TeV blazars and their distance

TL;DR

This paper refines a method to estimate the distances of TeV blazars by analyzing their gamma-ray spectra in the GeV and TeV regimes, improving accuracy with updated data and models.

Contribution

It updates and tests a spectral absorption method for determining blazar distances using recent spectra and EBL models, applied to previously unknown sources.

Findings

Enhanced distance constraints for blazars using updated spectra.

Validation of the method with recent EBL models.

Application to new VHE blazars with unknown redshift.

Abstract

Recently, a new method to constrain the distance of blazars with unknown redshift using combined observations in the GeV and TeV regimes has been developed, with the underlying assumption that the Very High Energy (VHE) spectrum corrected for the absorption of TeV photons by the Extragalactic Background Light (EBL) via photon-photon interaction should still be softer than the gamma-ray spectrum observed by Fermi/LAT. The constraints found are related to the real redshifts by a simple linear relation, that has been used to infer the unknown distance of blazars. The sample will be revised with the up-to-date spectra in both TeV and GeV bands, the method tested with the more recent EBL models and finally applied to the unknown distance blazars detected at VHE.