Title: Unexpected Clustering Pattern and Formation of Dwarf Galaxies

Speaker: Professor Huiyuan Wang (University of Science and Technology of China)

Time: 14:00pm, April 21, 2025

Location: 3-402, PMO Xianlin Campus

Abstract: The galaxy correlation function serves as a fundamental tool for studying cosmology, nature of dark matter  and galaxy formation. It is well established that more massive, redder and more compact galaxies tend to have stronger clustering in space. These results are mainly for normal galaxies and can be understood in terms of galaxy formation in Cold Dark Matter (CDM) halos of different mass and assembly history. Here, we report an unexpectedly strong large-scale clustering for isolated, diffuse and blue dwarf galaxies, comparable to that seen for massive galaxy groups but much stronger than that expected from their halo mass. Our analysis indicates that the strong clustering aligns with the halo assembly bias seen in simulations provided  that more diffuse dwarfs formed in low-mass halos of older ages. This pattern is not reproduced by existing models in the CDM framework that invoke various processes, and our finding provides new clues for the search of a viable solution within the framework. Our results can be explained nicely by assuming self-interacting dark  matter, suggesting that such a scenario should be considered seriously.