Global Cosmic-ray-related Luminosity and Energy Budget of the Milky Way

Abstract

We use the GALPROP code for cosmic-ray (CR) propagation to calculate the broadband luminosity spectrum of the Milky Way related to CR propagation and interactions in the interstellar medium. This includes γ-ray emission from the production and subsequent decay of neutral pions (π^0), bremsstrahlung, and inverse Compton scattering, and synchrotron radiation. The Galaxy is found to be nearly a CR electron calorimeter, but only if γ-ray emitting processes are taken into account. Synchrotron radiation alone accounts for only one-third of the total electron energy losses with ~10%-20% of the total synchrotron emission from secondary CR electrons and positrons. The relationship between far-infrared and radio luminosity that we find from our models is consistent with that found for galaxies in general. The results will be useful for understanding the connection between diffuse emissions from radio through γ-rays in "normal" (non-active galactic nucleus dominated) galaxies as well as for estimating the broadband extragalactic diffuse background from these kinds of galaxies.

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