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The Ohio State University
College of Mathematical & Physical Sciences
Department of Astronomy Colloquium Series 2006/7
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Thursday, November 16, 3:30 p.m.
2015 McPherson Laboratory
A direct empirical proof of the existence of
dark matter
Prof. Douglas Clowe
Dept. of Physics & Astronomy, Ohio University
Since Zwicky in 1933, we have known that clusters of galaxies
have gravitational potentials that are too large to be explained by the
amount of visible baryons under the assumption of a Newtonian
gravitational force law. This has led to competing theories that either
the masses of clusters are dominated by a non-baryonic form of matter or
that gravity departs from an inverse-square force law on cluster scales.
By using merging clusters of galaxies, I will show that the different types of
matter in the clusters can be spatially seperated and by using
gravitational lensing I will prove, independent of any assumptions about
the nature of the law of gravity, that the dominant mass component of the
clusters is not the visible baryons. I will also discuss how these
observations can be used to place constraints on the nature of the dark
matter, including a limitation on the self-interaction cross-section of
any dark matter particles, as well as constraints on the gravitational
force law.
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