Too cool for school: eliminating cool-core bias in low-z galaxy cluster statistics with CEREAL

As we push farther out in our observations of galaxy clusters, taking advantage of the discovery capabilities of Sunyaev Zel’dovich surveys like SPT-3G, we are working to understand both the formation of clusters as well as their evolution through cosmic time. However, current population statistics of galaxy clusters at low redshift rely on surveys that are subject to the biases of X-ray archival data-namely cool-core bias and a bias towards interesting systems like mergers. In this work, we present the Cluster Evolutionary Reference Ensemble at Low-z (CEREAL), a mass-selected sample of clusters at z~0.2. We add 47 new Chandra observations to 61 archival observations to produce a statistically complete sample. We examine the dynamical and morphological properties and also begin to analyze the thermodynamic profiles of the CEREAL clusters. We find continuous, unimodal distributions in properties like central entropy and central cooling time as opposed to the bimodal distributions previously observed for other low-redshift samples, confirming our hypothesis that it is critical to avoid the effects of cool core bias if we want to accurately characterize these clusters as a population. The CEREAL sample will serve as an anchor for studies of cluster evolution in the coming years.