Diffusion of cosmic-rays and the Gamma-ray Large Area Telescope: Phenomenology at the 1-100 GeV regime

TL;DR

This paper explores how cosmic-ray diffusion in the interstellar medium influences gamma-ray emissions detectable by the GLAST telescope, focusing on spectral features that reveal underlying astrophysical acceleration and propagation mechanisms.

Contribution

It introduces models predicting gamma-ray spectral signatures from cosmic-ray interactions, aiding interpretation of observations in the 1-100 GeV energy range.

Findings

Detection of spectral peaks above 1 GeV constrains cosmic-ray sources.

V-shaped spectra indicate complex source-target configurations.

Spectral features help identify cosmic-ray acceleration and diffusion properties.

Abstract

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 as the source of $\gamma$-ray photons from localized molecular enhancements nearby accelerators. Two particular cases are presented: a) the possibility of detecting spectral energy distributions (SEDs) with maxima above 1 GeV, which may be constrained by detection or non-detection at very-high energies (VHE) with observations by ground-based Cerenkov telescopes, and b) 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 the finding of these signatures (in particular, a peak at the 1--100 GeV energy region) is indicative for an identification of the underlying mechanism producing the $\gamma$-rays that is realized by nature: which accelerator (age and relative position to the target cloud) and under which diffusion properties CR propagate.