Radio data and synchrotron emission in consistent cosmic ray models

TL;DR

This paper demonstrates that consistent cosmic ray and synchrotron emission models constrain the size of the galactic diffusion halo, impacting dark matter search strategies.

Contribution

It introduces a comprehensive model linking cosmic-ray propagation with synchrotron emission, constraining halo sizes based on multi-frequency radio data.

Findings

Models agree with cosmic-ray and radio data across frequencies.

Very large or very small halo sizes are strongly disfavored.

Implications for dark matter indirect detection are significant.

Abstract

It is well established that phenomenological two-zone diffusion models of the galactic halo can very well reproduce cosmic-ray nuclear data and the observed antiproton flux. Here, we consider lepton propagation in such models and compute the expected galactic population of electrons, as well as the diffuse synchrotron emission that results from their interaction with galactic magnetic fields. We find models in agreement not only with cosmic ray data but also with radio surveys at essentially all frequencies. Requiring such a globally consistent description strongly disfavors very large ($L\gtrsim 15$ kpc) and, even stronger, small ($L\lesssim 1$ kpc) effective diffusive halo sizes. This has profound implications for, e.g., indirect dark matter searches.