Cosmic rays and non-thermal emission in simulated galaxies ? I. Electron and proton spectra compared to Voyager-1 data

Current-day cosmic ray (CR) propagation studies use static Milky-Way models and fit parametrized source distributions to data. Instead, we three-dimensional magneto-hydrodynamical (MHD) simulations of isolated galaxies with the moving-mesh code AREPO that self-consistently accounts for hydrodynamic effects CR protons. In post-processing, calculate their steady-state spectra, taking into account all relevant loss processes. We show this assumption is well justified in disc generally regions emit non-thermal radio gamma rays. Additionally, model spectra primary electrons, accelerated by supernova remnants, secondary electrons positrons produced hadronic proton interactions gas. find above 10 GeV only weakly depend on galactic radius, while they acquire a radial dependence at lower energies due Coulomb interactions. Radiative losses steepen central diffusive dominate outskirts. Secondary exhibit steeper spectrum than primaries because originate from transported spectra. Consistent Voyager-1 AMS-02 data, our (i) turn-over below so start total particle (ii) match shape positron fraction up GeV. conclude modeling MHD-CR galaxy sufficiently realistic capture dominant transport shaping arguing full MHD treatment accurately future.