Merger Rate of MaNGA Brightest Cluster Galaxies

Yun-Hsin Hsu^1,2*, Yen-Ting Lin¹, Dylan Nelson³

¹Institute of Astronomy and Astrophysics, Academia Sinica, Taipei, Taiwan
²Institute of Astronomy, National Tsing Hua University, Hsinchu, Taiwan
³Max-Planck-Institut für Astrophysik, Garching, Germany

* Presenter:Yun-Hsin Hsu, email:yuhhsu@asiaa.sinica.edu.tw

Numerical simulations of ΛCDM suggest that typical central galaxies in massive dark matter halos, also known as the brightest cluster galaxies (BCGs), have undergone many merging events at redshift z<1. Observationally verifying such a prediction is not only key in validating the ΛCDM structure formation paradigm, but also central to our understanding of the formation of the most massive galaxies in the universe.
In order to derive the merger rate of BCGs, we combine the measurement of the frequency of BCGs with multiple cores (indicative of a merger in progress), and the merger timescale from the state-of-the-art cosmological hydrodynamical simulations. Our BCG sample is extracted from the MaNGA survey, which provides spatially resolved velocity information for each of our BCGs, and allows us to robustly distinguish real associations of the cores with the main body of the BCG from chance projections. The merger time scale is derived from the 300 Mpc box of illustrisTNG. We trace the merging events of BCGs in the simulation, and the time it appears as multiple-core that satisfies our observational criteria. Combined together, we present the most robust measurements of the BCG merger rates to date.

Keywords: galaxy formation, galaxy clusters, elliptical and lenticular, cD galaxies, photometry