Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

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

Lin Nie, Yi-Qing Guo, Si-Ming Liu

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.

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

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.
Paper Structure (7 sections, 12 equations, 6 figures, 2 tables)

This paper contains 7 sections, 12 equations, 6 figures, 2 tables.

Table of Contents

  1. Introduction
  2. MODEL & METHODOLOGY
  3. Calculation of Background "Sea" CR protons
  4. Reacceleration and Adiabatic Compression of Background "Sea" CRs
  5. Component of the Thermal Injected Particles
  6. Results and Discussion
  7. Conclusion and Summary

Figures (6)

  • Figure 1: A comparison of the B/C ratio calculated using the CR SDP model with observational data from AMS-02 2017PhRvL.119y1101A, PAMELA 2014ApJ...791...93A, and DAMPE 2022SciBu..67.2162D. The pink and green shaded areas represent the fluxes from sources within ($\rm r < 1 ~kpc$) and beyond ($\rm r > 1 ~ kpc$) 1 kpc, respectively. In this study, the solar modulation potential is consistently assumed to be 550 MeV.
  • Figure 2: The CR proton spectrum is calculated using the CR SDP model and compared with observational data from AMS-02 2015PhRvL.114q1103A and DAMPE 2019SciA....5.3793A. The pink and green shaded areas represent the fluxes from sources within ($\rm r < 1~kpc$) and beyond ($\rm r > 1 ~kpc$) 1 kpc, respectively.
  • Figure 3: The gamma ray spectra predicted by model compared with the observational data for SNRs CasA (left). The observational data are taken from the LHAASO and Fermi-LAT 2025ApJ...982L..33C. The right panel show that the fitting 1-dimensional probability distributions (diagonal) and 2-dimensional credible regions of the model parameters.
  • Figure 4: The same as left panel of figure \ref{['fig3']} but for the Tycho. The observational data are taken from the Fermi-LAT 2022ApJS..260...53A and SHALON 2018AdSpR..62.2845S.
  • Figure 5: The same as left panel of figure \ref{['fig3']} but for the W44 (left panel) and IC443 (right panel). The observational data are taken from the Fermi-LAT 2013Sci...339..807A, MAGIC2007ApJ...664L..87A and LHAASO 2025arXiv251026112C. Here, C0 and C1 refer to the regions around a pointlike source, with angular extensions of approximately $0.27\degree$ and $0.67\degree$, respectively 2025arXiv251026112C.
  • ...and 1 more figures