CROCODILE

Welcome to the homepage of CROCODILE simulation project! CROCODILE simulation have been run with the GADGET4-Osaka code (Romano et al. 2022a, 2022b; Oku & Nagamine 2024), a proprietary modified version of the public GADGET-4 code (Springel et al. 2021). GADGET4-Osaka uses TreePM to solve for gravity and the pressure-based entropy-conserving formulation of smoothed particle hydrodynamics (SPH) to solve for hydrodynamics. The SPH implementation includes artificial viscosity using velocity field reconstruction, artificial conduction, and a wake-up timestep limiter to ensure capturing subgrid physics effects in hydrodynamics. The CROCODILE implementation of galaxy formation physics includes radiative cooling and photoionization, star formation, stellar evolution considering a metallicity-dependent stellar initial mass function and hypernova fraction, dust evolution, stellar feedback, and supermassive black hole (SMBH) formation and feedback. Radiative gas cooling is implemented using the Grackle cooling library (Smith et al. 2017) with the ultraviolet background radiation of Haardt & Madau (2012). A non-thermal pressure floor is applied to prevent unphysical fragmentation. Dust production and destruction are modeled on-the-fly with 30 dust-size bins considering the diffusion of dust and metals (Hirashita & Aoyama 2019; Aoyama et al. 2020; Romano et al. 2022a). The stellar feedback includes supernova momentum input and galactic wind, which are modeled based on high-resolution simulations of superbubbles (Oku et al. 2022; Oku & Nagamine 2024), as well as enrichment of 12 metal elements due to type-II and Ia supernovae and AGB stars implemented using the CELib chemical evolution library (Saitoh 2017). The mass, energy, and metal loading factors of the galactic wind are taken from the TIGRESS simulation (Kim et al. 2020). The SMBH growth rate is based on the torque- and Eddington-limited Bondi rate, and the associated AGN feedback is modeled as a stochastic thermal energy dump (Rosas-Guevara et al. 2015; Schaye et al. 2015; Crain et al. 2015) similarly to EAGLE simulations, but with varying parameters. The details of the CROCODILE subgrid model are described in the original paper by Oku & Nagamine (2024), which introduces a simulation set with varying combinations of both SN and AGN feedback.