Predictions of TeV emission for a set of hard BL Lac objects

TL;DR

This study predicts TeV gamma-ray emission from 55 hard-spectrum BL Lac objects by extrapolating Fermi data, accounting for extragalactic background light absorption, and assessing their detectability with current and upcoming Cherenkov telescopes.

Contribution

It provides the first systematic prediction of VHE emission for a specific set of BL Lac objects considering redshift-dependent absorption effects.

Findings

Many candidates are promising for detection with the Cherenkov Telescope Array.

Extrapolated spectra suggest significant TeV emission in several sources.

Absorption effects strongly influence the detectability predictions.

Abstract

We focus our analysis on 55 BL Lac objects with a hard Fermi gamma-ray spectrum, and for which a redshift or a lower limit to it has been determined by a previous study of ours. We extrapolate the spectral fits given by the 4FGL catalogue to the VHE band (>0.1 TeV), which can be explored by imaging atmospheric Cherenkov telescopes. Furthermore, we take into account the absorption due to the extragalactic background light, strongly depending on the redshift. Finally, we compare our results with publicly available sensitivity curves for a selection of imaging atmospheric Cherenkov telescope arrays currently operating or under construction. From our extrapolations and simulations we find a large number of promising candidates for observation with the forthcoming Cherenkov Telescope Array observatory.