# Astronomy 126: The Interstellar Medium

## Archive of Assignments

### Week 13

*posted Nov 24*:

We'll read about and discuss the multiphase ISM this week. Here is the assignment for week 13 [pdf].

*posted Nov 19*:

We will discuss the remainder of the problems from the week 11 assignment during week 12. And, you should also take a look at this information about the hot intercloud medium.

### Week 12

*posted Nov 19*:

We will discuss the remainder of the problems from the week 11 assignment during week 12. And, you should also take a look at this information about the hot intercloud medium.

### Week 11

*posted Nov 10*:

We'll read about and discuss shock waves this week. Here is the full assignment for week 11 [pdf]. And here are some images and movies of shocks for you to take a look at:

simple animation of the sound-wave to shock-wave transition

snapshots and movies from simulations of shock waves

Cassiopeia A supernova remnant in X-rays

APOD images

shocks are subject to instabilities

like the Kelvin-Helmholz instability

schlieren photography of shocks

And here are the readings for this week:

sec. 2.2: thermodynamics [pdf]

sec. 4.1, 4.2: fluid equations and sound waves [pdf]

sec. 4.3, 4.4: shock jump conditions and shock structures [pdf]

sec. 4.5: strong spherical shocks [pdf]

### Week 10

*posted Nov 4*:

This week we are doing star formation. We'll read the beginning of Ch. 8 in Dyson and Williams, but several other things, too, including a short research paper. Your only pre-class assignment is to post a question in this Moodle forum about the paper by Monday night. There are worked problems too, but they're all due in seminar on Wednesday. Here is the full assignment for week 10 [pdf].

### Week 9

*posted Oct 28*:

Preparing for the midterm is your only assignment this week. Here is information about the midterm and a list of topics to study [pdf].

### Week 8

*posted Oct 21*:

Watch this "fly-through" of the Orion Nebula, based on Hubble data, to get a better sense of the spatial structure (and to, you know, imagine flying through the nebula!).

*posted Oct 20*:

This week is our second week for H II regions. We'll read and discuss the first half of a review article on the Orion Nebula and we'll read about density-sensitive line ratios in part of a chapter of *Astrophysics II: Interstellar Matter and Galaxies* by Bowers and Deeming [pdf]. The assignment [pdf] has some information to guide your reading of the Orion Nebula article (but no worked problems to hand in) and some information about the Bowers and Deeming article, and one worked problem from that reading (which you have to hand something in for on Tuesday). Note that I've also asked you to post a question on a Moodle forum about the Orion Nebula reading by Monday. And I've asked you to read this post about the Orion Nebula.

### Week 7

*posted Oct 13*:

This week is the first of two on H II regions (radiatively excited regions). We'll read Ch. 5 and work some problems related to the material there – some due on Monday and most due in seminar on Wednesday. Please read the assignment for week 7 [pdf] and come to seminar prepared to discuss any of the issues raised in that document.

### Week 6

*posted Oct 4*:

Post another round of questions and requests for discussion topics on this Moodle forum. And also choose a figure to present on in seminar in this Google Doc.

*posted Oct 2*:

Please post some questions, answers, and information about the abstract on this Google Doc I've shared with you. Make at least one annotation by Monday at 6pm, please.

I've also set up a general Moodle forum where you can post questions. Please also post at least one question there (about the body of the paper, not the abstract) by Monday at 6pm. I'll ask you to follow up with more questions after Monday evening. And please feel encouraged to answer each others questions or to ask follow-up questions.

*posted Oct 1*:

Most of our seminar meeting this coming week will involve a detailed discussion of a new, comprehensive paper on dust in other galaxies, *DustPedia - A Definitive Study of Cosmic Dust in the Local Universe*, Davies et al., arXiv:1609.06138, to appear in the Proceedings of the Astronomical Society of the Pacific.

I will soon post a formal assignment, with questions to think about/answer as you read the paper, perhaps some assigned presentation topics (likely focused on explaining the figures in the paper), and a mode for students to ask and discuss questions about the paper prior to our seminar meeting.

### Week 5

*posted Sep 23*:

The assignment for week 5 [pdf] is about dust. A few things to hand in on Monday and other things on Wednesday (plus a strong urging to bring notes on some other topics I enumerate in the assignment). We're reading Ch. 4 in D&W and also a short conference review paper by Bruce Draine. We will start the seminar meeting with continued discussion of the Boomerang Nebula.

### Week 4

*posted Sep 15*:

The assignment for week 4 [pdf] looks at heating and cooling processes in the ISM (and a temperature diagnostic, using real data). We're also reading and discussing a short paper on cooling (and temperature measurement) of a very, very cold place in the interstellar medium (Sahai and Nyman, *ApJL*, 487, 155). In addition to solving a few problems (and handing in your solutions – some on Monday and some on Wednesday), you also have to post a question about the paper by Monday, and then another one by Tuesday night. I've set up a discussion forum on our class Moodle page

### Week 3

*posted Sep 10*:

The assignment for week 3 [pdf] focuses in detail on the full transfer equation including emission as well as absorption. There are four problems to hand in at the beginning of seminar and one problem to hand in on *Tuesday*.

### Week 2

The assignment for week 2 [pdf] involves careful reading and preparation for detailed discussion in seminar of the material in the first six pages of Ch. 2. However, there are only two-and-a-half short problems for you to solve and write up your solutions for. And you will hand them in at the beginning of seminar. There are no Monday problems this week.

*posted Sep 2*:

Look over the images (and explanations) I showed in our first seminar. Review the D&W and Draine readings and the forum of questions and answers on the reading, as well as your four homework problems (soon to be graded and returned). The assignment from last week is available below. We will discuss all of these things in seminar during week 2. It may take up to half of our time. After that, we'll start in on *spectroscopy* and related concepts: line broadening, radiation transport, which we'll then finish up for week 3. The specific assignment will be posted here very shortly.

### Week 1

*posted Aug 23*:

Read the seminar guidelines posted in the Class Information section on the right side of the front page.

The assignment for our first seminar meeting is ready: week 1: Overview of the Galactic ISM [pdf]. The focus is the first chapter of Dyson and Williams. But you will also read a similar introduction to another, graduate-level, textbook. I've asked you to skim the ISM chapter of your Astro 16 textbook as well, and you'll use the textbook – as needed – for the short presentations you'll each give in order to help the seminar review some important physics topics that are relevant for our study of the ISM.

In addition to the reading and presentations, there are a small number of problems for you to solve. For some of them, your write-ups are due on Monday by 1:00 pm. The others you'll hand in at the beginning of seminar on Wednesday. The assignment also includes some questions and concepts for you to answer and think about in preparation for our discussion in seminar – I recommend you write down a few notes for these, but there's nothing to hand in. For the presentations, I'm asking you to meet briefly with me on Monday so we can review what you've put together. And finally, I'm also asking you to post one question about the reading by Tuesday night at 9:00 pm. All this information is detailed in the assignment pdf, linked above. The reading is available in Cornell Library (and I expect you all to have your own copies of Dyson and Williams by our first seminar meeting), but because many of you will not be on campus for a few days, I've made all the reading available on our seminar's Moodle page. Indicate your presentation topic choice there, too.

*from the summer*:

Each week's assignment and any associated reading will be posted here.

The first assignment will be posted no later than the Monday before classes start. And there will be something for you to hand in to me by the following Monday – two days *before* seminar meets.

Return to the main class page.

This page is maintained by David
Cohen

*cohen -at- astro -dot- swarthmore -dot- edu*

Last modified: December 13, 2016