Data-driven extrapolation schemes of Fermi-LAT spectra to the VHE

TL;DR

This paper introduces a data-driven approach to evaluate and improve the reliability of extrapolation methods used to predict very high energy spectra from Fermi-LAT data, aiding the identification of VHE gamma-ray sources.

Contribution

It presents a novel methodology that tests and assesses the accuracy of existing VHE extrapolation schemes using real observational data from gamma-ray catalogs.

Findings

The methodology effectively distinguishes more reliable extrapolation schemes.

It highlights the limitations of simple analytical functions in VHE spectrum prediction.

The approach enhances the interpretation of Fermi-LAT data for VHE gamma-ray studies.

Abstract

After 10 years of operations of the Large Area Telescope (LAT), a high-energy pair-creation telescope onboard the Fermi satellite, the Fermi Collaboration has produced two major catalogs: the 4FGL and the 3FHL. These catalogs represent the best sample of potential very high energy (VHE) emitters that may be studied by Imaging Atmospheric Cherenkov Telescopes (IACTs). Several methods are used to extrapolate the Fermi-LAT spectra to TeV energies, generally using simple analytical functions. The recent success of IACTs has motivated the creation of catalogs listing the discoveries of these experiments. Among these initiatives, gamma-cat excels as an open-access tool to archive high-level results in the VHE field, such as catalogs, spectra and light curves. By using these resources, we present a data-driven methodology to test the reliability of different VHE extrapolation schemes used in the literature and evaluate their accuracy reproducing real VHE observations.