Astr 640 Class News & Information

FINAL EXAM, Friday May 13.

- Help improve this course! Astr640 Questionnaire in .pdf format. Keep in mind that in order to spend more time on a topic, less time is available for other topics. I appreciate your feedback and help - it is very valuable and makes the class better!


May 7:
- Notes on accretion disk structure. (The .pdf format provides major compression compared to .ps in this case.)
- Here are some mpeg animations of interacting binaries:
(I made the first three using Rob Hynes software "binsim". I don't know why the stars are olive green....!)
+ Cataclysmic variable animation.
+ Quiescent X-ray binary animation; Notice the corona and ADAF "hole" in the disk.
+ Outburst (SXT) X-ray binary animation; the disk now extends right down to the compact object and a jet has formed. Notice the strong irradiation of the secondary star (and the disk shadow).
+ Magnetic cataclysmic variable (IP) animation.
+ XRB hydrodynamic disk simulation; this animation is from the Leicester (UK) accretion disk group.

Apr 27:
Think about the following:
An early type star (O or B star) is much more luminous than an M star (even more so for the L and T stars). Not surprisingly, the spectrum of an early type star looks extremely different than the spectrum of a late type star. Look at some stellar spectra to remind yourself of this dramatic difference. Now consider AGN. The most luminous AGN are many thousands of times brighter than the least luminous AGN. And yet their spectra are remarkably similar. Sure, there are some line ratio changes, but the same lines are present; this is nothing like the totally different spectra beween M and O stars. Look at the Sloan DSS Redshift Gallery of AGN to remind yourself. Indeed, the spectra are so similar, a composite spectra of different AGN combined together is sometimes used as "THE spectrum of an AGN". There are variations in line widths, and some changes in line strengths, but the spectra are quite similar. Any thoughts as to why?
The main thing is that the emission is driven by photoionization. This leads to the concept of the ionization parameter, U. The ionization parameter is really just the ratio of the number of photoionizing quanta to the number of ions in the gas. For reasons that are not completely understood (at least not to me!), U is fairly similar in different AGN, with U ranging from about 0.001 to 0.1. Because U issimilar in different AGN, the AGN SEDs are similar.
- Suggestions on how to give a professional talk: "talk-criteria.pdf"

Apr 13:
- Because Term papers are due next week, HW #8 is due in 2 weeks, not 1 week.
- Don't go overboard on HW #8.3 - just use the published figure of the line intensity ratio in Peterson's book (or Osterbrock & Ferland) to get the electron number density.
- Probable typo in Peterson's book, p 77: Case B recombination coeff: alpha_B = 1.43 x 10^-13, not 2.52 x 10^-13.
- I believe there is a typo in Peterson's book, p. 88: I don't see the need for the "2" in the expression V = 2 pi l² r₁.
- Quick notes on the Kerr BH and the ISCO.
Thoughts and Notes on the CCF:
- Like a Fourier transform, the ccf does not include error bars. This can be a limitation/weakness in some cases.
- While you can compute the CCF using a FFT (and then take the inverse FT to go from the frequency domain to the time domain), for the small number of points we use in AGN reverberation problems, it is much easier to just compute the CCF directly in the time domain.
- The point of the CCF homework is for you to learn how the CCF works in practice. Just as with Fourier transforms and power spectra, the discrete and finite CCF is very different from the mathematical CCF (infinite and continuous). The point is not to be a programing excercise. So if you are really pressed for time and have access to a reliable CCF code, then go ahead and use it.
- At the risk of not being modest, here's a reference on using the CCF for AGN echo mapping: On the Reliability of the Cross-Correlation Function Lag Determinations in Active Galactic Nucleii. This paper has been called "CCFs for Dummies" by a colleague who works on AGN variability.

