Ay102: Interstellar Medium

The class meets Monday, Wednesday & Friday form 1-2pm in Cahill room 219. The textbookf for the course is Physics of the Interstellar and Intergalactic Medium by Bruce Draine. I would recommend that you buy a copy of Draine's book. Below "Chapter" refers to appropriate chapter in Draine's book. I will make use of a variety of sources for pedagogy. My internal notes will be linked to the class website.
Other Useful Books:
Radiative Processes in Astrophysics by George B. Rybicki & Alan P. Lightman
Quantum Mechanics for Engineers by Leon van Dommelen
Electromagnetic Processes by Robert J. Gould

The Physics of Interstellar Dust by Endkri Krugel
Astrophysics of gaseous nebulae and active galactic nuclei by Donald E. Osterbrock, Gary J. Ferland

I have provided links to some notes from courses taught elsewhere.
Michigan QM are notes of first level QM course taught at U. Michigan.

HOMEWORK POLICY: You are free to discuss amongst yourselves. In fact, much of learning is peer-to-peer. Brain storming is good. However, true understanding comes from within and so there is a delicate balance between communal problem solving and deep contemplation. The latter will stand you in good stead. I suggest the following approach: do your best to solve the homework. Sometimes you simply cannot make a headway. Those problems are grist to group discussions. Please include the sole undergrad in your discussions. What you submit must your own work (typed, written, programmed, drawn).

FINAL & MID-TERM EXAMS: These are oral exams (CLOSED BOOK). A master list of questions (approximately 25 for Mid-Term and 50 for Final) will be provided several weeks in advance of the exam. You are encouraged to discuss the solutions to these questions amongst yourselves. During the exam week, each of you will sign up for a slot. You arrive 1 hour before the assigned time and pick up a Chinese cookie from a jar. Each cookie has five lucky numbers (between 1 and 25/50). You then wend off to a quiet corner and mull through the questions. You can use a blank notebook to write down and work out your anwers (but no access to any other material, on- or off-line). [All relevant constants will be provided]. You then to the examination room and explain the solutions to the five assigned questions Typicall, the oral exam lasts 45 minutes. At the end of the exam period you will be provided with a letter summarizing your performance in the class.

GRADING FRAMEWORK: The final grade is a weighted sum with weith of 1/2 for homework, 1/4 each for mid-term and final.


  1. Introducing the ISM [4 January 2023]
    Introduction to ISM

  2. The Bohr Atom; Schrodinger solution [6 January 2023]
    Chapter 7 of Michigan QM  |  Bohr Hydrogen (SRK)  | 

  3. Corrections (Spin-orbit, relativistic); Dirac Solution [9 January 2023]
    SRK Notes   |   Kastberg's lecture notes
    Homework 1 (due 17 January);

  4. Helium [11 January 2023]
    Chapter 8 of Michigan QM  |  Helium (SRK)
    Additional Material: Hylleraas solution

  5. Allkali Elements, Multi-electrons [13 January 2023]
    Alkali spectra  |  SCF, spin orbitals  |  Chapter 9 of Michigan QM  | 

  6. L-S Coupling, Hunds rules, Selection Rules [18 January 2023]
    L-S coupling  |  Terms, Hund's rules
    Homework 2 due COB, Jan 24.

  7. Rate Coefficients [20 January 2023]
    Chapter 6
    Pre-requisites: A & B Coefficients  |  Maxwell-Boltzmann distribution

  8. Cross-sections [23 January 2023]
    Chapter 2
    SRK Notes

  9. Critical Density, Equilibration [25 January 2023]
    Nebulium  |  Dielectronic Recombination
    Please read Dispersion Measure (Kulkarni) ahead of next lecture.
    Homework 3 due February 2, 2023.

  10. Atomic Phases of the ISM: The Warm Ionized Medium [27 January 2023]
    Warm Ionized Medium
    Supplementary Reading: History of Radio Astronomy  |  SRK paper on mid-IR fine structure lines

  11. HII Regions (Stromgren model) [1 February 2023]
    Chapter 15 HII Regions

  12. Thermal Balance of HII regions [3 February 2023]
    Chapter 27
    Heating & Cooling

  13. HII regions: Dynamics [6 February 2023]
    Chapter 37
    Dynamics

  14. HII regions: Dynamics (continued) [8 February 2023]

  15. Cosmic Ray: Heating & Ionization [10 February 2023]
    Chapter 13.5 & Chapter 40
    Cosmic Rays, LISM

  16. Shocks & Jump Condtions [13 February 2023]
    Chapter 36
    Presentation  |  Jump Conditions

  17. Supernovae [15 Feburary 2023]
    Chapter 29
    Notes

  18. Hot Ionized Medium [17 February 2023]
    Chapters 14.9, 34.1 and 34.2  |  HIM Presentation

  19. Hyperfine lines , Radiative Transfer [22 February 2023]
    Chapter 4.6, 17.3, Hyperfine Line   |   Spin Flip  |  Chapter 7, Notes

  20. Warm & Cold Neutral Medium [24 February 2023]
    Chapter 8  |  Notes

  21. Global ISM Model [27 February 2023]
    Chapter 30. Please read the Supplement to see two-phase model at work.
    presentation  |  Supplement
    The additional material required for the HW4 homework can be found here

  22. Molecules [1 March 2023]
    Chapter 32  |  presentation

  23. Molecules (contd) [3 March 2023]

  24. Dust-1 [6 March 2023]

  25. Dust-2 [8 March 2023]

  26. Dust-3 [10 March 2023]

  27. FINAL EXAM (17 March 2023)
    Master Question List