ACTIVE GALACTIC NUCLEI, NEUTRINOS, AND INTERACTING COSMIC RAYS IN NGC 253 AND NGC 1068

Abstract

The galaxies M82, NGC 253, NGC 1068, and NGC 4945 have been detected in\ngamma-rays by Fermi. Previously, we developed and tested a model for cosmic ray\ninteractions in the starburst galaxy M82. Now, we aim to explore the\ndifferences between starburst and active galactic nuclei (AGN) environments by\napplying our self-consistent model to the starburst galaxy NGC 253 and the\nSeyfert galaxy NGC 1068. Assuming constant cosmic-ray acceleration efficiency\nby supernova remnants with Milky-Way parameters, we calculate the cosmic-ray\nproton and primary and secondary electron/positron populations, predict the\nradio and gamma-ray spectra, and compare with published measurements. We find\nthat our models easily fits the observed gamma-ray spectrum for NGC 253 while\nconstraining the cosmic ray source spectral index and acceleration efficiency.\nHowever, we encountered difficultly modeling the observed radio data and\nconstraining the speed of the galactic wind and the magnetic field strength,\nunless the gas mass is less than currently preferred values. Additionally, our\nstarburst model consistently underestimates the observed gamma-ray flux and\noverestimates the radio flux for NGC 1068; these issues would be resolved if\nthe AGN is the primary source of gamma-rays. We discuss the implications of\nthese results and make predictions for the neutrino fluxes for both galaxies.\n