Recent measurements of the synchrortron emission of the external galaxy M51 give indirect implication for the cosmic-ray electron (CRE) transport in the interstellar medium.
By modelling the CRE transport considering all relevant energy loss processes we aim to distinguish the contribution of diffusive and advective transport. The current measurements give insights in the diffusion coefficient, the star formation rate and the magnetic field strength.
Using these information we use the CRPropa module
DiffusionSDE to solve the 3D transport equation for isotropic diffusion and the 3D-advection profile. Additionally we implement the relevant energy loss processes as a continues loss.
With our best fit model the data can be described well. For the best fit the wind speed followed from the observation of the star formation rate must be decreased by a factor 5. We find that the inner galaxy is dominated by advection and the outer by spatial diffusion.
In general leads this approach of modelling face-on galaxies insights of the only indirect observable advection profile.