Isotropic extragalactic flux from dark matter annihilations: lessons from interacting dark matter scenarios

TL;DR

This paper investigates how alternative dark matter models with suppressed low-mass structures affect the extragalactic gamma-ray and neutrino signals, showing that these models produce similar spectral shapes to LambdaCDM but with reduced flux, potentially misleading interpretations.

Contribution

It demonstrates that non-standard dark matter scenarios can mimic LambdaCDM spectral shapes with lower flux, impacting the interpretation of extragalactic signals.

Findings

Spectral shape remains similar across models

Flux normalization is reduced in alternative models

Potential for misinterpreting dark matter annihilation signals

Abstract

The extragalactic gamma-ray and neutrino emission may have a contribution from dark matter (DM) annihilations. In the case of discrepancies between observations and standard predictions, one could infer the DM pair annihilation cross section into cosmic rays by studying the shape of the energy spectrum. So far all analyses of the extragalactic DM signal have assumed the standard cosmological model (LambdaCDM) as the underlying theory. However, there are alternative DM scenarios where the number of low-mass objects is significantly suppressed. Therefore the characteristics of the gamma-ray and neutrino emission in these models may differ from LambdaCDM as a result. Here we show that the extragalactic isotropic signal in these alternative models has a similar energy dependence to that in LambdaCDM, but the overall normalisation is reduced. The similarities between the energy spectra combined with the flux suppression could lead one to misinterpret possible evidence for models beyond LambdaCDM as being due to CDM particles annihilating with a much weaker cross section than expected.