Research Interests

The major portion of my research has concerned the masses of galaxies and clusters of galaxies and the distribution of matter -- dark and luminous -- within them. For the past decade I have been studying the gravitational mirages produced by galaxies and clusters of galaxies using ground-based telescopes and the Hubble Space Telescope. These mirages permit the mapping of matter even when it is invisible. Early on in my career Bill Press and I developed a simple model for the formation of clusters of galaxies that, despite gross simplifications, seems to reproduce the observed distribution of cluster masses and its evolution with time. Somewhat mysteriously, the functional form predicted for the distribution of cluster masses also gives an excellent empirical fit to the distribution of galaxy luminosities. In the past few years an appreciable fraction of my time has been devoted to measuring the wavefront errors in the images delivered to the focal plane of the Magellan telescopes in Chile. The error signals are used to keep the primary mirrors strictly parabolic and to keep the secondary mirrors in position, and will soon be used to compensate for the corruption of images by the Earth's atmosphere.

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Section 12: Astronomy