ASTR670: The Interstellar Medium and Gas Dynamics
Spring 2019 - Course Information and Outline

Class schedule at

Materials at

 Class Meetings: ATL 0201, TuTh 12:30-1:45
Instructor: Alberto Bolatto
bolatto at, 301-405-1521, 1158 PSC  

Class Purpose

The interstellar medium is an extremely rarefied gas, for the most part a vacuum harder than any vacuum that can be obtained in a lab at the surface of the Earth. Yet it pervades the galaxy, and by mass it constitutes about a third of its baryons. It is an extremely dynamical multi-phase system fundamental to most processes that shape galaxies, such as star formation and black hole accretion. From the observational standpoint, it provides a large fraction of the spectroscopic and continuum information that we gather from any galaxy. This complex system, constituted by several phases with temperatures that range from several millions to tens of degrees Kelvin that coexist in dynamical equilibrium, has equally complex physics that we will cover in this course. The first half of the course discusses the individual phases, associated physics, and relevant diagnostics, while the second half focuses on the formal hydro- and magnetohydrodynamics of gases, including linear perturbation theory and shocks.


My expectation is that the students will conduct themselves as graduate students. This means putting electronic distractions to the side during the lectures, following the lecture material, following and reading references after lectures, and in general demonstrating curiosity. Assignments are individual, and should be completed by students independently. That does not mean that students should not be talking to each other about what they are doing (on the contrary, your objective should be to learn!), but it means that each one should arrive at the solutions through their own thought process and understanding (otherwise you are not learning!). I expect students will be curious enough to go above and beyond what I ask in the homeworks, rather than just following my script. Instead of worrying about the grade, worry about exploring and learning and the grade will come with that!

Class Meetings

The class meets in room 0201 of the Atlantic Building from on Tuesdays and Thursdays 12:30-1:45 pm (12:30­-13:45).   Because of some travel commitments, a few individual classes (marked with * in the calendar) will have to be scheduled to other mutually agreeable times.  Classes will consist primarily of intensive lectures and, I hope, equally intensive questions and discussions as we move through the course material.

Office Hours

Questions about lecture and problem sets or other topics are strongly encouraged.  Given everyone's varied schedules, we will do this by appointment or by random encounter.  Please come ask questions early as they emerge.  The hour or two before class on the days problem sets are due seem to be popular times for questions, but are difficult for me as I prepare for the lecture.  My email, phone, and office number are at the top of this page.


There will be regular (approximately biweekly) homework assignments that will count for 30% of the course grade.  You should anticipate spending a considerable amount of time on the assignments – this is, of course, where you will learn the most.   A few of the homework assignments involve computer programming.  As part of the coursework, I require use of a higher-level language such as MATLAB, Phython, IDL, or R Python because of their extensive data manipulation and display capabilities.  There will be two exams:  a mid-term exam which counts for 35% of the course grade and a final exam that counts for 35%.  Both examinations count as Major Grading Events as defined by the university.  A good number of the problems on these exams will be in the format of the Qualifying Examination for the Department of Astronomy.  As is usual for graduate classes, I expect that most students will receive an A or B.


Attendance and careful note taking is essential.  If you must miss a class, please arrange to get notes from one of your classmates and plan to come talk with me about points you find unclear.  If you know you will be away for university-related travel or religious holidays, please let me know as soon as possible (technically, within the first two weeks of the semester) so we can arrange alternate scheduling of homeworks or exams.   This same timeframe holds for students who need accommodation for documented disabilities.

Useful texts and references  

  We use two required texts, and a number of secondary texts that can be used as references to further clarify some topics.

Bruce T. Draine: Physics of the Interstellar and Intergalactic Medium
This wonderful book should be part of your library, and it is crucial for the first half of the course.

Frank H. Shu: The Physics of Astrophysics II
Perhaps not the most pedagogical, but a very useful conpendium on the theory of hydro and magnetohydrodynamics applied to astrophysics 

Additional texts  

James Lequeux: The Insterstellar Medium
A compact reference book on ISM, not as complete or expansive as Draine's, but useful.

Lyman Spitzer: Physical Processes in the Interstellar Medium
The classical reference book for any course in interstellar medium, it is outdated but still extraordinarily useful.

Donald E. Osterbrock: Astrophysics of Gaseous Nebulae and Active Galactic Nuclei
The reference for HII regions and optical spectroscopic diagnostics of ionized gas.