Comparison of the expected and observed supernova remnant counts with Fermi/LAT

Ie Vovk,A Neronov,D Malyshev

doi:10.1051/epjconf/201510504001

Abstract

SNRs are commonly believed to be the accelerators of the galactic cosmic rays – mainly protons – and are expected to produce γ-rays through the inelastic proton-proton collisions. Fermi/LAT was expected to detect many of those, but only a dozen is listed in the recent Fermi/LAT 2nd Source catalogue. To test whether the observed number of SNRs is in agreement with the above assumption, we use a simplified model of an SNR and calculate the predicted amount of the observable remnants taking into account their distribution in the Galaxy and the sensitivity of Fermi/LAT. We find that the observed number of SNRs agrees with the prediction of our model if we assume a low, ≪ 1 cm−3, number density of the SNR's ambient medium. The result, presented here, suggests, that on average the supernova explosions happen in the under-dense regions, such as bubbles, creating by the winds of the progenitor stars. Under this natural supposition our result finds an agreement with the assumption, that the observed population of supernovae remnants is indeed responsible for the production of the galactic cosmic rays.

Highlights

The supernova remnants (SNRs) – expanding gas shells, resulting from the explosion of the supernovae – are widely observed in the Galaxy
Under this natural supposition our result finds an agreement with the assumption, that the observed population of supernovae remnants is responsible for the production of the galactic cosmic rays
The exact origin of the galactic cosmic rays is not known, for decades the SNRs were favoured as their sources due to their energy budget and number in the Galaxy [e.g. 2–4], alternative models of the Cosmic Rays (CR) production exist [5], related to the acceleration by pulsars and/or pulsar wind nebulae [6] or in the larger scale OB associations [e.g. 7, 8]

Summary

Introduction

The supernova remnants (SNRs) – expanding gas shells, resulting from the explosion of the supernovae – are widely observed in the Galaxy. To test whether the observed number of SNRs is in agreement with the above assumption, we use a simplified model of an SNR and calculate the predicted amount of the observable remnants taking into account their distribution in the Galaxy and the sensitivity of Fermi/LAT.

Results

Conclusion