AS4011 The Physics of Stars and Nebulae I

AS4011 The Physics of Stars and Nebulae I

Kenny Wood (kw25)

This course presents an introduction to the study of radiation transfer, evolution of HII regions (dynamics and thermal equilibrium), emission line diagnostics, and Monte Carlo radiation transfer techniques. The lectures outline the material covered in the course and that which is examinable.

The first part of the course on basic radiation transfer terms and the equation of radiation transfer follows the relevant chapters in the Rybicki & Lightman textbook. The lectures covering the development of HII regions and on determining physical properties of nebulae and the intersetellar medium follow the chapters covering the same material in the textbooks by Bruce Draine and Osterbrock & Ferland. I'll be presenting a few lectures on Monte Carlo radiation transfer techniques that I use extensively in my own research on circumstellar disks, stellar coronae, planetary atmospheres, galaxies, HII regions, the interstellar medium, and medical physics.

There are four tutorial sheets and an example "exam style" question. Please also see the Revision Quiz questions that are at the end of each lecture. Several in-class tutorials will be arranged to go over questions from the Revision Quizes, tutorial sheets and other questions arising throughout the course. The Revision Quizes and tutorial questions will not be formally graded or contribute to the module assessment, but students are strongly encouraged to work through the Revision Quizes, tutorial sheets, past exam papers, and the relevant chapters in the recommended text books.

Along with the lectures and tutorials, there is a continually assessed component to the course and this will comprise a problem set on Monte Carlo radiation transfer techniques. This will comprise 25% of the module assessment.

Prerequsites are AS2001 or AS2101. Computational Physics and/or Computational Astrophysics are recommended and will be very useful for the continually assessed component of the module.

Recommended Reading

Radiative Processes in Astrophysics by Rybicki & Lightman

Physics of the Interstellar and Intergalactic Medium by Bruce Draine

Astrophysics of Gaseous Nebulae and Active Galactic Nuclei by Osterbrock & Ferland

Introduction to Monte Carlo Radiation Transfer by Wood, Bjorkman, Whitney & Wolff PDF
This is a short booklet that we prepaperd on basic Monte Carlo radiation transfer techniques. A plane parallel isotropic scattering code and some three dimensional scattering codes are available here.

Lecture Notes

PDFs of the lecture slides are available with two slides per page. The Power Point files containing audio on each slide are available as read-only pptx files.

Lecture 1: Quantities PDF

Lecture 2: More quantities PDF

Lecture 3: Radiation transfer PDF

Lecture 4: Blackbody emission PDF

Lecture 5: Spectral lines PDF

Lecture 6: Einstein coefficients PDF

Lecture 7: Detailed Balance PDF

Lecture 8: Linew widths PDF

Lecture 9: Saha Equation PDF

Lecture 10: Free-Free Scattering PDF

Lecture 11: Random Walk PDF

Lecture 12: Monte Carlo Basics I PDF

Lecture 13: Monte Carlo Basics II PDF

Lecture 14: Fine Structure PDF

Lecture 15: HII Regions PDF

Lecture 16: Ionization Fronts PDF

Lecture 17: Thermal Equilibrium PDF

Lecture 18: Case A and Case B PDF

Lecture 19: Temperature & Density Diagnostics PDF

Lecture 20: Star & nebula diagnostics PDF

MNRAS paper on collision strengths: PDF

Some derivations...

In the class some results are stated without detailed derivations, such as the Lorentz and Voigt profiles for line absorption cross sections, and Kramer's approximation for continuous absorption. Various approximations and assumprions are used to derive these formulae, such as treating an atom as a damped harmonic oscillator. Detailed derivations are given in the recommended textbook Radiative Processes in Astrophysics by Rybicki & Lightman. Also, Chapter 4 of the textbook Stellar Atomspheres by Dimitri Mihalas (WH Freeman & Co., 1978) is devoted to absorption (and scattering) cross sections and derivations can be found there.

Continually Assessed Component

Monte Carlo exercise sheet PDF

You may wish to use the random number generator ran2.f from Numerical Recipes for the exmple sheet problems.

Tutorials and Solutions

Tutorial 1: PDF Solution

Tutorial 2: PDF Solution

Tutorial 3: PDF Solution

Tutorial 4: PDF Solution

Exam style questions: PDF