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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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Presentation Transcript
slide4
More evidence was discovered by Vera Rubin who measured the rotation curves of many galaxies during the 1970s.
slide7
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.

slide8
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slide14
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.

slide15
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.

slide17
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

slide18
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

slide19
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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