Authors: Yun-Hsin Hsu (ASIAA/ NTHU); Yen-Ting Lin (ASIAA); Dylan Nelson (ITA/ZAH); Song Huang(Princeton) and Hsuan-Ting Lai(NCU/ ASIAA)
There is a discrepancy in the stellar mass growth of brightest cluster galaxies (BCGs) at z < 0.5 between model predictions and observations. Solving this discrepancy is not only key in validating the CDM structure formation paradigm, but also central to our understanding of the formation of the most massive galaxies in the universe. The best way to examine this discrepancy is by a direct comparison between models and observations using an observable that can be measured objectively and quantitatively. The multiple-core fraction of BCGs provides such an opportunity for the comparison. We conduct the first IFU survey for the multiple-core fraction of BCGs in the local Universe, utilizing the spatially resolved velocity maps provided by the MaNGA IFU survey, which allow us to robustly distinguish the real associations of the cores with the main body of the BCG from chance projections. With a sample of 89 BCGs, our study represents the statistically meaningful measurement and will serve as a benchmark for model predictions.