Shock-Cloud Interaction in RX J1713.7−3946: Evidence for Cosmic-Ray Acceleration in the Young VHE γ-ray Supernova Remnant (Springer Theses)

This book presents a study of the young supernova remnant RX J1713.7-3946 in order to reveal the origin of cosmic rays in our galaxy. The study focuses on the X-ray and gamma radiation from the cosmic ray electrons and protons in the supernova remnant as well as the emission from the surrounding interstellar gas measured by the NANTEN2 4-m radio telescope at Nagoya University. The gamma rays show a good spatial correspondence with the interstellar gas, which for the first time provides strong evidence of the acceleration of cosmic ray protons. Additionally, the author determines that an interaction between the supernova shockwaves and interstellar gas, referred to as “shock-cloud interaction,” promotes the efficient acceleration of cosmic ray electrons in the supernova remnant. The book reveals that the interstellar gas plays an essential role in producing the high-energy radiation and cosmic rays, offering vital new insights into the origin and behavior of galactic cosmic rays. Supervisor’s Foreword 6 Parts of this thesis have been published in the following journal articles: 8 Acknowledgements 9 Contents 11 1 Introduction 14 1.1 Background 14 1.2 Cosmic Rays 16 1.3 Cosmic Ray Acceleration in Supernova Remnants 18 1.3.1 Kinetic Energy Budget 18 1.3.2 Diffusive Shock Acceleration 19 1.4 Radiative Processes of High Energy Cosmic Rays 22 1.4.1 Synchrotron Radiation 23 1.4.2 Inverse Compton Scattering 25 1.4.3 π0-Decay Emission 25 1.5 Association Between SNRs and the Interstellar Gas 27 1.5.1 Overview of Previous Studies 27 1.5.2 Previous Studies of the Young SNR RX J1713.7-3946 30 1.6 Thesis Outline 35 References 35 2 Non-thermal X-Ray Enhancement Around Dense Gas Clumps 38 2.1 Datasets of CO, Hi, and X-Rays 39 2.1.1 CO 39 2.1.2 Hi 41 2.1.3 X-Rays 41 2.2 Analysis 43 2.2.1 Large-Scale CO, Hi, and X-Ray Distributions 43 2.2.2 Detailed Comparison with X-Ray Data 49 2.2.3 Sub-Millimeter Results; 12CO(J = 4--3) Distribution 60 2.2.4 12CO(J = 4--3) Broad Wings 61 2.3 Analysis of Detailed Molecular Properties 64 2.3.1 LVG Analysis 64 2.3.2 Density Distribution of Clump C 66 2.3.3 Physical Parameters of the Outflow 67 2.4 Discussion 68 2.5 Conclusions 71 References 72 3 Evidence for the Acceleration of Cosmic Ray Protons 75 3.1 Datasets of CO, Hi, and VHE γ-rays 76 3.1.1 CO 76 3.1.2 Hi 77 3.1.3 VHE γ-rays 77 3.2 Combined Analysis of the CO and Hi Data 77 3.2.1 Distribution of CO and Hi 77 3.2.2 Molecular Protons 79 3.2.3 Atomic Protons 80 3.2.4 Total ISM Protons 85 3.2.5 γ-rays and the ISM Protons 86 3.3 Discussion 90 3.3.1 The Evacuated Cavity by the Stellar Wind 90 3.3.2 γ-ray Emission Mechanism 92 3.4 Conclusions 94 References 95 4 Evidence for Efficient Acceleration of Cosmic Rays 97 4.1 Observations and Data Reductions 97 4.1.1 X-Rays 97 4.1.2 CO and Hi 100 4.2 Results 102 4.2.1 Typical X-Ray Spectra 102 4.2.2 Spatial and Spectral Characterization of the X-Rays 102 4.2.3 Comparison with the ISM: The X-Ray Flux, Photon Index, and ISM 104 4.3 Discussion 107 4.3.1 Spatial Variation of the Absorbing Column Density 107 4.3.2 Relationship Among the X-Ray Flux, Photon Index, and X-Ray Absorption/ ISM 109 4.4 Conclusions 114 References 115 5 Summary and Future Prospects 116 5.1 Summary of the Thesis 116 5.2 Future Prospects 119 5.2.1 Further Expansion Our Studies into Analysis of Other SNRs 119 5.2.2 Resolving the Small-Scale Structure of SNR RX J1713.7-3946 122 5.2.3 More Detailed Analyses from a Viewpoint of Numerical Simulations 122 5.2.4 Shock Speed Measurement Toward Southeastern Rim of RX J1713.7-3946 122 5.2.5 Search for Thermal X-Rays in Synchrotron Dominant SNRs 123 References 123 Appendix A Velocity Channel Distributions in RX J1713.7-3946 125 A.1 CO and Non-thermal X-Rays (J2000 Coordinate) 125 A.2 CO, Hi and VHE γ-Rays (Galactic Coordinate) 125 Appendix B Expanding Motion of the Dark Hi SE Cloud 132 Appendix C Analysis of the Hi Emission; The Optically Thin Case 136 Appendix D The Background Level of X-Rays 139 Appendix E X-Ray Absorption by the ISM Affects the X-Ray Images 140 Front Matter....Pages i-xiii Introduction....Pages 1-24 Non-thermal X-Ray Enhancement Around Dense Gas Clumps....Pages 25-61 Evidence for the Acceleration of Cosmic Ray Protons....Pages 63-84 Evidence for Efficient Acceleration of Cosmic Rays....Pages 85-103 Summary and Future Prospects....Pages 105-113 Back Matter....Pages 115-134