Evidence of Halo Assembly Bias in Massive Clusters
  We present significant evidence of halo assembly bias for SDSS redMaPPer
galaxy clusters in the redshift range $[0.1, 0.33]$. By dividing the 8,648
clusters into two subsamples based on the average member galaxy separation from
the cluster center, we first show that the two subsamples have very similar
halo mass of $M_{\rm 200m}\simeq 1.9\times 10^{14}~h^{-1}M_\odot$ based on the
weak lensing signals at small radii $R<\sim 10~h^{-1}{\rm Mpc}$. However, their
halo bias inferred from both the large-scale weak lensing and the projected
auto-correlation functions differs by a factor of $\sim$1.5, which is a
signature of assembly bias. The same bias hypothesis for the two subsamples is
excluded at 2.5$\sigma$ in the weak lensing and 4.4$\sigma$ in the
auto-correlation data, respectively. This result could bring a significant
impact on both galaxy evolution and precision cosmology.
