A flexible modelling of galaxy assembly bias

We use the ILLUSTRIS TNG300 magneto-hydrodynamic simulation, the SAGE semi-analytical model, and the subhalo abundance matching technique (SHAM) to examine the diversity in predictions for galaxy assembly bias (i.e. the difference in the large-scale clustering of galaxies at a fixed halo mass due to correlations with the assembly history and other properties of host haloes). We consider samples of galaxies selected according to their stellar mass or star formation rate at various redshifts. We find that all models predict an assembly bias signal of different magnitude, redshift evolution, and dependence with selection criteria and number density. To model these non-trivial dependences, we propose an extension to the standard SHAM technique so it can include arbitrary amounts of assembly bias. We do this by preferentially selecting subhaloes with the same internal property but different individual large-scale bias. We find that with this model, we can successfully reproduce the galaxy assembly bias signal in either SAGE or the TNG, for all redshifts and galaxy number densities. We anticipate that this model can be used to constrain the level of assembly bias in observations and aid in the creation of more realistic mock galaxy catalogues.

Automated summary

The research team used various simulations and techniques to study the diversity of galaxy assembly bias predictions, finding that all models predict varying levels of assembly bias signal with different magnitudes, redshift evolution, and dependence on selection criteria and number density. They proposed an extension to a standard technique to include arbitrary amounts of assembly bias, which successfully reproduced the observed galaxy assembly bias signal in simulations for all redshifts and galaxy number densities.