Yikun Wang (CWRU)

Date: Tue. September 8th, 2026, 11:30 am-12:30 pm
Location: Foldy room
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Beyond Halo Mass: Assembly History, Environment, and Baryonic Effects in the Galaxy-Halo Connection

Abstract: Dark matter halos provide the underlying framework for galaxy formation, with halo mass traditionally serving as the primary variable used to connect galaxies with their host halos. However, halos of the same mass can differ in their formation histories, internal structures, and large-scale environments. Consequently, halo clustering depends not only on halo mass but also on secondary halo properties, a phenomenon known as halo assembly bias. Coupled with variations in halo occupation, this underlying effect naturally manifests in the observable universe as galaxy assembly bias.

In this talk, I will use cosmological simulations and controlled, fixed-mass comparisons to investigate what information is carried by halo assembly history, environment, and baryonic processes beyond halo mass. I will present the observable signature of galaxy assembly bias based on different statistics, examine how secondary properties modulate the response of matter distributions to baryonic physics, and test the sensitivity of assembly bias to different underlying dark-matter physics. Finally, I will conclude by outlining how this simulation-based framework can be extended toward an observational test of galaxy assembly bias using Diffsky modeling.