2024ApJ...966..233E

The correlation between interstellar turbulent speed and local star formation rate surface density, Σ_SFR, is studied using CO observations in the PHANGS survey. The local velocity dispersion of molecular gas, σ, increases with Σ_SFR, but the virial parameter, α_vir, is about constant, suggesting the molecular gas remains self-gravitating. The correlation arises because σ depends on the molecular surface density, Σ_mol, and object cloud mass, M_mol, with the usual molecular cloud correlations, while Σ_SFR increases with both of these quantities because of a nearly constant star formation efficiency for CO. Pressure fluctuations with ΔΣ_SFR are also examined. Azimuthal variations of molecular pressure, ΔP_mol, have a weaker correlation with ΔΣ_SFR than expected from the power-law correlation between the total quantities, suggesting slightly enhanced star formation rate (SFR) efficiency per molecule in spiral arms. Dynamical equilibrium pressure and SFR correlate well for the whole sample, as ${P}_{\mathrm{DE}}\propto {{\rm{\Sigma }}}_{\mathrm{SFR}}^{1.3}$, which is steeper than in other studies. The azimuthal fluctuations, ΔP_DE(ΔΣ_SFR), follow the total correlation P_DE(Σ_SFR) closely, hinting that some of this correlation may be a precursor to star formation, rather than a reaction. Galactic dynamical processes correlate linearly such that ${{\rm{\Sigma }}}_{\mathrm{SFR}}\propto {({{\rm{\Sigma }}}_{\mathrm{gas}}R)}^{1.0\pm 0.3}$ for total gas surface density Σ_gas and galactic dynamical rates, R, equal to κ, A, or Ω, representing epicyclic frequency, shear rate A, and orbit rate Ω. These results suggest important roles for both feedback and galactic dynamics.