Dynamical state estimators. Left and middle panels: comparison between the three estimators defined in Wen & Han (2013). Three different richness bins are color-coded. Right: distance to the next neighbor found in the galaxy density map vs. distance to the next neighbor in the X-ray cluster catalog. The one-to-one relation is indicated as a red line. Clusters showing a near neighbor within ~2.5 * r₅₀₀ in both X-ray and optical are likely cluster pairs that potentially are merging.