Clusters of galaxies

Clusters of galaxies are the largest bound systems in the Universe. They are located at the knots of the cosmic web and therefore are important tracers of the large-scale structure of the Universe. They provide various environments for galaxies and affect their evolution. They are formed by merging process, hence have diverse states of dynamics shown in optical and X-ray images.

In early days, galaxy clusters were identified from optical surveys, as the most famous cluster catalog obtained by Abell and his successors. Recently, data of many large sky area surveys are available, such as the Sloan Digital Sky Survey (SDSS), SuperCOSMOS, the Wide-field Infrared Survey Explorer (WISE) and unWise, and the Hyper Suprime-Cam Subaru strategic program (HSC-SSP). From these survey data, we have identified a great number of clusters of galaxies: See here:

Many catalogs of clusters of galaxies we obtained!

Based on these large samples of clusters and public data, we studied the properties of clusters, including dynamical states of clusters, radio emission from clusters, the constraints of cosmological parameters, and discovery of giant lensed arcs by clusters. See many details here!

Recently a new method to determine the dynamical states of clusters of galaxies has been developed, and compared with the previous results for 964 X-ray clusters observed by the Chandra observatory.