AST 393F - Survey of the Interstellar Medium

Announcements Archive

5/2	:	If you have not yet filled out the Electronic Course Instructor Survey (eCIS), please do so by Friday afternoon (May 3). This feedback is important and will be used by the instructor and department when Ast 393F is taught again. We are now nearly finished with the semester. All homework has been graded and returned, and detailed solutions posted. There is only one oral presentation left, to be given in an abbreviated class meeting on Friday, May 3. Slides for most of the previous presentations are already posted. Most of you will have your Final Oral Exam next week; the schedule is posted on the Assignments page. For your convenience, the full question bank for these exams has been consolidated into a 2-page document on the Study Questions page. During the roughly 30-minute oral exam, you will pick (mostly randomly) from this set of questions; you should expect to answer approximately 5 - 8 questions, depending on the pace. I do intend to finish typesetting the course notes, hopefully before I forget what I covered! This may not happen until mid-summer, but I will let you know when they are complete.

4/19	:	We are now going through the oral presentations; slides are or will be posted on the Assignments page. Homework 3 should be turned in by 3:00 PM, Monday, April 22. The Study Questions for second-year exams are already posted. Most questions on the course oral exam will come from this list, although I may also ask one or two broader "what if" questions for discussion. Start thinking about when you would like to schedule your course oral exam, especially if you want to do it early, as practice for your actual second-year exam. Note that I will not be available any time on April 25 - 26 due to Nealfest. The last unit touched on a wide range of interfaces between different ISM phases and stars, as well as warm and hot ("coronal") diffuse ionized gas. Readings on these topics are widely scattered in the various books, and in some cases omitted. My recommendations for best sources are in bold face: Photodissociation Regions Tielens: ch. 9 Draine: ch. 31, pp. 346-356 (mainly H2) Osterbrock & Ferland: ch. 8 Shocks Dopita: ch. 8 & 11 (esp. fast shocks) Tielens: ch. 11 (esp. slow shocks) Draine: ch. 36 Hot (Coronal) Gas Dopita: ch. 5; ch. 7, pp. 143-153 Draine: ch. 34 Osterbrock & Ferland: ch. 11 Stellar Outflows Osterbrock & Ferland: ch. 10 - Planetary Nebulae ch. 12 - Novae & SNRs Kwok: ch. 15 pp. 440-454; ch. 16 Draine: ch. 38 & 39 Dopita: ch. 10 pp. 265-272

4/8	:	The second set of homeworks have been returned or are in your mailboxes, and Solutions are posted. The last few Study Questions have also been posted. End-of-semester oral exams will be based on the Study Questions, and if you included Ast 393F among your listed courses for the second-year exam, questions for that exam will be drawn from this question bank. The last homework problems of the semester, on molecules and dust are now posted. They are nominally due April 15, but if this is too close to your second-year defense or your oral presentation in Ast 393F, we can negotiate an alternate date. This homework set may look long, but I suspect it may take less time to actually work the problems than to read the questions!

3/27	:	The Atomic Spectroscopy reports have been returned, and are posted on the Assignments page, and one new homework problem has been posted. Also posted there is the schedule for the Oral Presentations, which start in three weeks. Reminder: April 25-26 are the dates for Nealfest. You may attend any of the talks and coffee breaks for free. However, if you want to partake of the meals, those are not free (see Kelly). We are now talking about Interstellar Dust. Although I am still working on catching up with the course notes, a preliminary outline and several useful Supplements are posted. Readings on Interstellar Dust Draine: chs. 21-26 Spitzer: chs. 7-9 Tielens: chs. 5-6 Dopita: ch. 12

3/15	:	The Course Notes are now complete through Section C: H II Regions. Two homework problems on H II regions are posted, and due Mar. 25. We will continue with IS Molecules the week of Mar. 18, although the notes that are eventually posted may not exactly match the content of Dr. Lacy's guest lectures. A draft schedule for the presentations of Student Project 2 has been circulated by e-mail. These will begin April 17 and continue after Nealfest. Other than the reports, I will assign (at most) 2 - 3 further homework questions. After Spring Break we will discuss plans to hold brief oral exams before the end of the semester. Readings on IS molecules: Molecular Energy Levels Draine: ch. 5, & 31 (on H2) Dopita:, pp. 24-39 Tielens:, pp. 29-45 Radiative Transfer, Molecular Clouds Draine: ch. 19-20; 32-33 Dopita: pp. 325-33

3/4	:	Because of overlap with assignments in other graduate classes, the due date for the Atomic Spectroscopy Project has been changed to 10 A.M., Wed., Mar. 6. The first batch of homework problems, numbers 1 - 3, has been graded and returned, and Solutions are now posted. A couple of homework problems on H II regions will be assigned before the end of the week, and you'll have 2 weeks to complete them. We are now talking about Interstellar Molecules, starting with guest lectures this week by John Lacy. Relevant readings are: Molecular Energy Levels Draine: ch. 5, & 31 (on H2) Dopita:, pp. 24-39 Tielens:, pp. 29-45 Radiative Transfer, Molecular Clouds Draine: ch. 19-20; 32-33 Dopita: pp. 325-33

2/26	:	The due date for the Atomic Spectroscopy Project has been moved back to Mon., Mar. 4. That is also the date when new homework problems, on H II regions, will be distributed, and when we will move on to the topic of Interstellar Molecules, starting with several guest lectures by John Lacy. Course Notes have now been posted through Thermal Equilibrium, Section C-2. Notes on the recombination spectrum are coming, as well as a couple of Supplements. The recommended sections of our various reference books were posted in the previous announcement and can be looked up in the Announcements Archive.