Apr 5:
- For those interested in nebulae, THE book is ``The Astrophysics of Gaseous Nebula and Active Galactic Nuclei'' by Don Osterbrock and Gary Ferland, University Science Books, 2006. This book is affectionately known as "AGN²".
- Reminder: Term Paper due date: Friday Apr 22 (at 1 pm)
- Term Paper reminders/hints: The term paper should be as technical as possible: DON'T make this an astro 101-level paper or even an undergrad-level paper! This should be graduate/professional-level work. Include equations, derivations, figures, etc.. Be sure to have a thorough bibliography. The Term Paper is worth 15% of final grade, so it should take about 1/6 of all the effort you put into this course.
- For your term paper, be sure to use the ApJ style for references, citation, etc..
- Figures and Tables do not count against the 3-page limit.
- Remember that all figures should be in Encapsulated PostScript format. Use plotone, plottwo, or plotfiddle to include the figures in your LaTeX file.
- Some advice on emulateajp style file usage: First, get your draft paper to properly format under AASTeX. Then, once you have all the kinks worked out with creating the .ps files, figs, etc., then use the emulateapj style file.
- - More hints on emulateapj: Put all files in the same directory as your .tex file when you run LaTeX. You don't need to do anything else, except alter the first line in the .tex file (see below). This will make your paper look very similar to the actual ApJ format. Reminder: the paper format MUST be formatted this way. The first line of your LaTeX file should be this:
\documentclass[preprint2]{emulateapj}
Of course, you need to have the emulateapj style file in your directory too.
- - The emulateapj font size and spacing are very compact, meaning that 3 pages in this ApJ style is a lot more than 3 pages in normal LaTeX mode or even the aastex preprint2 style.

Mar 16:
- Reminder: Midterm Exam on Wed, March 23
- Reminder: The Term Paper must be in ApJ Letters format, and this will require you to be fluent in LaTeX. There will be no formal instruction on LaTeX in this course. Links to the ApJL style files are located on our class Astr 640 home page.
- When reading Ch 8 of Frank, King, and Raine, don't worry about the set of equations in section 8.1; we'll go over these later in the course and you don't need them to understand this chapter.

Mar 9:
Here are two recent very nice "big picture" review papers (in .pdf format):
- Active Galactic Nuclei and Quasars, 2010-2020 Science White Paper for the 2009 NRC Decadal Review by Elvis et al.
- The Origins and the Early Evolution of Quasars and Supermassive Black Holes by Djorgovski et al.
A great web site on Magnetars, Soft Gamma Repeaters & Very Strong Magnetic Fields by Robert C. Duncan, University of Texas at Austin
Additional Reading: ``Introduction to Unified Schemes'' by Wills B.J. in ``Quasars and Cosmology'', A.S.P. Conference Series (1999), eds. G.Ferland, J.Baldwin (San Francisco: ASP): astro-ph/9905093.

Feb 23:
- We are extending the due date for term paper topic proposals from March 1 to March 4. Present a short (< 1 page) typed "proposal" for your topic including a partial bibiography. The proposal does not have to be in LaTeX. (NB: If you are preseting research at the SRS, you can turn in your paper proposal on March 7th.)
- Please read John Kormendy's "Supermassive Black Holes in Galactic Nuclei" web page.

Feb 16:
- You can get the article Infrared Adaptive Optics Reveals Stars Orbiting Within Light-Hours of the Milky Way's Center by Bertram Schwarzschild in Physics Today 2003 February via the link: http://www2.physics.umd.edu/~jacobson/171c/ourbhart.htm
- Related to observations of Sag A*, for those interested in learning more about speckles and atmospheric seeing, check out the following pages:
-- Nick Strobel's Astronomy Notes on Seeing
-- "Techniques of Observational Astronomy" by John Oliver
See also:
-- A very nice set of notes by Jon Holtzman from his Astronomical Techniques course at New Mexico State University.

