1. Announcements The final exam will be at Noon on Monday, December 13 in Van Allen Hall LR1. Practice questions for unit #5 are available on the class web site. Friday will be a review. Extra office hours: Thursday 10-11 am, Friday 9:30-10:30 am.

2. The Large Scale Structure of the Universe Clusters of galaxies X-rays from clusters of galaxies Sheets and voids

3. Review questions How can fluctuations in the cosmic microwave background be used to determine the geometry of the Universe? What are the major components and their fraction of the total mass/energy in the Universe?

4. Temperature variations in the Cosmic Microwave Background (CMB) are observed to be about 0.0003 K. The expected physical size of the hot/cold regions can be calculated.

5. Contents of the Universe

6. Our Galaxy is a member of a small cluster called the Local Group

7. Stephane’s Quintet

8. Virgo cluster

9. Abell 2218

10. Coma cluster

11. Coma cluster in X-rays

12. Coma cluster X-ray emitting gas is at a temperature of 100,000,000 K. The total X-ray luminosity is more than the luminosity of 100 billion Suns. From this, the amount of X-ray emitting gas can be calculated. The mass of X-ray emitting gas is greater than the mass in all the stars in all the galaxies in the cluster.

13. Gravitational lens

14. Gravitational lenses By measuring multiple images of one source, we can figure out the total mass in the lens. This provides an independent confirmation of dark matter. A lense can act as a huge telescope. The deepest images of the most distant galaxies are obtained with clusters acting as gravitational lenses.

15. The red Galaxy is 13 billion light years away. We are seeing it 750 million years after the Big Bang.

16. What evidence do we have for the existence of dark energy? 1.It blocks our view of distant parts of the universe. 2.The universe contains more mass than can be accounted for by stars. 3.The expansion of the Universe seems to be accelerating. 4.We see the cosmic background radiation in all directions.

17. Large Scale Structure Are clusters of galaxies the largest structures in the Universe?

18. Million galaxies

20. Structure in 3d

21. Large Scale Structure Galaxies and clusters of galaxies are organized on irregular sheets separated by voids containing few galaxies. The density fluctuations seen in the cosmic microwave background are likely the seeds for the formation of the sheets, clusters, and galaxies. How that process occurs is now being worked out.

22. Simulation of Structure Formation Movie

23. The End