High-energy emission from star-forming galaxies

Persic, M. and Rephaeli, Y. (2011) High-energy emission from star-forming galaxies. Il nuovo cimento C, 34 (3). pp. 217-222. ISSN 1826-9885

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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 M82 and NGC253 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 π0-decay emission, are Up = O(100) eV cm−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.

Item Type: Article
Uncontrolled Keywords: γ-ray ; Starburst galaxies and infrared excess galaxies ; Spiral galaxies (M 31 and M33) ; Magellanic Clouds and other irregular galaxies
Subjects: 500 Scienze naturali e Matematica > 530 Fisica
Depositing User: Marina Spanti
Date Deposited: 06 Apr 2020 18:41
Last Modified: 06 Apr 2020 18:41
URI: http://eprints.bice.rm.cnr.it/id/eprint/17271

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