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Using numerical simulations of galactic disks resolving scales from ~1 toseveral hundred pc, we investigate dynamical properties of the multiphase ISMwith turbulence driven by star formation feedback. We focus on HII regioneffects by applying intense heating in dense, self-gravitating regions. Ourmodels are two-dimensional radial-vertical slices through the disk, and includesheared background rotation, vertical stratification, heating and cooling toyield temperatures T~10-10^4K, and thermal conduction. We separately vary thegas surface density Sigma, the stellar volume density rho_*, and the localangular rotation rate Omega to explore environmental dependencies, and analyzethe steady-state properties of each model. Among other statistics, we evaluateturbulent amplitudes, virial ratios, Toomre Q parameters including turbulence,and the mass fractions at different densities. We find that the dense gas(n>100 cm^-3) has turbulence levels similar to observed GMCs and virial ratios~1-2. The Toomre Q parameter in dense gas reaches near unity, demonstratingself-regulation via turbulent feedback. We also test how the star formationrate Sigma_SFR depends on Sigma, rho_*, and Omega. Under the assumption thatthe star formation rate is proportional to the mass at densities above n_thdivided by the free-fall time at that threshold, we find that Sigma_SFR variesas Sigma^(1+p) with 1+p ~ 1.2-1.4 when n_th=10^2 or 10^3 cm^-3, consistent withobservations. Estimated star formation rates based on large-scale properties(the orbital time, the Jeans time, or the free-fall time at thevertically-averaged density) however depart from rates computed using the densegas mass, indicating that resolving the ISM structure in galactic disks atscales <<H is necessary for accurate predictions of the star formation rate.

Gas Properties and Implications for Galactic Star Formation in Numerical Models of the Turbulent, Multiphase ISM