AST1440. Radiation Processes and Gas Dynamics
A graduate course at Dept. of Astronomy & Astrophys., U of T


Syllabus with a timetable of lectures and exams (text file).
Lectures and tutorial/project meetings will start 20 Sep. 2016, and continue until early Dec.,
on Tuesdays in AB113 1pm -3:40pm (max 4pm) in AB113 (next to Cody Hall).

Contact info

Prof. Pawel Artymowicz (homepage) has offices in the Physics Tower rm 1208, tel 416-946-5719, and at UTSC, Science Wing rm 506, 416-287-7244;
Urgent matters: call 416-358-4275. Email pawel(AT) (please indicate AST 1440 in the subject)

Scope of the course

The course covers essential knowledge of the radiation and of gas dynamics It consists of 11-12 meetings of 2 hr duration (with a break). In addition, we sometimes spend 30 extra minutes discussing numerical projects or assignments. Most of the meeting, I am talking. Some of the meeting, you prepare from the books and papers and present the topic.

Radiation can be black body radiation, line radiation, synchrotron radiation and other types freqently encountered in low- and high-energy astrophysics. But since talking about radiation alone (moving in vacuum) can be done in 15 minutes or so, we spend most time on interaction of radiation with matter. That matter is usually astrophysical gas or plasma, either in a stellar object or diffuse medium, but importantly also with solid matter (particles of dust and surfaces of larger objects). The latter is often skipped in courses such as this, but is necessary to model the appearence of planets, cool stars, circumstellar disks, ISM and galactic disks - all cold objects where heavy elements precipitate to solid state below T~2000 K.
Gas dynamics will be discussed both apart from and in connection with radiation, in astrophysical contexts emphasizing spherical objects and disks (axisymmetric and not). Theory and some observations will be discussed, with a clear predominance of the former.

Exam & grading (out of 10p.)

3p. for a couple sets of assignments. These problems will involve no substantial computation. They'll be given after completion of project 1.
2p. for an oral exam at the end of the course. < 30 min in duration, it will provide a valuable training before a qualifier exam.
3p. for 2 projects involving substantial programming (cf. topics below). They are more ambitious and time-consuming than the assignments. They replace the midterm and the final written exams. You'll have about 4 wks. to complete each, but I'll check your progress and we'll discuss issues at tutorial meetings.
2p. for study and presentation of two subjects (20 min and 40 min. informal lecture-style presentations). The presentations will be placed on a hidden webpage for viewing by course participants only.


  1. "Radiative Processes in Astrophysics", Rybicky & Lightman, Wiley 1979.
  2. "Radiative processes in high-energy astrophysics" by Ghisellini, (Lect. Notes in Phys. 873), Springer Verlag 2013
  3. "The Physics of Astrophysics II. Gas Dynamics" by Shu, U. Sci. Books 1992.
Additional books you may want to read (consult with me before buying texbooks or these books)

Some lecture notes and papers

Goldreich and Tremaine 1979, seminal paper on linearized disk dynamics
Jeffrey_Fung_thesis.pdf , a recent PhD thesis at our department, relevant to the course

Some interesting problems to think about

Here are the problems so far. Let's discuss their solutions during our next meeting. Be prepared - you will be asked about the way you solved them!

Numerical Projects

You'll be offered some choice of other topics in case you already have experience with these (1 & 2 are obligatory, those of you that had previous experience with similar projects may proceed beyond these two.)
  1. Radiatively forced particle disk dynamics and instabilies
  2. Smoothed Particle Hydrodynamics, applied to SMBH binary merger problem
  3. Gas accretion onto astrophysical objects, e.g. BHs, planets
  4. Mie theory and the simulated appearence of dusty objects (disks)
The final outcome of each project is a short writeup of main techniques, results, and analysis, 5 pages including figures + an animation would be a goal here.

Project #1

See this
description ; last updated 17 Oct, including deadlines

Project #2

See this description ; last updated 17 Oct, including deadlines

Suggestions for your in-class presentations

I'd like everybody enroller in the course to do one short (20 min max) presentation of a smaller topis, most of them straight from the textbook, and one longer (40 min). Smaller topics have been distributed by now, and include: Black body radiation laws, Polarization, Radiation from moving charges, Synchrotron and Bremsstrahlung radiation, Einstein coefficients, Eddington approximation.

The larger reading projects are:

  1. Radiation from acretion disks in diiferent approximations and models
  2. Coanda effect: why? Vorticity, airplanes and all that
  3. Bremsstrahlung vs. Synchrotron radiation - what's more interesting?
  4. Beaming and Blazars
  5. Radiation pressure on dust in disks
  6. Photophoresis and spinning dust - can we compute it?
  7. Scattering and absorption by nonspherical particles - can we compute it?
  8. Essential similarities of all turbulent jets in hydrodynamics
  9. Magnetized jets in astrophysics
  10. 1-D Parker model for stellar wind and its MHD extensions
  11. What is Smoothed Particle Hydrodynamics
  12. Gas accretion onto astrophysical objects, e.g. WDs, BHs, planets
  13. your favorite topic (if approved by lecturer)

Links provides many interesting implementations of Mie and generalized Mie theories, codes and hopefully some ideas for astro applications. is other Mie site, providing online calculator of phase functions and more, but for aa single particle and single wavelength at a time provides lots of informations on Mie theory, sigle scatterng, meteo phenomena such as rainbows, haloes, and more

last modified: Sep 2016

background image: Radiation from HL Tau disk, which is optically thick in visible, optically thin at mm-wavelengths, at which the intriguing structure of its disk was imaged in 2015 by ALMA. The structure is due to gas+dust+radiation(+planets?) dynamics.