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The astrophysics and observational cosmology group is active in a variety of projects involving the study of galaxy clusters, individual galaxies, sheets and voids in the galaxy distribution, and large-scale structure in general. The fundamental links between all these lines of research are that they provide clues to the nature of the dark matter and energy as well as measuring the fundamental parameters of cosmology.

To study these systems, we use a variety of techniques:

•Gravitational Lensing
•X-ray Astrophysics
•Tully-Fisher Studies
•Optical Photometry

In addition, our group is working on problems in galaxy evolution, time-variable astrophysics, and alternate cosmologies.

We also have close links to the other Observational and Experimental Cosmology groups, as well as to the Theoretical Cosmology and High-Energy theory and Experiment groups at Brown.

Observational Cosmology, Gravitational Lensing and Astrophysics Group

This is a deep true color image of the sky taken with the Blanco 4m telescope at the Cerro Tololo Inter-American Observatory in Chile. The image is generated by stacking three images taken through different color filters to create a single color picture. The area covered by this picture is 40 arcminutes by 40 arcminutes, or roughly 1.5 times the size of the full Moon. This picture is of a blank region of the sky; that is, if you looked at this region with your naked eye, you would not see anything. The brightest object in the field (the star at the bottom right) is about 8 times too faint to be seen with the naked eye. The faintest objects detected are almost 100 million times fainter than that! In all, about 150,000 different galaxies are visible in the picture, as well as about 3000 stars.