Neutrinos from Cosmic Ray Accelerators in the Cygnus Region of the Galaxy∗

While supernova remnants have been identified as the most likely sources of the galactic cosmic rays, no conclusive observational evidence for this association exists. We show here that IceCube has the possibility of producing incontrovertible evidence by detecting neutrinos produced by the cosmic ray beam interacting with the hydrogen in the vicinity of the supernova shock expanding into the interstellar medium. We show that the observational information on gamma ray fluxes from the Cygnus region, although limited, is sufficient to pinpoint the expected event rate of the neutrinos associated with a single source of 0.5 Crab at the TeV level to within a factor of two, between 2 and 3.8 neutrinos per year. Finally, we note that recent gamma-ray observations reveal the presence of at least three and possibly up to eight such sources, raising the possibility of seeing more than 10 neutrinos per year from these sources alone. 1. Cosmic Neutrinos Associated with Galactic Cosmic Rays Cosmic accelerators produce particles with energies in excess of 10TeV; we do not know where or how. The flux of cosmic rays observed at Earth follows a broken power law. The two power laws are separated by a feature dubbed the “knee”. Circumstantial evidence exists that cosmic rays, up to perhaps EeV energy, originate in galactic supernova remnants. Any association with our Galaxy disappears in the vicinity of a second feature in the spectrum referred to as the “ankle”. Above the ankle, the gyroradius of a proton in the galactic magnetic field exceeds the size of the Galaxy and it is generally assumed that we are witnessing the onset of an extragalactic component in the spectrum that extends to energies beyond 100EeV. While the enigmatic nature of the highest energy cosmic rays has been widely advertised, it is also a fact that the origin of the galactic cosmic rays has not been established. We will show here that the positive identification of supernova remnants as the cosmic ray accelerators is possible with the kilometer-scale neutrino observatories now in the planning or construction phase. Simple energetics point at the supernova origin of the galactic cosmic rays. By integrating the observed flux we can obtain the energy density ρE of cosmic rays in the galaxy from the relation that flux = velocity× density, or