SDSS-IV MaNGA: Understanding Ionized Gas Turbulence Using Integral Field Spectroscopy of 4500 Star-forming Disk Galaxies

The Sloan Digital Sky Survey MaNGA program has now obtained integral field spectroscopy for over 10,000 galaxies in the nearby universe. We use the final MaNGA data release DR17 to study the correlation between ionized gas velocity dispersion and galactic star formation rate, finding a tight correlation in which σ _Hα from galactic H II regions increases significantly from ~18-30 km s^-1, broadly in keeping with previous studies. In contrast, σ _Hα from diffuse ionized gas increases more rapidly from 20-60 km s^-1. Using the statistical power of MaNGA, we investigate these correlations in greater detail using multiple emission lines and determine that the observed correlation of σ _Hα with local star formation rate surface density is driven primarily by the global relation of increasing velocity dispersion at higher total star formation rate, as are apparent correlations with stellar mass. Assuming H II region models consistent with our finding that σ _{[O III]} < σ _Hα < σ _{[O I]}, we estimate the velocity dispersion of the molecular gas in which the individual H II regions are embedded, finding values σ _Mol = 5-30 km s^-1 consistent with ALMA observations in a similar mass range. Finally, we use variations in the relation with inclination and disk azimuthal angle to constrain the velocity dispersion ellipsoid of the ionized gas σ _z /σ _r = 0.84 ± 0.03 and σ _ϕ /σ _r = 0.91 ± 0.03, similar to that of young stars in the Galactic disk. Our results are most consistent with the theoretical models in which turbulence in modern galactic disks is driven primarily by star formation feedback.