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Galaxy Clusters and Cosmology

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MACS0025 in visible light and X-rays. Overlaid on the HST image are X-rays in violet (showing the location of the normal matter), and dark matter in blue (from gravitational lensing).

Our work uses the observed distribution and internal properties of clusters, as functions of mass and redshift, to probe the natures of dark matter, the weakly interacting yet dominant matter component of the Universe, and dark energy, which drives cosmic acceleration. Measurements of galaxy clusters are powerful tools for such work, alongside measurements of the cosmic microwave background, supernovae and galaxy surveys.

X-ray observations allow us to determine the distribution of matter within galaxy clusters, both the baryonic mass (predominately hot gas) and non-baryonic dark matter. Another way to measure cluster masses utilizes gravitational lensing, the bending of light rays caused by massive objects, as predicted by General Relativity. Our group has been at the forefront of using gravitational lensing measurements of clusters to help constrain the properties of dark matter and obtain improved constraints on cosmological models. 

For further discussion of this work, see e.g.: