Collaborative Project: Astrophysics of Early-Type Dwarf Galaxies

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AST 98-0473018 John S. Gallagher Dr. Gallagher and Dr. Wyse are collaborating to study the properties of the stellar populations in faint dwarf galaxies. These galaxies belong to the type of galaxy that contains the most members. A range of quantitative measurements with new generations of instruments, at observatories on the ground and in space, now show that even when restricted to the superficially similar gas poor dwarf elliptical systems, dwarf galaxies have diverse morphologies and star formation histories. Why these dwarfs are so varied is not known. Does this reflect initial conditions, environmental influences, or both? Extant data suggest that dwarf ellipticals prefer dense environments - is this invariably true? What are the effect on the dwarfs, and the implications for disentangling "nature vs. nurture"? Further, the internal dynamics of dwarf spheroidal galaxies, measured from stellar velocities, leads to an inferred dark matter content easily surpassing, in relative terms, that of high surface brightness giant galaxies. The implications of dense dark matter in tiny galaxies are unclear. Does this mean different types of dark matter in different classes of galaxies? If so, which dwarf galaxies, if any, are representative of the building blocks of giant galaxies? The research team is investigating these questions through new observations and modeling of gas poor dwarf galaxies. They use the new technology ARC telescope (consortium through Johns Hopkins University) and the WIYN 3.5m telescope (consortium through the University of Wisconsin) to obtain spectra and photometry of dwarf galaxies in three clusters of galaxies: the Virgo cluster, the Coma cluster and the Perseus cluster. ***