Cosmic infrared background excess from axion-like particles and implications for multi-messenger observations of blazars

The first measurement of the diffuse background spectrum at 0.8-1.7 $\mu \rm{m}$ from the CIBER experiment has revealed a significant excess of the cosmic infrared background (CIB) radiation compared to the theoretically expected spectrum. We revisit the hypothesis that decays of axionlike particle (ALP) can explain this excess, extending previous analyses to the case of a warm relic population. We show that such a scenario is not excluded by anisotropy measurements nor by stellar cooling arguments. Moreover, we find that the increased extragalactic background light (EBL) does not contradict observations of blazar spectra. Furthermore, the increased EBL attenuates the diffuse TeV gamma-ray flux and alleviates the tension between the detected neutrino and gamma ray fluxes.Comment: 11 pages, 5 figures. Several changes to match published versio

On the contribution of cosmic-ray interactions in the circumgalactic gas to the observed high-energy neutrino flux

Cosmic rays escaping the Milky-Way disk interact with circumgalactic gas which fills the virial volume of our Galaxy. These interactions should produce guaranteed fluxes of energetic diffuse neutrinos and photons observable at the Earth. This neutrino flux would be a plausible contribution to the spectrum measured by the IceCube neutrino observatory: the energy emitted in this way is weakly constrained from cascade gamma rays, since the cascades have no time to develop, but the arrival directions of the neutrinos do not point to the Galactic disk, in agreement with observations. However, previous studies reported very different estimates of the corresponding neutrino flux, so it was unclear if this contribution to the observed spectrum is essential. Here we readdress the calculation of this diffuse neutrino flux component under various assumptions about the cosmic-ray spectrum and propagation in the circumgalactic medium. We find that even with these variations, this contribution to the observed neutrino flux remains subleading provided multimessenger constraints are satisfied.Comment: 19 pages, 6 figures; v2: discussions extended; version accepted by JCA

GZK Photons in the Minimal Ultra High Energy Cosmic Rays Model

In a recently proposed model the cosmic rays spectrum at energies above 10^{18} eV can be fitted with a minimal number of unknown parameters assuming that the extragalactic cosmic rays are only protons with a power law source spectrum ~E^{-alpha} and alpha~2.6. Within this minimal model, after fitting the observed HiRes spectrum with four parameters (proton injection spectrum power law index and maximum energy, minimum distance to sources and evolution parameter) we compute the flux of ultra-high energy photons due to photon-pion production, the GZK photons, for several radio background models and average extragalactic magnetic fields with amplitude between 10^{-11} G and 10^{-9} G. We find the photon fraction to be between 10^{-4} and 10^{-3} in cosmic rays at energies above 10^{19} eV. These small fluxes could only be detected in future experiments like Auger North plus South and EUSO.Comment: 13 pages, 9 figure