Theoretical indication of a possible asymmetry in gamma-radiation between Andromeda halo hemispheres due to Compton scattering on electrons from their hypothetical sources in the halo

TL;DR

This paper explores the potential asymmetry in gamma-ray emissions between the two hemispheres of the Andromeda galaxy caused by Compton scattering of electrons from dark matter decay or annihilation, which could be detectable by experiments.

Contribution

It provides a theoretical estimate of gamma-ray asymmetry in Andromeda's halo due to inverse Compton scattering, considering the galaxy's orientation and potential dark matter sources.

Findings

Asymmetry could reach several 10% in gamma-ray energies between hemispheres.

The effect depends on the galaxy's inclination and electron distribution in the halo.

Potential observability by gamma-ray experiments.

Abstract

Dark matter (DM) can give observable effects decaying or annihilating with production of electrons or/and photons. Such probability was widely researched for our Galaxy. Here we consider one aspect of similar effect for Andromeda galaxy. We explicitly estimate the energy of the photon of the medium experiencing Inverse Compton (IC) scattering off electron in halo. These photons can be registered by different experiments. Dark matter annihilation or decay could be the source of high energy electrons in halo, though the source could be of other origins too (e.g. running neutron stars). Because of specifics in space orientation of Andromeda galaxy disk (a little inclined to the line of sight), the difference in energies could arise for the photons from two hemispheres of Andromeda halo. It is obtained that such asymmetry can be at the level of several 10%.