Two-component $\gamma$-Ray Structure from the CR Sources Within Dense Clouds

TL;DR

This paper proposes a two-component model explaining the double power-law gamma-ray spectra from cosmic ray sources, linking it to re-acceleration processes within dense clouds, and successfully reproduces observational data.

Contribution

It introduces a unified two-component model that accounts for the double power-law features in gamma-ray spectra and cosmic ray energy spectra from sources within dense clouds.

Findings

Model reproduces gamma-ray observations of multiple sources.

Supports double power-law as a common feature of Galactic CR sources.

Provides a new theoretical framework for CR origin and propagation.

Abstract

Recent observations have revealed that several cosmic ray (CR) sources themselves exhibit pronounced double power-law features in their radiation spectra. Combined with the phenomenon of two-component structure in the observed CR energy spectrum supported by multi-messenger data, this raises a fundamental question: can the two-component structure of the cosmic ray energy spectrum and the double power-law feature of the gamma-ray radiation energy spectrum from supernova remnants be understood within a unified picture? In this study, we propose a two-component model that incorporates the re-acceleration of background ``sea" CR particles by astrophysical sources to systematically explain the formation of double power-law spectra within those sources. Our model successfully reproduces the gamma-ray observations of multiple CR sources. The results support that double power-law structures may be a generic feature of Galactic CR sources within crushed clouds. This work offers a new theoretical perspective on the origin and propagation of cosmic rays, and its predictions may be further tested with future observations of a larger sample of CR sources.