G. Di Bernardo | Searcharxiv

arXiv2013

Galactic electron and positron properties from cosmic ray and radio observations

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.

astro-ph.HE↗

arXiv2009

On possible interpretations of the high energy electron-positron spectrum measured by the Fermi Large Area Telescope

The Fermi-LAT experiment recently reported high precision measurements of the spectrum of cosmic-ray electrons-plus-positrons (CRE) between 20 GeV and 1 TeV. The spectrum shows no prominent spectral features, and is significantly harder than that inferred from several previous experiments. Here we discuss several interpretations of the Fermi results based either on a single large scale Galactic CRE component or by invoking additional electron-positron primary sources, e.g. nearby pulsars or particle Dark Matter annihilation. We show that while the reported Fermi-LAT data alone can be interpreted in terms of a single component scenario, when combined with other complementary experimental results, specifically the CRE spectrum measured by H.E.S.S. and especially the positron fraction reported by PAMELA between 1 and 100 GeV, that class of models fails to provide a consistent interpretation. Rather, we find that several combinations of parameters, involving both the pulsar and dark matter scenarios, allow a consistent description of those results. We also briefly discuss the possibility of discriminating between the pulsar and dark matter interpretations by looking for a possible anisotropy in the CRE flux.

astro-ph.HE↗