Correlation of γ-ray and high-energy cosmic ray fluxes from the giant lobes of Centaurus a

Abstract

The spectral energy distribution of giant lobes shows one main peak detected by the Wilkinson Microwave Anisotropy Probe at the low energy of 10-5 eV and a faint γ-ray flux imaged by the Fermi Large Area Telescope at an energy of ≥100 MeV. On the other hand, the Pierre Auger Observatory associated some ultra-high-energy cosmic rays with the direction of Centaurus A and IceCube reported 28 neutrino-induced events in a TeV-PeV energy range, although none of them related with this direction. In this work, we describe the spectra for each of the lobes, the main peak with synchrotron radiation, and the high-energy emission with p-p interactions. After obtaining a good description of the main peak, we deduce the magnetic fields, electron densities, and the age of the lobes. Successfully describing the γ-ray emission by p-p interactions and considering thermal particles in the lobes with density in the range 10-10-10-4 cm-3 as targets, we calculate the number of ultra-high-energy cosmic rays. Although the γ-spectrum is well described with any density in the range, only when 10-4 cm-3 is considered are the expected number of events very similar to that observed by the Pierre Auger Observatory, otherwise we obtain an excessive luminosity. In addition, correlating the γ-ray and neutrino fluxes through p-p interactions, we calculate the number of high-energy neutrinos expected in IceCube. Our analysis indicates that neutrinos above 1 TeV cannot be produced in the lobes of Centaurus A, which is consistent with the results recently published by the IceCube Collaboration. © 2014. The American Astronomical Society. All rights reserved..