The SEEDZ Simulations: Methodology and First Results on Massive Black Hole Seeding and Early Galaxy Growth

Here we introduce the SEEDZ simulations, a large suite of cosmological hydrodynamic simulations exploring the formation and growth of the first black holes in the Universe, that may form through ‘light’ or ‘heavy’ seeding channels. Specifically, SEEDZ includes models for Population III star formation, supernova explosions and the resulting formation of ‘light’ seed black holes. It also incorporates a model for subsequent metal enrichment, Population II star formation, ‘heavy’ seed black hole formation, (super-)Eddington accretion as well as black hole feedback. In this paper, we cover the overall methodology employed and present our current results up to z = 15. We find that black holes initially grow faster than their host galaxies, resulting in over-massive black holes with respect to the local black hole-galaxy scaling relations, when grown from seeds with ∼10 4 M ⊙. At the high-end of our black hole masses, our simulated galaxy M BH-M ∗ relations match the observed high-redshift trends, i.e. over-massive black holes with M BH/M star ∼ 10 −2. Hence, our simulations suggest that the fundamental black hole-galaxy relationships we observe at z = 0, especially the M BH-M ∗ relationship, likely only emerge in more mature galaxies. This initial set of simulations will be performed down to z = 10, where we will conduct a comprehensive comparison of simulated black hole number densities and scaling relations with JWST observations. Further simulations with higher resolution will then follow.