Weekly seminars

Multi-messenger approach for the interpretation of cosmic electron and positron fluxes

by Mattia Di Mauro (Catholic University of America, Department of Physics)

auditorium (LAPTh)



9 chemin de Bellevue 74940 Annecy

Different experiments on satellite (such as AMS-02, CALET, DAMPE and Fermi-LAT) and on the ground (such as HESS) have provided precise measurements for the flux of cosmic electrons and positrons. These data cover about 4 orders of magnitude, between 0.1 GeV to multi TeV, and reach uncertainties as low as a few percent. This represents an incredibly rich dataset to study the cosmic-ray emission mechanisms from Galactic sources, mainly pulsar wind nebulae (PWNe) and supernova remnants (SNRs), the cosmic-ray propagation in the Galaxy and to study new Physics, for example the interaction of dark matter particles.

In my presentation, I will show the latest results for a multi messenger-approach applied to the interpretation of the flux of cosmic electrons and positrons. In particular, I will first display how, using the radio data from individual SNRs, we are able to demonstrate that the a significant flux of electrons above 100 GeV is due to the bright Vela Cygnus SNRs.

Then, I will use the latest measurements by HAWC, Fermi-LAT and HESS for the gamma-ray emission around PWNe to derive their injection spectrum of positrons. Indeed, the gamma-ray emission around PWNe can be interpreted as positrons and electrons accelerated from a PWN and inverse Compton scattering on the Galactic interstellar radiation fields. I will show that the morphology of the gamma-ray emission for the PWNe in our sample is compatible with a diffusion coefficient around these sources that is about two orders of magnitude lower than the average value in the Galaxy. This result could lead to important consequences for the existing models of CR propagation.

Finally, I will present that, given the current observations for GeV-TeV photons around PWNe, the cumulative positron flux from these sources is compatible with the positron flux above 10 GeV.


This presentation is based on the following papers:

arXiv:1908.03216, arXiv:1903.05699, arXiv:1903.05647, arXiv:1803.01009