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

¹ Institut de Ciències de l’Espai (IEEC-CSIC), Campus UAB, Torre C5, 2a planta, 08193 Barcelona, Spain
e-mail: gpedalet@ieec.uab.es
² Institució Catalana de Recerca i Estudis Avançats (ICREA), 08010 Barcelona, Spain
³ Astroparticule et Cosmologie (APC), CNRS, Université Paris 7 Denis Diderot, Paris, France
⁴ Max-Planck-Institut für Kernphysik (MPIK), PO Box 103980, 69029 Heidelberg, Germany
⁵ IFAE, Edifici Cn., Campus UAB, 08193 Bellaterra, Spain
⁶ Now at : Max-Planck-Institut für Physik, 80805 München, Germany

Received: 17 October 2012
Accepted: 22 December 2012

Abstract

Aims. Molecular clouds act as primary targets for cosmic-ray interactions and are expected to shine in γ-rays as a by-product of these interactions. Indeed, several detected γ-ray sources both in HE and VHE γ-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 γ-ray signals. In this work we explore the capability of the forthcoming Cherenkov Telescope Array observatory (CTA) to provide such measurements.

Methods. 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.

Results. We present some of the most interesting cases for CTA regarding this science topic. The simulated γ-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.