GLOBAL H i KINEMATICS IN DWARF GALAXIES

H i line widths are typically interpreted as a measure of interstellar medium turbulence, which is potentially driven by star formation (SF). In an effort to better understand the possible connections between line widths and SF, we have characterized H i kinematics in a sample of nearby dwarf galaxies by co-adding line-of-sight spectra after removing the rotational velocity to produce average global H i line profiles. These “superprofiles” are composed of a central narrow peak (∼6–10 km s−1) with higher-velocity wings to either side that contain ∼10%–15% of the total flux. The superprofiles are all very similar, indicating a universal global H i profile for dwarf galaxies. We compare characteristics of the superprofiles to various galaxy properties, such as mass and measures of SF, with the assumption that the superprofile represents a turbulent peak with energetic wings to either side. We use these quantities to derive average scale heights for the sample galaxies. When comparing to physical properties, we find that the velocity dispersion of the central peak is correlated with 〈ΣH i〉. The fraction of mass and characteristic velocity of the high-velocity wings are correlated with measures of SF, consistent with the picture that SF drives surrounding H i to higher velocities. While gravitational instabilities provide too little energy, the SF in the sample galaxies does provide enough energy through supernovae, with realistic estimates of the coupling efficiency, to produce the observed superprofiles.