groups of galaxies in the study of galaxy properties as a function of environment. In particular, I discuss the “SFR–Density” and “Morphology–Radius” relations for the SDSS and note that both of these relationships have a [*critical density*]{} (or “break”) at a projected local galaxy density of $\simeq 1\,h_{75}^2\,{\rm Mpc^{-2}}$ (or between $1$ to $2$ virial radii). One possible physical mechanism to explain this observed critical density is the stripping of warm gas from the halos of in–falling spiral galaxies, thus leading to a slow strangulation of star–formation in these galaxies. This scenario is consistent with the recent discovery (within the SDSS) of an excess of “Passive” or “Anemic” spiral galaxies located within the in–fall regions of C4 clusters.
author:
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    R. C. Nichol\
    Dept. of Physics, Carnegie Mellon University
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\[1996/06/01\]

å[[A&A]{}]{}

Clusters of Galaxies in the SDSS
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Introduction
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As demonstrated by this conference – [*Clusters of Galaxies: Probes of Cosmological Structure and Galaxy Evolution*]{} –, clusters and groups of galaxies have a long history as key tracers of the large–scale structure in the Universe and as laboratories within which to study the physics of galaxy evolution. At the conference, their important role as cosmological probes was 