2/21	:	I have begun posting notes for unit C. H II Regions. My favorite source for this subject is Osterbrock's book, any edition (see below). We will continue with H II regions through next Monday or (probably) Wednesday, and then will move on to Interstellar Molecules, to be covered by John Lacy. The current assignment, due Friday, March 1, is the Atomic Spectroscopy project. I have added a link to the Atomic Line List site on the Links page. This can be quite a useful tool, although it's a bit complicated to use; I'll give a brief demonstration in class tomorrow (Feb. 22). Recommended Readings on H II Regions: Osterbrock & Ferland: chs. 2-5 for the basics; other chapters according to interest Tielens: ch. 7 Dopita: ch. 6; also pp.42-53, 72-75, 82-85; ch. 9, pp. 219-25; 233-45 ch. 10, pp. 249-54; 260-63 Draine: ch. 15, 27, 10, 14, 18 (roughly by order in which these topics will be covered)

2/11	:	Another section of the notes, on the H I 21 cm line, has been posted, with a few more pages to come. Then we will move on to our section on H II regions. The primary reference book for this topic is Osterbrock & Ferland, although I will be posting my own notes as well. Two additional homework problems were given out on Mon., Feb. 11, and are due at the beginning of class on Mon., Feb. 18. For uniformity, the previously assigned problem on O I will now also be due on Feb. 18, instead of Feb. 15 as previously announced.

2/1	:	The week of Feb. 4, we turn our attention to observational methods and results for H I regions. Some pages of notes are posted. There is not a lot of detail in most of our reference books on this topic; Draine has the most (see below). Also posted are the assignments handed out today, in case you didn't pick up a copy or lose them. The first of a few homework problems due two weeks from now is posted, as well as the first project (spectroscopic case study), due in about four weeks. Draine: ch. 6 & 9 for optical/UV absorption lines; ch. 7 & 8 for the H I 21 cm line Dopita: pp. 59-67; 75-77 Tielens: pp. 308-310; 304-306 Kwok: ch. 5, esp. pp. 136-142; 156-157

1/28	:	Today we started on atomic spectroscopy, and another batch of pages is (about to be) posted on the Course Notes page. The thought question I gave at the end of class was: Consider two lines emitted by ions present in the ISM. Assume the energies of the upper levels relative to each ion's ground state are the same, and that they are similar in all ways except that one is an electric-dipole permitted line (large Einstein A value) and the other is a forbidden line (smaller A). The gas has low density but the upper levels are nevertheless populated by collisions. How is the ratio of the line brightnesses related to the ratio of A values? Are there other parameters that might be important? (Hint: This is a trick question!) Reading ahead in the reference books (if you're interested): Draine: ch. 17 (esp. 190-98) Dopita: ch. 3 Tielens: 46-53

1/25	:	Several more pages are (about to be) posted, covering through today's discussion of pressure-balanced phases in the ISM (see pdf link after line 3d of the Course Notes Outline). Pages for relevant readings can be found in the Announcement Archive. On Monday (Jan. 28) we will take a brief look at atomic structure and spectra, reviewing some generic patterns and potentially observable spectral lines. The instructor's notes on this topic are currently being converted from handwritten to typeset format; in the meantime I recommend one or more of the following: Draine: ch. 4 (all = pp. 32-37); also 60-62 Dopita: ch. 2 (esp. 20-24) Tielens: 25-29 Kwok: 78-85; 103-124

1/22	:	We are up to page A-10 in the course notes, and this week we will tackle the topics of heating & cooling and thermal "phases," with emphasis on the neutral ISM ("H I regions"). We now have complete sets of the main reserve books in both Peridier and the PMA libraries. The following sections are of interest for this week, with the most relevant pages listed first. Draine: ch. 30, esp. pp. 337-43; also 182-86 Tielens: ch. 8, esp. 269-77 & 282-83; also 54-49, 63-71, 80-82 Dopita: ch. 14, esp. 343-355

1/17	:	We are devoting the first couple of weeks of this class to an overview of the ISM, starting with specifying the relevant thermal properties (n, T, P) and what factors determine their values. We're also addressing some of the usual assumptions about what governs the state of the gas (and in some cases questioning their validity!). Course notes from a previous incarnation of this class will be posted in segments, with updates and digressions posted as Supplements; suggested readings in the various reference books will also be posted.