Major Dry-Merger Rate and Extremely Massive Dry-Mergers of BCGs

Abstract

Possible ongoing dry merger pairs of the early type Brightest Cluster Galaxies (BCGs) have been searched from a sample of 515 BCGs with redshifts between 0.03 to 0.12 selected from the C4 cluster catalogue. The results are compared with those of GEMS (Galaxy Evolution from Morphology and SEDs Survey) [1]. We find that BCGs have much higher ongoing merger fraction than that of luminous early‐type galaxies from GEMS. This may infer that BCGs have higher dry‐merger rate. We also found the trendence that the BCGs in richer clusters tend to have higher merger fraction than that in poorer clusters. With careful inspection, we find that extremely massive major dry mergers do exist in the BCGs sample which shows that they are not rare locally and may have important implication on the evolution of BCGs.