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Cosmic rays (CRs) and magnetic fields may be dynamically important in drivinglarge-scale galactic outflows from rapidly star-forming galaxies. We constructtwo-dimensional axisymmetric models of the local starburst and super-windgalaxy M82 using the CR propagation code GALPROP. Using prescribed gas densityand magnetic field distributions, wind profiles, CR injection rates, andstellar radiation fields, we simultaneously fit both the integrated gamma-rayemission and the spatially-resolved multi-frequency radio emission extendedalong M82's minor axis. We explore the resulting constraints on the gasdensity, magnetic field strength, CR energy density, and the assumed CRadvection profile. In accord with earlier one-zone studies, we generically findlow central CR pressures, strong secondary electron/positron production, and animportant role for relativistic bremsstrahlung losses in shaping thesynchrotron spectrum. We find that the relatively low central CR densityproduces CR pressure gradients that are weak compared to gravity, stronglylimiting the role of CRs in driving M82's fast and mass-loaded galacticoutflow. Our models require strong magnetic fields and advection speeds oforder ~1000 km/s on kpc scales along the minor axis in order to reproduce theextended radio emission. Degeneracies between the controlling physicalparameters of the model and caveats to these findings are discussed.

Cosmic Rays and Magnetic Fields in the Core and Halo of the Starburst M82: Implications for Galactic Wind Physics