High-energy emission from star-forming galaxies

M. Persic, Y. Rephaeli

Research output: Contribution to journalArticlepeer-review

Abstract

Adopting the convection-diffusion model for energetic electron and proton propagation, and accounting for all the relevant hadronic and leptonic processes, the steady-state energy distributions of these particles in the starburst galaxies M 82 and NGC 253 can be determined with a detailed numerical treatment. The electron distribution is directly normalized by the measured synchrotron radio emission from the central starburst region; a commonly expected theoretical relation is then used to normalize the proton spectrum in this region, and a radial profile is assumed for the magnetic field. The resulting radiative yields of electrons and protons are calculated: the predicted > 100 MeV and > 100 GeV fluxes are in agreement with the corresponding quantities measured with the orbiting Fermi telescope and the ground-based VERITAS and HESS Cherenkov telescopes. The cosmic-ray energy densities in central regions of starburst galaxies, as inferred from the radio and γ-ray measurements of (respectively) non-thermal synchrotron and π -decay emission, are Up = O(100) eVcm-3, i.e. at least an order of magnitude larger than near the Galactic center and in other non-very-actively star-forming galaxies. These very different energy density levels reflect a similar disparity in the respective supernova rates in the two environments. A Lγ ∞ SFR1.4 relationship is then predicted, in agreement with preliminary observational evidence.

Original languageEnglish
Pages (from-to)217-222
Number of pages6
JournalNuovo Cimento della Societa Italiana di Fisica C
Volume34
Issue number3
DOIs
StatePublished - 2011

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