Research Interests

Principally, I map the large-scale distribution of matter in the local universe and investigate the interplay between the evolutionary histories of spiral galaxies and their environment. I participated in the early use of the Arecibo (Puerto Rico) telescope for extragalactic atomic hydrogen line spectroscopy and exploited that technique to map the detailed structure and extent of the Pisces-Perseus supercluster. The neutral hydrogen content was used to demonstrate the stripping of interstellar gas by the hot intracluster medium in rich clusters. Even isolated galaxies show evidence for ongoing evolution, such as counter-rotating gas and stellar disks. My recent efforts have exploited a combination of radio and optical datasets to determine distances to galaxies in the local universe by redshift-independent means, thereby allowing measurement of departures from smooth Hubble expansion. Derivation of the peculiar velocity field allows the reconstruction of the underlying density field. These studies have shown that, in the local universe, light does trace mass and that the dipole anisotropy seen in the cosmic microwave background is induced by galaxies within about 6,000 kilometers per second, the local convergence depth.

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Primary Section

Section 12: Astronomy