TY - JOUR
T1 - High-energy emission from star-forming galaxies
AU - Persic, M.
AU - Rephaeli, Y.
PY - 2011
Y1 - 2011
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=84870426311&partnerID=8YFLogxK
U2 - 10.1393/ncc/i2011-10858-1
DO - 10.1393/ncc/i2011-10858-1
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AN - SCOPUS:84870426311
SN - 2037-4909
VL - 34
SP - 217
EP - 222
JO - Nuovo Cimento della Societa Italiana di Fisica C
JF - Nuovo Cimento della Societa Italiana di Fisica C
IS - 3
ER -