CROCODILE-DWARF: Assembly and Kinematics of Field Dwarf Galaxies with GADGET4-OSAKA

Abstract

We present results from CROCODILE-DWARF, a new suite of cosmological zoom-in hydrodynamic simulations of isolated field dwarf galaxies with halo masses of $\sim10^{10}\,M_\odot$ at $z=0$, performed with the GADGET4-OSAKA code. The simulations include detailed modeling of star formation, chemical enrichment, and supernova feedback using the CELib and Grackle libraries, achieving baryonic resolutions of $\sim2\times10^3\,M_\odot$. Our study focuses on how assembly history governs the structural and kinematic diversity of dwarf galaxies within the $Λ$CDM framework. The simulated galaxies reproduce the observed stellar-to-halo mass, mass--metallicity, and size--mass relations for nearby dwarf galaxies, including those of the Local Group, yielding stellar masses of $\sim10^7\,M_\odot$. The galaxies display a broad range of rotational support, where gas is generally more rotationally supported than stars. Differences in morphology and kinematics primarily reflect variations in halo assembly timescales and merger activity. Early-assembling, high-concentration halos form stars efficiently and become gas-poor by $z=0$, while late-assembling, low-concentration halos remain gas-rich due to delayed star formation and rejuvenated gas accretion. We find a trend between rotational support and the cumulative merger mass fraction, providing tentative evidence that dynamical heating induced by mergers plays a role in shaping the kinematic diversity. In some cases, late-time mergers induce the formation of extended gas disks by delivering fresh gas and angular momentum. These results demonstrate that it is assembly history, rather than halo mass alone, that shapes the present-day kinematic and morphological diversity of dwarf galaxies.