The Transport And Interactions Of Cosmic Rays In Interstellar And Circumgalactic Medium

Cosmic rays are extraterrestrial particles with energies from Me V to above 100 Ee V.After escaping from their acceleration sites,cosmic rays propagate in the space,experiencing advection by the wind,diffusion by the magnetic field and interaction with the medium.The direct measurement of cosmic ray propagation is complicated,the observation of gamma-rays,which are neutral particles with small cross section produced by interactions of cosmic rays with interstellar medium(ISM)or circumgalactic mmedium(CGM)and radiation fields,is a useful probe of cosmic ray propagation and interactions.In this thesis,we study the propagation of cosmic rays through interpreting the gamma-ray observations.In the first chapter,we briefly introduce the related background knowledge,including the theory of the propagation and interactions of cosmic rays in the medium,and the production and observations of gamma-ray.In chapter 2,we use a noval method to measure the baryon mass in CGM,by comparing the theoretical gamma-ray emission produced by the interactions between cosmic rays and gas to the gamma-ray observations of the extended halo of the M31 galaxy.In chapter 3,we calculate the gamma-ray production efficiency in star-forming galaxies and explain the scaling relationship between the gamma-ray luminosity in Ge V energies and the total infrared luminosity of star-forming galaxies.In chapter 4,we investigate how the proper motion of a pulsar influences the morphology of its gamma-ray halo and discuss the influence of different parameters,this is helpful to constrain the origins of the observed extended sources around the pulsar at very high energies.In the last chapter,we give a brief discussion and summary of the thesis.