Cosmic Large-Scale Structure in the IllustrisTNG Simulations

We have finished two new, extremely large hydrodynamical simulations of galaxy formation that significantly advance the state of the art in cosmology. Together with accompanying dark matter only runs, we call them ‘IllustrisTNG’, the next generation Illustris simulations. Our largest and most ambitious calculation follows a cosmological volume 300 megaparsecs on a side and self-consistently solves the equations of magnetohydrodynamics and self-gravity coupled to the fundamental physical processes driving galaxy formation. We have employed AREPO, a sophisticated moving-mesh code developed by our team over the past 7 years and equipped with an improved, multi-purpose galaxy formation physics model. The simulated universe contains tens of thousands of galaxies encompassing a variety of environments, mass scales and evolutionary stages. The groundbreaking volume of TNG enables us to sample statistically significant sets of rare astrophysical objects like rich galaxy clusters, and to study galaxy formation and the spatial clustering of matter over a very large range of spatial scales. Here we report some early results on the matter and galaxy clustering found in the simulations. The two-point galaxy correlation function of our largest simulation agrees extremely well with the best available observational constraints from the Sloan Digital Sky Survey, both as a function of galaxy stellar mass and color. The predicted impact of baryonic physics on the matter power spectrum is sizeable and needs to be taken into account in precision studies of cosmology. Interestingly, this impact appears to be fairly robust to the details of the modelling of supermassive black holes, provided this reproduces the scaling properties of the intracluster medium of galaxy clusters.