Diffusion of cosmic rays and the gamma-ray large area telescope: Phenomenology at the 1-100 GeV regime

This paper analyzes astrophysical scenarios that may be detected at the upper end of the energy range of the Gamma-Ray Large Area Space Telescope (GLAST), as a result of cosmic-ray (CR) diffusion in the interstellar medium (ISM). Hadronic processes are considered the source of γ-ray photons from localized molecular enhancements nearby accelerators. Two particular cases are presented: (1) the possibility of detecting spectral energy distributions (SEDs) with maxima above 1 GeV, which may be constrained by detection or nondetection at very high energies (VHEs) with observations by ground-based Cerenkov telescopes, and (2) the possibility of detecting V-shaped, inverted spectra, due to confusion of a nearby (to the line of sight) arrangement of accelerator/target scenarios with different characteristic properties. We show that finding these signatures (in particular, a peak at the 1-100 GeV energy region) indicates the underlying mechanism producing the γ-rays that is realized by nature, which accelerator (age and relative position to the target cloud) and under which diffusion properties CRs propagate. © 2008. The American Astronomical Society. All rights reserved.