Blazars distance indications from Fermi and TeV data
Abstract
A new method to constrain the distance of blazars with unknown redshift using combined observations in the GeV and TeV regimes will be presented. The underlying assumption is 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 extrapolation of the gamma-ray spectrum observed by Fermi/LAT. Starting from the observed spectral data at VHE, the EBL-corrected spectra are derived as a function of the redshift z and fitted with power laws. Comparing the redshift dependent VHE slopes with the power law fits to the LAT data an upper limit to the source redshift can be derived. The method is applied to all TeV blazars detected by LAT with known distance and an empirical law describing the relation between the upper limits and the true redshifts is derived. This law can be used to estimate the distance of unknown redshift blazars: as an example, the distance of PKS 1424+240 is inferred.
Cite
@article{arxiv.1101.4098,
title = {Blazars distance indications from Fermi and TeV data},
author = {Elisa Prandini and Giacomo Bonnoli and Laura Maraschi and Mose' Mariotti and Fabrizio Tavecchio},
journal= {arXiv preprint arXiv:1101.4098},
year = {2022}
}
Comments
Contribution to SciNeGHE 2010, Trieste, Italy, September 2010; 4 pages, 2 figure