Galactic sources of high energy neutrinos

Abstract

The undisputed galactic origin of cosmic rays at energies below the so-called knee implies an existence of a nonthemal population of galactic objects which effectively accelerate protons and nuclei to TeV-PeV energies. The distinct signatures of these cosmic PeVatrons are high energy neutrinos and γ -rays produced through hadronic interactions. While γ -rays can be produced also by directly accelerated electrons, high energy neutrinos provide the most straightforward and unambiguous information about the nucleonic component of accelerated particles. The planned km 3 -volume class high energy neutrino detectors are expected to be sensitive enough to provide the first astrophysically meaningful probes of potential VHE neutrino sources. This optimistic prediction is based on the recent discovery of high energy γ -ray sources with hard energy spectra extending to 10 TeV and beyond. Amongst the best-bet candidates are two young shell-type supernova remnants – RXJ 1713.7-4946 and RXJ 0852.0-4622, and perhaps also two prominent plerions – the Crab Nebula and Vela X. Because of strong absorption of TeV γ -rays, one may expect detectable neutrino fluxes also from (somewhat fainter) compact TeV γ -ray emitters like the binary systems LS 5039 and LS I+61 303, and, hopefully, also from hypothetical “hidden” or “orphan” neutrino sources.