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| AST 393F |
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Purpose
To give students an overall familiarity and understanding of the basic physics, observations, and unsolved
problems in this field, and how they relate to other fields in astronomy. Also: using the ISM as an example
of the problems involved in a reductionist approach to understanding of a complex system.
Organization of Topics
Roughly 1.5-2 weeks on each; notice that because of the large amount of material, we may have to skip
some topics, or I may have to skip them in lecture (although possibly still assign readings).
I. Overview of observations and components of the ISM
S1, DW1, 2; Hartmann ch.1, pp.1-15; Duley & Williams ch.1, pp. 3-21.
Lecture will be comprehensive but qualitative overview of observations, with preview of theoretical issues.
II. Microscopic equilibrium and nonequilibrium physical processes
Kinds of equilibrium, radiative processes, excitation and level populations, diagnostics.
DW 1, pp. 8-26, easy summary of line and continuum processes.
S 2, pp. 18-31 on elastic collisions and kinetic equilibrium.
S 3 pp.32-68: radiative transfer, emission lines (HI 21cm, recombination, masers), absorption lines
(21 cm, H2, optic al lines), continuum emission and absorption by electrons.
S4 pp. 70-102: rate equations, detailed balance, collision rates, 2 and 3 level atom, optical emission lines,
molecular rotational lines, recombination lines, H2 levels.
III. Grains—optical properties, absorption features (2175, optical bands, IR bands) and
continuum emission; grain temperature; charge and photoelectric emission; polarization and alignment
(may have to skip); formation and destruction.
DW pp. 44-63.
S 7 (optical & observed properties), 8 (polarization and alignment; may skip); 9 (physical properties).
One or two modern review articles.
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