HI velocity dispersion in NGC 1058

We present excellent-resolution and high-sensitivity Very Large Array observations of the 21 cm H I line emission from the face-on galaxy NGC 1058, providing the first reliable study of the H I profile shapes throughout the entire disk of an external galaxy. Our observations show an intriguing picture of the interstellar medium; throughout this galaxy velocity dispersions range between 4 and 15 km s(-1) but are not correlated with star formation, stars, or the gaseous spiral arms. The velocity dispersions decrease with radius, but this global trend has a large scatter as there are several isolated, resolved regions of high dispersion. The decline of starlight with radius is much steeper than that of the velocity dispersions or that of the energy in the gas motions.