Tests of the Las Campanas Distant Cluster Survey from Confirmation Observations for the Eso Distant Cluster Survey1

The ESO Distant Cluster Survey (EDisCS) is a photometric and spectroscopic study of the galaxy cluster population at two epochs, z ≃ 0.5 and z ≃ 0.8, drawn from the Las Campanas Distant Cluster Survey (LCDCS). We report results from the initial candidate confirmation stage of the program and use these results to probe the properties of the LCDCS. Of the 30 candidates targeted, we find statistically significant overdensities of red galaxies near 28. Of the ten additional candidates serendipitously observed within the fields of the targeted 30, we detect red galaxy overdensities near six. We test the robustness of the published LCDCS estimated redshifts to misidentification of the brighest cluster galaxy (BCG) in the survey data, and measure the spatial alignment of the published cluster coordinates, the peak red galaxy overdensity, and the brightest cluster galaxy. We conclude that for LCDCS clusters out to z∼ 0.8 , 1) the LCDCS coordinates agree with the centroid of the red galaxy overdensity to within 25(∼ 150h−1 kpc) for 34 out of 37 candidates with 3σ galaxy overdensities, 2) BCGs are typically coincident with the centroid of the red galaxy population to within a projected separation of 200h−1 kpc (32 out of 34 confirmed candidates), 3) the red galaxy population is strongly concentrated, and 4) the misidentification of the BCG in the LCDCS causes a redshift error > 0.1 in 15-20% of the LCDCS candidates. These findings together help explain the success of the surface brightness fluctuations detection method.