γ-ray Sources Within Our Galaxy And The Origin Of VHE Cosmic Rays

The origin of very high energy (VHE) cosmic rays(CRs) is one of the most difficult puzzles in the last century. Since its discovery in1912, we still have not found clear evidence on the main sites of CR acceleration. Thanks to the rapid development of the ground and space γ-ray instruments, the accumulation of high-energy data may help us gradually reveal the origin of CR. In this thesis, we developed some theoretical models for the multi-band data to explore this puzzle.In the first chapter, we review the current status of CR research and its relationship to the Galactic γ-ray sources.In the second chapter, the non-thermal radiation and particle acceleration process-es are shortly reviewed, along with several observations related to these theories. This review, which contains some useful order of magnitude estimations, is the basis of subsequent chapters.The third chapter is based on our own work, which begins with the possible sites of CR acceleration within our Galaxy:supernova remnants(SNRs) and pulsar wind nebulae(PWNe). After a brief introduction to the SNR evolution, we applied our spec-tral inversion method to the young SNR RX J1713.7-3946and show a favor of the leptonic origin of its γ-rays. For the γ-rays from old SNRs interacting with molecu-lar clouds, an accumulative diffusive model is developed in order to explain the GeV and TeV spectra of SNRs W28and G35.6-0.4. These fitting results naturally show strong evidence that SNRs do accelerate protons to relativistic energy and release them to the interstellar medium. We then improve the model by incorporating the finite volume of molecular clouds, demonstrate the model dependence on particle diffusion parameters and cloud size, and apply it to nine interacting SNRs. This unified model naturally explains their GeV spectral breaks and, in particular, the ’platforms’, together with available TeV data. PWNe are another possible sites which are able to accelerate CRs. Beginning with the continuous equation in energy space, we develop a leptonic time-dependent model and explain the observed evolution law of X-ray and γ-ray lu-minosity. Finally, we point out that the multi-band non-thermal emission from PWN G54.1+0.3cannot be explained by the pure leptonic model, and a hadronic component must be introduced, which supports CR acceleration in PWNe.The fourth chapter is the summary of our work during my graduate study, the un-solved problems in the field of CR, and the prospects of further exploration in the CRs study.