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Dr. Gregory Rudnick (NOAO/Kitt Peak)

RECIPE FOR A GALAXY CLUSTER: A LOT OF DARK MATTER, A BUNCH OF HOT GAS, AND A SPRINKLING OF GALAXIES. Dr. Gregory Rudnick (NOAO/Kitt Peak). Some BIG questions about galaxy clusters?. What are they? How do they form? Where do they live? Why are they interesting?

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Dr. Gregory Rudnick (NOAO/Kitt Peak)

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  1. RECIPE FOR A GALAXY CLUSTER: A LOT OF DARK MATTER, A BUNCH OF HOT GAS, AND A SPRINKLING OF GALAXIES Dr. Gregory Rudnick (NOAO/Kitt Peak) Steward Observatory – Gregory Rudnick

  2. Some BIG questions about galaxy clusters? • What are they? • How do they form? • Where do they live? • Why are they interesting? • What are some current efforts to study them? Steward Observatory – Gregory Rudnick

  3. A review of gravity • Gravity is a force • Everything attracts everything else • Without gravity everything would move in straight lines Steward Observatory – Gregory Rudnick

  4. What are galaxy clusters? Large groups of galaxies held together by gravity. 6 Million light years Steward Observatory – Gregory Rudnick

  5. What are galaxy clusters? Large groups of galaxies held together by gravity. Ben Moore Steward Observatory – Gregory Rudnick

  6. What are clusters made of? Hercules cluster galaxies Steward Observatory – Gregory Rudnick

  7. An Interlude: Galaxies 101 (in 3 minutes) Galaxies are large collections of stars with gas and dust There are hundreds of billions of stars in every galaxy That’s about 200,000,000,000 stars!! Steward Observatory – Gregory Rudnick

  8. Hundreds of galaxies • That’s trillions of stars!! • Elliptical and S0 galaxies are the most common types of galaxies Steward Observatory – Gregory Rudnick

  9. How massive are clusters? • Use motions of galaxies. • Calculate how much mass you need to hold cluster together. clusters are 1015 times as massive as the sun Stars make up only 5% of cluster mass! Where is the missing mass? Steward Observatory – Gregory Rudnick

  10. Stars aren’t the only game in town • Matter emits at other wavelengths too. • Hot (10 million degree) gas emits in the x-ray • Twice as much hot intra-cluster gas as stars • Hot gas makes up 10% of total mass Steward Observatory – Gregory Rudnick

  11. Gravitational lensing Where is the rest of the mass? • Only 5% stars + 10% hot gas has been seen • Where is other 85%? • Can we verify the large mass? Galaxy clusters are mostly made of “Dark Matter” Steward Observatory – Gregory Rudnick

  12. What do we know • Clusters are made of: • galaxies (5%) • hot gas (10%) • dark matter (85%) Steward Observatory – Gregory Rudnick

  13. How do they form? volker springel Steward Observatory – Gregory Rudnick

  14. Where do clusters live? The nearest two clusters Coma (260 million light years) Virgo (55 million light years) Steward Observatory – Gregory Rudnick

  15. The Big Picture Steward Observatory – Gregory Rudnick

  16. The Big Picture Steward Observatory – Gregory Rudnick

  17. Why are clusters interesting and useful? Providing evidence for dark matter Gravitational lensing Steward Observatory – Gregory Rudnick

  18. Steward Observatory – Gregory Rudnick

  19. The Bullet Cluster - testing the existence of Dark Matter If gravity is stronger on large scales and dark matter doesn’t exist then the gravitational force should be located at the center of the “visible” matter. Douglas Clowe Steward Observatory – Gregory Rudnick

  20. The Bullet Cluster Use gravitational lensing to measure total mass. Douglas Clowe Steward Observatory – Gregory Rudnick

  21. Clusters as Laboratories of Galaxy Evolution Can clusters tell us how galaxies might transform their types? How can a spiral turn into an elliptical? Steward Observatory – Gregory Rudnick

  22. Ram Pressure Stripping What happens to gas in a galaxy when it flies through the hot intra-cluster gas Steward Observatory – Gregory Rudnick

  23. Galaxy Harassment Steward Observatory – Gregory Rudnick

  24. Galaxy Harassment Steward Observatory – Gregory Rudnick

  25. Observing the Evolution of Clusters How can we see clusters when they were younger? Astronomy is like archaeology. increasing distance back in time Steward Observatory – Gregory Rudnick

  26. CL1037.5-1243 5.3 Billion years CL1054.4-1245 6.3 Billion years CL1354.1-1231 6.3 Billion years CL1202.4-1224 4.3 Billion years CL1232.3-1250 5.1 Billion years Clusters through cosmic time Steward Observatory – Gregory Rudnick

  27. cl1037-1243 5.3 Billion years cl1216-1201 6.5 Billion years Galaxies in Young Clusters Steward Observatory – Gregory Rudnick

  28. Summary • Galaxies don’t matter: Clusters are dominated by Dark Matter (5% stars, 10% hot gas, 85% dark matter) • Cosmic meeting points: Clusters are concentrations of galaxies at the intersection of filaments of cosmic structure • Cosmic Laboratories: Clusters are useful in studying dark matter and the evolution of galaxies Steward Observatory – Gregory Rudnick

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