| A sample of 46 previously unidentified, intermediate- to high-redshift, near-infrared (NIR)-selected galaxy clusters have been discovered in the Andromeda catalog of the Oxford Dartmouth Thirty Degree Survey (ODTS). These clusters vary from low- to high-redshift in distance, 0.1 < z < 0.8, and span galaxy count ranges from poor to rich clusters, richnesses of 10 < NAbell < 100. The clusters were selected from a contiguous field of 1.5 square degrees, imaged in 5 optical passbands, U, B, V, R, i′, and one NIR passband, K. Two algorithms were developed to select the clusters from this multi-color dataset, the ODT Friends (ODTF) and the Brightest-color (BC). The ODTF method adapts the classical friends-of-friends method for use with photometric redshifts. The BC technique takes advantage of previous observations that clusters tend to be dominated by a large early-type galaxy, and that nearly all of the early-type galaxies in the cluster occupy a small space in color-magnitude diagrams. Extensive simulations with artificial galaxies have been performed to test how well these algorithms select clusters as a function of cluster richness and redshift. The ODTF method successfully recovers a larger fraction of the artificial clusters at higher redshift and lower richness class than the BC method, but this method also suffers from a larger number of false cluster identifications than the BC method. After correcting for the selection function and false detection rate of our algorithms, the abundances of ODTS clusters were compared to cluster counts found in other comparable surveys and to the abundance of clusters predicted by models of cluster formation. The ODT cluster number densities are very similar to other comparable surveys. The ODT cluster mass function is consistent with other surveys, and all of these surveys are broadly consistent with a range of cosmological models. |
