Title:	Testing hadronic models of gamma ray production at the core of Cen A
Authors:	Joshi, Jagdish C. Gupta, Nayantara
Keywords:	Radio galaxies gamma-ray Neutrino muon cosmic rays
Issue Date:	15-Jan-2013
Publisher:	American Physical Society
Citation:	Physical Review D, 2013, Vol.87, p 023002
Abstract:	The Pierre Auger experiment has observed a few cosmic ray events above 55 EeV from the direction of the core of Cen A. These cosmic rays might have originated from the core of Cen A. High-energy gamma ray emission has been observed by HESS from the radio core and inner kpc jets of Cen A. We are testing whether pure hadronic interactions of protons or heavy nuclei with the matter in the core region or photodisintegration of heavy nuclei can explain the cosmic ray and high-energy gamma ray observations from the core of Cen A. The scenario of p-γ interactions followed by photopion decay has been tested earlier by Sahu et al. and found to be consistent with the observational results. In this paper, we have considered some other possibilities: (i) The primary cosmic rays at the core of Cen A are protons, and the high-energy gamma rays are produced in p-p interactions. (ii) The primary cosmic rays are Fe nuclei, and the high-energy gamma rays are produced in Fe-p interactions. (iii) The primary cosmic rays are Fe nuclei, and they are photodisintegrated at the core. The daughter nuclei deexcite, and high-energy gamma rays are produced. The high-energy gamma ray fluxes expected in each of these cases are compared with the flux observed by the HESS experiment to normalize the spectrum of the primary cosmic rays at the core. We have calculated the expected number of cosmic ray nucleon events to be between 55 and 150 EeV in each of these cases to verify the consistencies of the different scenarios with the observations by the Pierre Auger experiment. We find that if the primary cosmic rays are Fe nuclei, then their photodisintegration followed by the deexcitation of daughter nuclei may explain the observed high-energy particle emissions from the core of Cen A. The luminosity of the cosmic ray Fe nuclei required to explain the observational results of HESS and Pierre Auger is higher than the luminosity of the cosmic ray protons in the p-γ interaction model. The required cosmic ray luminosity depends on the density of the low-energy photons at the source, which photodisintegrate the Fe nuclei, and the size of the emitting region.
Description:	Open Access.
URI:	http://hdl.handle.net/2289/5546
ISSN:	1550-7998 1550-2368(Online)
Alternative Location:	http://adsabs.harvard.edu/abs/2013PhRvD..87b3002J http://arxiv.org/abs/1210.0479 http://dx.doi.org/10.1103/PhysRevD.87.023002
Copyright:	2013 American Physical Society
Appears in Collections:	Research Papers (A&A)

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