Correlation between baryonic process and galaxy assembly bias

Abstract

Galaxy assembly bias (GAB) is the dependence of galaxy clustering on secondary properties beyond halo mass. In this work, we study the connections between GAB and baryonic processes using the Galacticus semi-analytic model (SAM) for galaxy formation and evolution applied to the UNIT simulation. By generating hundreds of galaxy mocks with varying parameters governing gas cooling, star formation, stellar feedback, and AGN feedback, we employ a shuffling method to quantify the GAB signal and compare the contributions of halo concentration and local environment to GAB. Using the Random Forest algorithm, we evaluate the importance of different baryonic processes for GAB. We find that for stellar-mass-selected galaxies, the dominant baryonic processes are gas cooling and stellar feedback, and the result does not change significantly with the number density; for SFR-selected galaxies, the primary process shifts from star formation to gas cooling as the number density increases. These results establish a direct and quantitative link between baryonic physics and GAB, which can provide guidance for empirical GAB parameterizations in upcoming and future galaxy surveys.