Feb 9:
- For homework #3, you can ignore GR effects other than gravitational redshift, as they don't come into play. For example, Q2 asks what energy is released upon impact; it does not ask what luminosity is seen by an observer far from the NS - that would require consideration of GR effects. BUT don't ignore special relativity unless it is justifiable.
- Formerly known as Constellation X and then merged with ESA's XEUS, the International X-ray Observatory is the next generation premier X-ray observatory. Read the aims of the mission here: IXO: Science Goals. In particular, read about the example science investigation: How does cosmic feedback work and influence galaxy formation?

Feb 2:
When reading Accretion Power Ch 2.1-2.4, don't worry too much about the details - just try to get a feel for what's going on. Pay attention to the meaning of the sound speed, as we will see this over and over. Although it is mathematically elegant, we are going to skip section 2.5 on spherical accretion (also called Bondi-Hoyle accretion) because it has limited astrophysical consequence (and we've plenty of other things we need to get to!). Likewise, we are going to skip Ch 3.
If you want a head start, the next reading assignment after Ch 2 will include Ch 7.1-7.6 in Frank, King & Raine.

- Sag A*: Galactic Center Research at MPE (Max-Planck-Institut für extraterrestrische Physik), Germany
Galactic center animated gif "movie" from the MPE group (small mpeg "movie")
- More on the SMBH at Sag A*:
Prof. Andrea Ghez and the UCLA Galactic Center Group
An animation of stellar orbits in the central pc (from the UCLA Galactic Center Group).
And from the GCNEWS - A Newsletter for Galactic Center Research:
- Recent Advances Made with a Decade of Diffraction-Limited Data From the W. M. Keck 10 meter Telescopes A. M. Ghez
- On the Road Toward a Deeper Understanding of Sgr A* and its Environment R. Schoedel, R. Genzel, F.K. Baganoff, & A. Eckart

Jan 26:
- For those who need some help with LaTeX, see my web page for Astr 680 and look under the title "More Tools and Resources" (about 2/3 down the page). You'll find a sample LaTeX file with a minimal set of instructions on how to use LaTeX. There's other info there that might be of use to you too.
- Suggestion: Get the astro-ph preprint version of the NGC 4258 Herrnstein, et al. paper on the arXive preprint server: astro-ph/9907013. For the Myioshi et al paper, you'll need to get a copy from the library, since the journal Nature does not allow its articles to be availabe on the ADS. (See me if you'd like to use this to earn your class participation by getting a copy from the library.)
- A very nice website about AGN: Bill Keel's (University of Alabama) rich source of images and notes on Quasars and Active Galactic Nuclei. In particular, take a look at the following pages: (i) Optical spectra of various kinds of active galactic nuclei and (ii) "...Joe Miller once mused that we didn't know whether quasars were merely interesting, or actually important." Find out the answer at: Quasar Astronomy Forty Years On

Jan 19:
For every homework question, think about the purpose of the question. What is the deeper meaning? Getting the right answer is only part of the questions. The main part is to think about what this means: what are the implications?
- From Level 5 "A Knowledgebase for Extragalactic Astronomy and Cosmology", here is Chapter 1 of Peterson's "An Introduction to Active Galactic Nuclei"
- Sample of Sloan Digital Sky Survey SDSS quasar spectra
- Supermassive Black Holes in Galactic Nuclei by J. Kormandy at the Univ. Texas, Austin.
- A nice history of the Hubble Constant by John P. Huchra at the CfA.
- NED - the NASA/IPAC Extragalactic Database.


Term Paper Information
Term papers should be in depth and detailed, not an overview of a topic. It should be as specific as possible. Use equations and figures as necessary. It should be at the graduate-level, not at the Astr 101-level.
Papers must be written in LaTeX using the ApJ Letters format, with a maximum length of 4 pages (including everything except figures).

Some ideas for topics and additional information for the term paper.

Here are explicit instructions on how the Term Paper should be written and also on how it will be evaluated:
"paper-criteria.pdf"

Late Term Paper Policy:
1/3 letter grade deducted per day late.
Maximum penalty is 1-1/3 letter grades, which applies to all papers submitted 4 or more days late.