The Contribution From TeV Halos to the Isotropic Gamma-Ray Background

TL;DR

This paper models the gamma-ray emission from TeV halos around pulsars in Andromeda and estimates their significant contribution, up to 20%, to the high-energy isotropic gamma-ray background observed on Earth.

Contribution

It provides the first detailed prediction of TeV halo contributions to the isotropic gamma-ray background and assesses their detectability by upcoming gamma-ray observatories.

Findings

TeV halos contribute up to ~20% of the gamma-ray background above 0.1 TeV.

Predicted gamma-ray signals from Andromeda's TeV halos are detectable by CTA.

TeV halos are a significant component of the Milky Way's gamma-ray emission.

Abstract

Recent observations have shown that pulsars are surrounded by extended regions which emit TeV-scale gamma rays through the inverse Compton scattering of very high energy electrons and positrons. Such TeV halos are responsible for a large fraction of the Milky Way's TeV-scale gamma-ray emission. In this paper, we calculate the gamma-ray spectrum from the population of TeV halos located within the Andromeda Galaxy, predicting a signal that is expected to be detectable by the Cherenkov Telescope Array (CTA). We also calculate the contribution from TeV halos to the isotropic gamma-ray background (IGRB), finding that these sources should contribute significantly to this flux at the highest measured energies, constituting up to $\sim 20\%$ of the signal observed above $\sim 0.1 \, {\rm TeV}$.