A Spectroscopic and Photometric Survey of Galaxies in Poor Clusters

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Session 30 -- Clusters of Galaxies
Display presentation, Tuesday, 9:30-6:30, Pauley Room

[30.10] A Spectroscopic and Photometric Survey of Galaxies in Poor Clusters

M.V.Newberry, J.Hill (Steward Observatory), R.Price (U. New Mexico)

We have undertaken a program of photometry and spectroscopy of galaxies in "poor" clusters--systems which have too few galaxies to meet the criterion to be Abell "rich" clusters. Poor clusters are important to study since, in the least, they bridge the continuum of environments between those found in groups of a few galaxies and rich clusters. Many, if not all, theories of galaxy formation and evolution are tied in some way to cluster properties. For example, the velocity dispersions of poor clusters are typically 100 to 400 km s$^{-1}$, whereas those of rich clusters are $\sim$ 600 to 2000 km s$^{-1}$. In large part a result of the connection between velocity dispersion, total cluster mass, gas mass, number, and density of galaxies, we suggest that these poor clusters provide an important, previously disregarded niche for testing theories of galaxy formation and evolution.

As a followup to our X-ray survey of poor clusters (Price et al. 1991), we have been acquiring spectroscopy as well as B and R band photometry of galaxies in these clusters in order to determine their luminosity functions and spiral fractions, and to make some assessment of past and present star formation activity as a function of morphological type. We present a progress report on this investigation.

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