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DARK MATTER & GALACTIC ROTATION

2012. ASTRO SUMMER SCHOOL. DARK MATTER & GALACTIC ROTATION. In 1933, Fritz Zwicky calculated the mass of the Coma Cluster. More evidence was discovered by Vera Rubin who measured the rotation curves of many galaxies during the 1970s. The expected distribution of dark matter in the Milky Way.

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DARK MATTER & GALACTIC ROTATION

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  1. 2012 ASTRO SUMMER SCHOOL DARK MATTER & GALACTIC ROTATION

  2. In 1933, Fritz Zwicky calculated the mass of the Coma Cluster

  3. More evidence was discovered by Vera Rubin who measured the rotation curves of many galaxies during the 1970s.

  4. The expected distribution of dark matter in the Milky Way

  5. Cosmic Microwave Background (CMBR)

  6. CMBR Power Spectrum The first peak gives us information about the curvature of the Universe. The ratio of the odd peaks to the even peaks gives us the baryon density. The third peak tells us about the density of dark matter. We can alter the cosmological parameters so that the curve fits the observed data.

  7. This slide will not work correctly without a plugin. Go to: http://map.gsfc.nasa.gov/resources/camb_tool to view the embedded webpage directly.

  8. Dark Matter – Then and Now

  9. Gravitational Lensing

  10. Abell 1689

  11. LRG-3757

  12. The Bullet Cluster

  13. More evidence for dark matter Velocity dispersion of galaxies Measurements of the velocities of galaxies within clusters. Acoustic oscillations Periodic fluctuations in baryonic matter caused by acoustic waves in the early Universe. Type Ia supernovae measurements Put a limit on the amount of dark energy hence constrain dark matter Structure formation If the Big Bang model is correct, dark matter is required to allow structures to form.

  14. Rotation curves A solid body (i.e. a disk) will have a rotational velocity that is proportional to distance – as R increases, v increases. Since , for objects that are gravitationally bound (i.e. not a solid disk), we expect v to be proportional to Galaxies do not follow Keplerian rotation, outside of the core of the galaxy, v is approximately constant. This provides evidence for dark matter.

  15. Galactic rotation curves

  16. Cryogenic detector experiments Cryogenic detectors, operating at temperatures below 100mK, detect the heat produced when a particle hits an atom in a crystal absorber such as germanium. CRESST, Gran Sasso, Italy CDMSII, Soudan Mine, Minnesota

  17. Noble liquid experiments Noble liquid detectors detect the flash of scintillation light produced by a particle collision in liquid xenon or argon. DEAP, Ontario, Canada XENON, Gran Sasso, Italy

  18. Indirect detection methods Indirect detection experiments search for the products of WIMP annihilation. If WIMPs are Majorana particles (the particle and antiparticle are the same) then two WIMPs colliding could annihilate to produce gamma rays or particle-antiparticle pairs. This could produce a significant number of gamma rays, antiprotons or positrons in the galactic halo. The detection of such a signal is not conclusive evidence for dark matter, as the production of gamma rays from other sources are not fully understood. EGRET - Energetic Gamma Ray Experiment Telescope PAMELA - Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics GLAST - Gamma-ray Large Area Space Telescope (also known as Fermi)

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