CTA and cosmic-ray diffusion in molecular clouds

TL;DR

This paper explores how the upcoming CTA observatory can measure gamma-ray emissions from molecular clouds to understand cosmic-ray diffusion and acceleration processes within them.

Contribution

It assesses CTA's potential to constrain cosmic-ray properties and acceleration mechanisms in molecular clouds through simulated gamma-ray observations.

Findings

CTA can potentially constrain cosmic-ray diffusion coefficients.

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

Certain scenarios allow detailed characterization of cosmic-ray propagation.

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 local cosmic-ray population can be deduced from the observed gamma-ray signals. In this work we concentrate on the capability of the forthcoming Cherenkov Telescope Array Observatory (CTA) to provide such measurements. We investigate the expected emission from clouds hosting an accelerator, exploring 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 some cases, from CTA data it will be possible to constrain both the properties of the accelerator and the propagation mode of cosmic rays in the cloud.