I Introduction to the Interstellar Medium（我介绍了星际介质）.pdf

I Introduction to the Interstellar Medium “The Interstellar Medium is anything not in stars” Donald Osterbrock [1984 Jan 13 – author’s UCSC course notes]. Astronomy 871 is a survey of the physics of the Interstellar Medium (henceforth ISM) of the Milky Way Galaxy. The emphasis will be on physical processes that prevail in each of the distinct phases of interstellar gas. In the end, you should have a thorough grounding in the basic physical principles necessary to pursue research in the field. As such, we will spend little time on current research results or questions, except insofar as they will illustrate the physics of interest to us here. This is not to say that the current research is unimportant, but rather that we are concerned with bringing you up to speed on the basic conceptual tools of that research. The course is divided into the following parts: 1. Introduction to the ISM, a basic physical description of the ISM, and an overview of global ISM models (the multi-phase ISM). 2. Physics of neutral Hydrogen (HI) regions, concentrating on UV and visible absorption lines and the HI 21-cm hyperfine structure line. 3. Physics of ionized Hydrogen (HII) regions, with an emphasis on the physics of ionization and thermal equilibrium, recombination lines, nebular continuum, and spectral diagnostics of density, temperature, and abundances 4. Interstellar Dust, with an emphasis on interstellar extinction, spectral properties of dusty regions, the thermal properties of grains, grain formation and destruction, and depletion of gas- phase elements onto grains. 5. Physics of Molecular Clouds (H2), including mm and radio rotational line formation (esp. CO), diagnostics of cloud kinematics and structure, molecular hydrogen physic