The Milky Way Galaxy

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This course is given by prof. J. Blommaert. It is given in 13 2-hour sessions, one of which is used to make exercises. Lecture notes consist of the book "Galaxies in the Universe" by Sparke & Gallagher, slides and some copies of another book. For the exam, only the slides have to be studied. The exam is closed book, and only written. It consists of a lot of questions and subquestions, covering the whole course. Some of the derivations that are in the slides can be asked, and the professor has also pointed out the importance of the exercises. The exam accounts for 14/20, while the two assignments given during the semester account for 3/20 each. Don't forget your calculator on the exam, and most important: keep track of the time!


24 January 2008


  • Describe the hubble tuning fork sequence. What is its main use, and can it be seen as an evolutionary sequence? What are the main problems of classification of the different galaxy types?
  • What is the gas content of different galaxy types? How does this explainthe difference in optical spectra of the 3 main galaxy types?
  • Classify the spectra in the figures, and explain your criteria. What can you say about the starformation history of these galaxies?
  • Explain how the Tully Fisher relation can be used to determine the distance to spiral galaxies.
  • What galaxy types do we find in the local group? What is Hubble type of our own galaxy? Explain the characteristics that lead to this classification.

Star Counts

  • Describe the predictions of star counts and observed brightness in the galaxies for the case of uniform space density of D stars per cubic parsec, our galaxy is infinite and without extinction.
  • Discuss on base of your result the assumptions that where made.
  • What was the reason to assume 2 disk components in our galaxy? On what further evidence was the separation in 2 different components further substantiated?

Chemical Enrichment

  • What are the assumptions made for the Closed Box model?
  • Derive an expression for the mass in stars with metallicity lower as Z for the closed box model.
  • Explain what the G dwarf problem is, and give possible solutions.

Interstellar Medium

  • What is the origin of the 21cm line of HI emission? Why is it not possible to measure this directly in a laboratory?
  • What is the local standard of rest? How can HI measurement be used to determine the rotation curve of the Galaxy? What are the advances of using HI? What do we deduce from the fact that the rotation curve remains constant i.f.o. galactic radius?

10 June 2010

Distance Determination

  • Describe the Baade-Wesselink method in detail.
  • Exercise 2.7 from SG, about the SN ring.

Chemical Enrichment

  • What are the assumptions made for the Closed Box model?
  • Derive the Leaky Box model with g(t) = c dMs
  • Why are the bulge stars relatively richer in alpha elements than in iron, compared to the disk stars?

Interstellar Matter

  • Explain figure 2.20 from the book (figure was given) knowing formula 2.11
  • Using the previous question, how can you obtain the rotation curve?
  • Why do we use HI for this and not CO? And what can you tell about the distribution of CO/HI in the galaxy

Other Galaxies

  • Describe M32 and M33
  • Describe strong encounters. Is it relevant for the solar neighbourhood (values of solar mass, etc... are given)
  • Give a not to elaborate description of Dark Matter in spiral galaxies
  • What are isophotes? How are they used to classify ellipticals in the Hubble sequence? What is good/bad about this method? Explain twisty, boxy, disky. What do these terms tell us about the galaxy, apart from it's structure.
  • Describe how the unification paradigm explains the difference between Seyfert I and II.