution

It analyzes the potential of CTA to improve constraints on EBL density and sources through detailed spectra of AGNs and GRBs at various redshifts.

Findings

CTA will detect a large sample of AGNs across different redshifts.

CTA's sensitivity will allow better constraints on EBL density.

Gamma-ray bursts can serve as probes for high-redshift EBL studies.

Abstract

Very high energy (VHE, E >100 GeV) gamma-rays are absorbed via interaction with low-energy photons from the extragalactic background light (EBL) if the involved photon energies are above the threshold for electron-positron pair creation. The VHE gamma-ray absorption, which is energy dependent and increases strongly with redshift, distorts the VHE spectra observed from distant objects. The observed energy spectra of the AGNs carry, therefore, an imprint of the EBL. The detection of VHE gamma-ray spectra of distant sources (z = 0.11 - 0.54) by current generation Imaging Atmospheric Cherenkov Telescopes (IACTs) enabled to set strong upper limits on the EBL density, using certain basic assumptions about blazar physics. In this paper it is studied how the improved sensitivity of the Cherenkov Telescope Array (CTA) and its enlarged energy coverage will enlarge our knowledge about the EBL and its sources. CTA will deliver a large sample of AGN at different redshifts with detailed measured spectra. In addition, it will provide the exciting opportunity to use gamma ray bursts (GRBs) as probes for the EBL density at high redshifts.