Spectral trends in the Very High Energy blazar sample due to EBL absorption

TL;DR

This study investigates whether the lack of observed spectral softening in VHE blazars with redshift can be explained by EBL absorption effects, through simulations of blazar populations and detection criteria.

Contribution

It introduces simulation-based analysis to explore if intrinsic blazar properties can account for the absence of expected spectral trends due to EBL absorption.

Findings

No evident spectral-softening trend with redshift in current VHE blazar data.

Simulations show that certain intrinsic property distributions can reproduce observations.

Detection criteria influence the observed spectral properties and their correlation with redshift.

Abstract

The absorption of gamma-rays in the intergalactic medium due to the EBL (Extragalactic Background Light) causes the observed blazar spectrum to be fainter and softer than their intrinsic state. It could thus be expected to see an effective spectral-softening trend with redshift. No such trend is evident in the sample of VHE blazars currently observed. To check which distributions of the properties of the parent blazar population could reproduce the observations, various simulations are done. The resulting subsamples that satisfy a generic detection criterion for the current generation of ACTs (Atmospheric Cherenkov Telescope) are checked to identify whether any inherent correlations (of spectral properties with redshift) are required to explain the current observations.