Strong conformity and assembly bias: towards a physical understanding of the galaxy-halo connection in SDSS clusters
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY(2022)
摘要
Understanding the physical connection between cluster galaxies and massive haloes is key to mitigating systematic uncertainties in next-generation cluster cosmology. We develop a novel method to infer the level of conformity between the stellar mass of the bright central galaxies (BCGs) M-*(BCG) and the satellite richness lambda, defined as their correlation coefficient rho(cc) at fixed halo mass, using the abundance and weak lensing of SDSS clusters as functions of M-*(BCG) and lambda. We detect a halo mass-dependent conformity as rho(cc) = 0.60 + 0.08ln (M-h/3 x 10(14)h(-1)M(circle dot)). The strong conformity successfully resolves the 'halo mass equality' conundrum discovered in Zu et al. - when split by M-*(BCG) at fixed lambda, the low- and high-M-*(BCG) clusters have the same average halo mass despite having a 0.34-dex discrepancy in average M-*(BCG). On top of the best-fitting conformity model, we develop a cluster assembly bias (AB) prescription calibrated against the CosmicGrowth simulation and build a conformity + AB model for the cluster weak lensing measurements. Our model predicts that with an similar to 20 per cent lower halo concentration c, the low-M-*(BCG) clusters are similar to 10 per cent more biased than the high-M-*(BCG) systems, in good agreement with the observations. We also show that the observed conformity and assembly bias are unlikely due to projection effects. Finally, we build a toy model to argue that while the early-time BCG-halo co-evolution drives the M-*(BCG)-c correlation, the late-time dry merger-induced BCG growth naturally produces the M-*(BCG)-lambda conformity despite the well-known anticorrelation between lambda and c. Our method paves the path towards simultaneously constraining cosmology and cluster formation with future cluster surveys.
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关键词
galaxies: clusters: general, galaxies: evolution, galaxies: formation, galaxies: statistics, cosmology: large, scale structure of Universe
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