Phase diagram and limits of resolution. The Jeans instability of the gas above the lines can be calculated properly in SPH simulations. The solid, dashed, dash‐dotted, and dotted lines indicate Jeans mass limits ﹩M_{\mathrm{Jeans}\,}=2N_{\mathrm{nb}\,}M_{\mathrm{SPH}\,}﹩, with mass resolutions of a single SPH particle of ﹩M_{\mathrm{SPH}\,}=10^{3}﹩, 10⁴, 10⁵, and 10⁶ M_⊙, respectively. In the figure, we assume ﹩N_{\mathrm{nb}\,}=50﹩, ﹩\mu =0.59﹩, and ﹩\gamma =5/ 3﹩. The contour map represents the volume‐weighted phase diagram from the numerical simulation of the multiphase ISM in a galaxy (Wada & Tomisaka 2005).