Galaxy-Halo Connection
Galaxies are born and raised in dark matter halos, so they are tightly related to each other. Previous research has established the primary galaxy-halo connection, which is known as the stellar mass-halo mass relation (SHMR), from which we infer the necessity of supernovae feedback and AGN feedback to suppress the conversion from baryon to stars in low-mass and high-mass halos, respectively. Nowadays, people start to pursue the secondary galaxy-halo connection, and I am one of them. The ultimate question in this regard is that
Dark Matter Halo
Dark matter halos are the building blocks of our Universe, and they can be characterized from three perspectives: The temporal dimension: the assembly of dark matter halos as a function of cosmic time, which can be described by halo merger trees. The intra-halo dimension: the spatial and kinematic structures of dark matter halos, such as halo density profile, halo shape, halo spin, and substructures. The inter-halo dimension: the spatial clustering of dark matter halos.
Connect Structures across Cosmic Time
Galaxies at different redshifts are causally irrelevant but can be statistically linked together. Our strategy is to build the connection between galaxies and cosmic structures, such as dark matter halos and protoclusters, at different redshifts, and connect these structures across cosmic time using cosmological N-body simulations, which is more reliable and convergent than hydrodynamical galaxy formation simulations.
Galaxy formation models
Galaxy surveys during last decades have provided us with numerous observational data, and more to expect from upcoming surveys. Meanwhile, modern numerical simulations of galaxy formation have greatly deepened our understanding of many fundamental astrophysical processes. However, the observation has not reached the physics yet, nor vice versa. There is a huge gap between them: we cannot accurately probe many crucial components, like dark matter halos, multi-phase gas, and super-massive black holes, of galaxies in observation, nor do we have the ability to accurately model the complex astrophysical processes, like stellar feedback, AGN feedback and the growth of super-massive black hole, in hydrodynamical galaxy formation simulations. To bridge this gap, we propose to build a semi-analytical galaxy formation model that is motivated by various astrophysical processes in hydrodynamical simulations and calibrated to reproduce the statistical behavior of observed galaxies. There are a lot of questions to be answered by this model, and currently I am focusing on the following ones: