Cosmic Rays in M82: Testing the Calorimeter Model
American Astronomical Society, AAS Meeting #220, #434.03
Published in May 2012
From first principles, we construct a simple model for the evolution of energetic particles in the starburst galaxy M82. Assuming constant cosmic-ray acceleration efficiency with Milky Way parameters, we calculate the cosmic-ray proton and primary & secondary electron/positron populations. From the cosmic-ray spectra, we can predict the radio synchrotron and gamma-ray spectrum. To more accurately model the radio spectrum, we incorporate a multiphase interstellar medium in the starburst region of M82. The interstellar medium is highly fragmented with compact dense molecular clouds and dense ionized gas, both embedded in a hot, low density medium in overall pressure equilibrium. The spectra for this simple model are compared to the observed radio and gamma-ray spectra of M82. Chi-squared tests are used to compare with radio observations to find the best-fit parameters. The best-fit model yields constraints on the magnetic field strength for the starburst zone in M82. Through this project, we aim to check the calorimeter model, in which energetic particles lose most of their energy within the galaxy, and build a better understanding of the radio-FIR correlation in starburst galaxies.
(c) 2012: American Astronomical Society