Metallicity Dependence of Pressure-Regulated Feedback-Modulated Star Formation in the TIGRESS-NCR Simulation Suite

We present a new suite of numerical simulations of the star-forming interstellar medium (ISM) using the TIGRESS-NCR framework, covering a wide range of galactic conditions including metallicity. The TIGRESS-NCR framework is a model of the ISM in galactic disks that solves ideal MHD equations with self-gravity in a local shearing-box, including explicit treatment of cooling and heating processes coupled with ray-tracing UV radiation transfer and resolved supernova feedback. The TIGRESS-NCR suite presented in this paper covers metallicity variation Z'≡ Z/Z_~ 0.1-3, gas surface density Σgas~5-150\,M_ pc⁻², and stellar surface density Σₛₜₐᵣ~1-50M_ pc⁻², leading to emergent SFR surface density ΣSFR~ 10⁻⁴-0.5M_ kpc⁻²yr⁻¹ and ISM total midplane pressure Pₜₒₜ/kB=10³-10⁶ cm⁻³K, with Pₜₒₜ equal to the ISM weight W. In our simulation suite, ΣSFR ∝ Z'0.3, which can be understood based on feedback physics. We present a new calibration for the components of feedback yield Υ, defined as ratios between pressure (thermal, turbulent, and magnetic) and ΣSFR. We find that the thermal feedback yield varies sensitively as Υₜₕ∝ W-0.46Z'-0.53, while the combined turbulent and magnetic feedback yield shows weaker dependence Υturb+mag∝ W-0.22Z'-0.18. The reduced ΣSFR at low metallicity is due mainly to enhanced thermal feedback yield resulting from reduced attenuation of UV radiation. Combining vertical dynamical equilibrium, feedback yield, and effective equation of state, we provide a new metallicity-dependent subgrid star formation prescription that can be used in cosmological simulations where the ISM is unresolved.