On the potential of the Cherenkov Telescope Array for the study of cosmic-ray diffusion in molecular clouds

TL;DR

This paper assesses the Cherenkov Telescope Array's potential to study cosmic-ray diffusion in molecular clouds by simulating gamma-ray emissions and evaluating CTA's ability to constrain cosmic-ray and source properties.

Contribution

It explores how CTA observations can be used to measure cosmic-ray diffusion and source characteristics in molecular clouds, considering various astrophysical parameters.

Findings

CTA can potentially constrain cosmic-ray diffusion coefficients.

Gamma-ray fluxes are highly sensitive to source and environmental parameters.

Certain scenarios allow CTA to distinguish between different cosmic-ray propagation modes.

Abstract

Molecular clouds act as primary targets for cosmic-ray interactions and are expected to shine in gamma-rays as a by-product of these interactions. Indeed several detected gamma-ray sources both in HE and VHE gamma-rays (HE: 100 MeV < E < 100 GeV; VHE: E > 100 GeV) have been directly or indirectly associated with molecular clouds. Information on the local diffusion coefficient and the cosmic-ray population can be inferred from the observed gamma-ray signals. In this work we explore the capability of the forthcoming Cherenkov Telescope Array Observatory (CTA) to provide such measurements. We investigate the expected emission from clouds hosting an accelerator, surveying the parameter space for different modes of acceleration, age of the source, cloud density profile, and cosmic-ray diffusion coefficient. We present some of the most interesting cases for CTA regarding this science topic. The simulated gamma-ray fluxes depend strongly on the input parameters. In several cases, we find that it will be possible to constrain both the properties of the accelerator and the propagation mode of cosmic rays in the cloud from CTA data alone.