Impact of local foreground radiations on Very High Energy observations of extragalactic sources

TL;DR

This paper examines how local foreground radiations from host galaxies and the Milky Way can affect Very High Energy gamma-ray observations of extragalactic sources, highlighting potential contamination issues.

Contribution

It models and analyzes local radiative foregrounds' impact on VHE observations, emphasizing their significance mainly for nearby active galactic nuclei.

Findings

Foreground radiations can significantly affect local sources like Centaurus A.

Distant sources such as M87 are less impacted by local foregrounds.

Implications for interpreting VHE gamma-ray data in cosmological studies.

Abstract

In the framework of exploiting Very High Energy (VHE) gamma-ray observations of extragalactic sources to infer constraints on the intensity of cosmological background radiations, as well as on deviations from the standard model of particles and physical interactions (like violations of Lorentz invariance and axion-like particles -- LIV and ALPs), we discuss here possible contaminant effects due to the presence of radiations fields from local sources. We specifically model and analyze the foreground radiations produced inside the host galaxy of the VHE source and the cosmic environment itself hosting the source, as well as radiations produced in the Milky Way, along the VHE source's observational line-of-sights. Our analysis shows that such contaminant foregrounds may indeed impact on observations of only the very local Active Galactic Nuclei (e.g. Centaurus A), but not significantly those in the Virgo cluster (M87) and beyond.