Dark matter galactic rotation
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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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DARK MATTER & GALACTIC ROTATION

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Dark matter galactic rotation

2012

ASTRO SUMMER SCHOOL

DARK MATTER & GALACTIC ROTATION


Dark matter galactic rotation

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


Dark matter galactic rotation

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


Dark matter galactic rotation

The expected distribution of dark matter in the Milky Way


Dark matter galactic rotation

Cosmic Microwave Background (CMBR)


Dark matter galactic rotation

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.


Dark matter galactic rotation

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Dark matter galactic rotation

Dark Matter – Then and Now


Dark matter galactic rotation

Gravitational Lensing


Dark matter galactic rotation

Abell 1689


Dark matter galactic rotation

LRG-3757


Dark matter galactic rotation

The Bullet Cluster


Dark matter galactic rotation

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.


Dark matter galactic rotation

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.


Dark matter galactic rotation

Galactic rotation curves


Dark matter galactic rotation

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


Dark matter galactic rotation

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


Dark matter galactic rotation

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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