Simple Model of the Outflow from Starburst Galaxies: Application to Radio Observations

We present an analytical model for the hydrodynamic outflow from the disk of a starburst galaxy. The model is used to calculate the cosmic ray propagation and the radio intensity distribution in the nuclear starbust region of NGC 253. We find that the cosmic ray energy production rate of the central 600 pc of NGC 253 is about $3\cdot 10^{41}$ erg s$^{-1}$, that is about 15 percent of the total mechanical supernova power. For this inner region we estimate a terminal outflow velocity of 900 km s$^{-1}$ and a mass loss rate of $\dot{M}=2\div 4M_\odot$ per year.