Diffuse Galactic Gamma Rays at Intermediate and High Latitudes, Constraints on ISM Properties

TL;DR

This study uses Fermi gamma-ray data and the DRAGON code to analyze cosmic ray propagation and interstellar medium properties, providing new constraints on propagation models at high latitudes.

Contribution

It introduces a comprehensive analysis of gamma-ray emissivity using various propagation models and critically evaluates gas distribution models in the Galaxy.

Findings

Certain propagation models fit the gamma-ray data better.

Constraints on diffusion and re-acceleration parameters are established.

Gas distribution models significantly impact gamma-ray emissivity predictions.

Abstract

The spectral data on the diffuse Galactic gamma-rays, at medium and high latitudes (|b| > 10) and energies of 1-100 GeV, recently published by the Fermi Collaboration are used to produce a novel study on the gamma-ray emissivity in the Galaxy. We focus on analyzing the properties of propagation of cosmic rays (CRs), using the publicly available DRAGON code. We critically address some of the models for the interstellar HI and H2 gas distributions commonly used in the literature, as well as test a variety of propagation models. Each model assumes a distinct global profile for the diffusion and the re-acceleration of CRs. Fitting propagation parameters to well measured local CRs such as, the B/C ratio, protons, antiprotons and electron, positron fluxes, we evaluate the gamma-ray spectra at medium and high latitudes in order to place further constraints on these propagation models.