Cosmic rays, neutrinos and GeV-TeV gamma rays from Starburst Galaxy NGC 4945. (arXiv:2011.01847v3 [astro-ph.HE] UPDATED)

Cosmic rays, neutrinos and GeV-TeV gamma rays from Starburst Galaxy NGC 4945. (arXiv:2011.01847v3 [astro-ph.HE] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Aguilar_Ruiz_E/0/1/0/all/0/1">E. Aguilar-Ruiz</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Fraija_N/0/1/0/all/0/1">N. Fraija</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Joshi_J/0/1/0/all/0/1">Jagdish C. Joshi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Galvan_Gamez_A/0/1/0/all/0/1">A. Galvan-Gamez</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Diego_J/0/1/0/all/0/1">J.A. de Diego</a>

The detection of high-energy astrophysical neutrinos and ultra-high-energy
cosmic rays (UHECRs) provides a new way to explore cosmic rays’ sources. One of
the highest energy neutrino events detected by IceCube, tagged as IC35, is
close to the UHECR anisotropy region detected by Pierre Auger Observatory. The
nearby starburst galaxy (SBG), NGC 4945, is close to this anisotropic region
and inside the mean angular error of the IC35 event. Considering the hypernovae
contribution located in the SB region of NGC 4945, which can accelerate protons
up to $sim 10^{17} , rm eV$ and inject them into the interstellar medium, we
investigate the origin of this event around this starburst galaxy. We show that
the interaction of these protons with the SB region’s gas density could explain
Fermi-LAT gamma-ray and radio observations if the magnetic field’s strength in
the SB region is the order of $sim rm mG$. Our estimated PeV neutrino events,
in ten years, for this source is approximately 0.01 ($4times10^{-4}$) if a
proton spectral index of 2.4 (2.7) is considered, which would demonstrate that
IC35 is not produced in the central region of this SBG. Additionally, we
consider the superwind region of NGC 4945 and evidence that cosmic-ray protons
cannot be accelerated in it up to UHEs. Finally, we perform a UHECR statistical
analysis around NGC 4945, and show a possible contribution from this galaxy but
with alternatives acceleration sites.

The detection of high-energy astrophysical neutrinos and ultra-high-energy
cosmic rays (UHECRs) provides a new way to explore cosmic rays’ sources. One of
the highest energy neutrino events detected by IceCube, tagged as IC35, is
close to the UHECR anisotropy region detected by Pierre Auger Observatory. The
nearby starburst galaxy (SBG), NGC 4945, is close to this anisotropic region
and inside the mean angular error of the IC35 event. Considering the hypernovae
contribution located in the SB region of NGC 4945, which can accelerate protons
up to $sim 10^{17} , rm eV$ and inject them into the interstellar medium, we
investigate the origin of this event around this starburst galaxy. We show that
the interaction of these protons with the SB region’s gas density could explain
Fermi-LAT gamma-ray and radio observations if the magnetic field’s strength in
the SB region is the order of $sim rm mG$. Our estimated PeV neutrino events,
in ten years, for this source is approximately 0.01 ($4times10^{-4}$) if a
proton spectral index of 2.4 (2.7) is considered, which would demonstrate that
IC35 is not produced in the central region of this SBG. Additionally, we
consider the superwind region of NGC 4945 and evidence that cosmic-ray protons
cannot be accelerated in it up to UHEs. Finally, we perform a UHECR statistical
analysis around NGC 4945, and show a possible contribution from this galaxy but
with alternatives acceleration sites.

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