Cherenkov Telescope Array Observatory sensitivity to heavy Galactic Cosmic Rays and the shape of particle spectrum

TL;DR

This study uses simulations to demonstrate that the Cherenkov Telescope Array Observatory can better identify the spectral shape of gamma-ray emissions from supernova remnants, helping to clarify the origin of Galactic Cosmic Rays and their acceleration mechanisms.

Contribution

The paper presents new simulation results showing CTAO's enhanced sensitivity to heavy cosmic rays and spectral cut-off sharpness, aiding in understanding cosmic-ray sources and acceleration processes.

Findings

CTAO can distinguish heavy CRs from protons in gamma-ray spectra.

Sensitivity improvements allow constraining particle spectrum cut-off sharpness.

Results support CTAO's role in elucidating cosmic-ray acceleration scenarios.

Abstract

The origin of Galactic Cosmic Rays (GCRs) and the potential role of Supernova Remnants (SNRs) as cosmic-ray (CR) accelerators remain subjects of ongoing debate. To shed more light on this topic, we have studied the spectral shape of two SNRs, RX J1713.7-3946 and HAWC J2227+610, performing simulations for the Cherenkov Telescope Array Observatory (CTAO). The previous multi-wavelength (MWL) analysis on these two sources showed an important hadronic contribution at high energies. The interaction of the GCRs accelerated by the SNRs with the medium around the accelerator leads to a process of pion decay (PD) that produces gamma-rays ($\gamma$-rays). These emissions, detectable by CTAO, offer an indirect means of pinpointing the CR source. Two scenarios have been considered: the contribution of heavy CRs and different cut-off sharpnesses ($\beta$) of the particle spectra. The simulations were performed by using different CR composition distributions (protons, CNO, Fe) and different sharpness values ranging from $\beta$=0.5 to $\beta$=1.5. The results show that, in the cases studied here, CTAO will increase the sensitivity to the spectral shape of $\gamma$-rays. This allows us to distinguish protons from heavy CRs and obtain information on $\beta$ values and therefore on different acceleration scenarios.