The Study Of Star Formation Activity In The Brightest Cluster Galaxies From CLASH

Clusters of galaxies are the largest gravitational bound system in the universe, the Brightest Cluster Galaxies(BCGs) in these systems are one of important research objects of galaxy formation and evolution. BCGs are usually quiet elliptical galaxy, they are mostly dominated by old stars, without prominent star formation activity. Early research has shown that low redshift(z < 0.4) BCGs have only a very small proportion(0.5%) with star formation activity. The cold gas which causes these BCGs star formation activity mainly comes from the hot gas cooling in the cluster(cooling). Recently based on the Hubble space telescope(HST) multiband observation CLASH survey, in 23 medium redshift(0.18<z<0.89) clusters, nine BCGs have strong star formation activity(about 40%). The source of cold gas which causes these medium redshift BCGs star formation activity is still not very clear.In order to further determine the source of cold gas which causes these medium redshift BCGs star formation activity, in this paper, to do further research to the property of the CLASH BCGs. Firstly, we compare 23 CLASH on the physical properties of the clusters(stellar mass, entropy, etc.) with BCGs star formation activity. Secondly, based on multi-wavelength, high precision surface photometry process, we further studied the NUV-I color profile of CLASH BCGs under static coordinate system(Rest-frame). By analyzing NUV-I color profile, we further confirm whether these medium redshift BCGs have star formation activity.The main results in this thesis are as follows:(1) the star formation rate of medium redshift BCGs and the quality of host cluster, the entropy of the central region have obvious correlation: the smaller the quality, the lower the entropy and the higher the star formation rate, and no correlation with the physical propertie of BCG itself(such as stellar mass).(2) BCG with star formation activity of NUV-I color gradient is positive(with a blue nuclear). Further confirm nine BCGs have obvious star formation activity in 25 CLASH BCGs(~ 36%).In this thesis, the research results show that the CLASH BCGs do have higher proportion(~ 36%) with star formation activity; Cold gas causes medium redshift BCGs star formation activity that mainly comes from hot gas cooling in the host clusters, rather than the BCG itself. However, since the cold gas mainly comes from the hot gas cooling in the cluster, the other massive galaxy in the central region of cluster will still have a relatively weak star formation activity, we will study the other massive galaxy in the future, in order to further confirm the source of cold gas.