Speaker
Description
Assembly bias, which is variations in clustering at fixed halo mass due to differences in halo formation history, is challenging to detect observationally. We investigate a stellar mass–dependent assembly bias using a large sample of massive galaxy clusters with spectroscopically confirmed brightest cluster galaxies (BCGs). Combining galaxy–galaxy lensing and projected correlation function measurements, we constrain their relative halo bias. We find that high-stellar-mass centrals reside in more concentrated halos but are less clustered on large scales, with a bias ratio significant at over $5\sigma$. These results are independently confirmed with the Flamingo and MillenniumTNG hydrodynamical simulation in our work, which reproduces the observed assembly bias on stellar mass.
