The ASTRID Simulation at z = 0: From Massive Black Holes to Large-scale Structure

Abstract We present the z = 0 results for the cosmological simulation ASTRID . Hosting 2 × 5500 3 ≈ 0.33 trillion particles in a box of 370 Mpc per side, ASTRID is one of the largest cosmological hydrodynamic simulations evolved to z = 0. ASTRID features a large population of massive black holes (MBHs), covering a wide mass range 4 × 10 4 ∼ 2 × 10 11 M ⊙ . The adopted dynamical friction model provides a relatively accurate description of MBH dynamics, making ASTRID a powerful tool to study MBH growth and mergers in a cosmological context. ASTRID successfully captures the coevolution of MBHs and their host galaxies, producing M BH – M ⋆ and M BH – σ relations in good agreement with observations. Notably, ASTRID generates scatter in these relations that is more consistent with observations than previous simulations, indicating a more realistic MBH diversity. The galaxy stellar mass function at z = 0 is generally consistent with observational constraints. When dust attenuation is applied, the galaxy luminosity function also agrees well with observations, and the bimodality in galaxy colors is reproduced as well. ASTRID hosts a large population of massive galaxy groups and clusters: seven halos have M 200c > 10 15 M ⊙ , and 9709 halos have M 200c > 10 13 M ⊙ . We quantify the stellar mass content in these halos, and find that the correlations between the stellar and halo mass match well with observational constraints. Finally, we present the z = 0 power spectra of MBH and galaxies, as well as their bias with respect to the matter power spectrum. We find that MBHs with M BH ≥ 10 8 M ⊙ and galaxies with M ⋆ ≥ 10 10.5 M ⊙ serve as good tracers of large-scale structure.