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

Abstract: We present results from CROCODILE-DWARF, a 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 \textsc{gadget4-osaka} code. The simulations include detailed modeling of star formation, chemical enrichment, and supernova feedback using the \textsc{CELib} and \textsc{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 $\Lambda$CDM framework. The simulated galaxies reproduce the observed stellar-to-halo mass, mass--metallicity, and size--mass relations, yielding stellar masses of $10^6-10^8\,M_\odot$ and metallicities consistent with those of Local Group dwarf galaxies. 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 identify a clear anti-correlation between rotational support and the cumulative merger mass fraction, demonstrating that dynamical heating by mergers is the dominant factor shaping 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 assembly history, rather than halo mass alone, critically shapes the present-day kinematic and morphological diversity of dwarf galaxies.