The Stanford Cluster Search: Scope, method, and preliminary results

We describe the scientific motivation behind, and the methodology of, the S tanford Cluster Search (StaCS), a program to compile a catalog of optically selected galaxy clusters at intermediate and high (0.3 less than or simila r to z less than or similar to 1) redshifts. The clusters are identified us ing a matched filter algorithm applied to deep CCD images covering similar to 60 deg(2) of sky. These images are obtained from several data archives, principally that of the Berkeley Supernova Cosmology Project of Perlmutter et al. Potential clusters are confirmed with spectroscopic observations at the 9.2 m Hobby-Eberly Telescope. Follow-up observations at optical, submil limeter, and X-ray wavelengths are planned in order to estimate cluster mas ses. Our long-term scientific goal is to measure the cluster number density as a function of mass and redshift, n(M, z), which is sensitive to the cos mological density parameter Omega (m) and the amplitude of density fluctuat ions sigma (8). The combined data set will contain clusters ranging over an order of magnitude in mass and allow constraints on these parameters accur ate to similar to 10%. We present our first spectroscopically confirmed clu ster candidates and describe how to access them electronically.