Galactic electron and positron properties from cosmic ray and radio observations

TL;DR

This paper models cosmic ray electrons, positrons, and Galactic radio emissions, successfully reproducing data from 1 GeV to 1 TeV, and constrains cosmic-ray propagation parameters including the halo height.

Contribution

It provides a comprehensive model that simultaneously fits cosmic ray and radio data, revealing the need for an extra component at high energies and constraining the Galactic halo size.

Findings

Electron primary spectrum must be suppressed below a few GeV.

An extra hard component is needed above 10 GeV.

A thin halo ($z_t \,\lsim\, 2\,\text{kpc}$) is excluded.

Abstract

We perform a consistent modeling of cosmic ray electrons, positrons and of the radio emission of the Galaxy. For the time we reproduce all relevant data sets between 1 GeV and 1 TeV including the recent AMS-02 positron fraction results. We show that below few GeV cosmic ray and radio data require that electron primary spectrum to be drastically suppressed and the propagated spectrum be dominated by secondary particles. Above 10 GeV an electron + positron extra-component with a hard spectrum is required. The positron spectrum measured below few GeV is consistently reproduced only within low reacceleration models. We also constrain the scale-height of the cosmic-ray distribution showing that a thin halo ($z_t \lsim 2 \kpc$) is excluded.