Cosmic ray transport and radiative processes in nuclei of starburst galaxies. (arXiv:1812.01996v1 [astro-ph.HE])

Cosmic ray transport and radiative processes in nuclei of starburst galaxies. (arXiv:1812.01996v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Peretti_E/0/1/0/all/0/1">Enrico Peretti</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Blasi_P/0/1/0/all/0/1">Pasquale Blasi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Aharonian_F/0/1/0/all/0/1">Felix Aharonian</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Morlino_G/0/1/0/all/0/1">Giovanni Morlino</a>

The high rate of star formation and supernova explosions of starburst
galaxies make them interesting sources of high energy radiation. Depending upon
the level of turbulence present in the their interstellar medium, the bulk of
cosmic rays produced inside starburst galaxies may lose most of their energy
before escaping, thereby making these sources behave as calorimeters, at least
up to some maximum energy. Contrary to previous studies, here we investigate in
detail the conditions under which cosmic ray confinement may be effective for
electrons and nuclei and we study the implications of cosmic ray confinement in
terms of multifrequency emission from starburst nuclei and production of high
energy neutrinos. The general predictions are then specialized to three cases
of active starbursts, namely M82, NGC253 and Arp220. Both primary and secondary
electrons, as well as electron-positron pairs produced by gamma ray absorption
inside starburst galaxies are taken into account. Electrons and positrons
produced as secondary products of hadronic interactions are found to be
responsible for most of the emission of leptonic origin. In particular,
synchrotron emission of very high energy secondary electrons produces an
extended emission of hard X-rays that represent a very interesting signature of
hadronic process in starburst galaxies, potentially accessible to current and
future observations in the X-ray band. A careful understanding of both the
production and absorption of gamma rays in starburst galaxies is instrumental
to the assessment of the role of these astrophysical sources as sources of high
energy astrophysical neutrinos.

The high rate of star formation and supernova explosions of starburst
galaxies make them interesting sources of high energy radiation. Depending upon
the level of turbulence present in the their interstellar medium, the bulk of
cosmic rays produced inside starburst galaxies may lose most of their energy
before escaping, thereby making these sources behave as calorimeters, at least
up to some maximum energy. Contrary to previous studies, here we investigate in
detail the conditions under which cosmic ray confinement may be effective for
electrons and nuclei and we study the implications of cosmic ray confinement in
terms of multifrequency emission from starburst nuclei and production of high
energy neutrinos. The general predictions are then specialized to three cases
of active starbursts, namely M82, NGC253 and Arp220. Both primary and secondary
electrons, as well as electron-positron pairs produced by gamma ray absorption
inside starburst galaxies are taken into account. Electrons and positrons
produced as secondary products of hadronic interactions are found to be
responsible for most of the emission of leptonic origin. In particular,
synchrotron emission of very high energy secondary electrons produces an
extended emission of hard X-rays that represent a very interesting signature of
hadronic process in starburst galaxies, potentially accessible to current and
future observations in the X-ray band. A careful understanding of both the
production and absorption of gamma rays in starburst galaxies is instrumental
to the assessment of the role of these astrophysical sources as sources of high
energy astrophysical neutrinos.

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