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A.0. Petric (NMIMT), M.P. Rupen (NRAO)
We use HI observations to trace the vertical motions of the neutral gas in the face-on spiral galaxy NGC 1058. The combination of high sensitivity and low inclination permits the accurate measurement of line profiles at high spatial and spectral resolution, virtually uncontaminated by planar motions associated with disk rotation or spiral density waves. Although the width of the line profile varies from one beam to the next (FWHM= 14 -- 30 km/s), some global trends are evident. The lines are broader in the central 1.5arcmin, where the star formation is most vigorous. However, outside this region the linewidths are uniformly smaller in the spiral arms than in the interarm regions; and there is a general anticorrelation between H\alpha emission and broad profiles. The line profiles are not Gaussian, and hence cannot solely be determined by single-temperature thermal broadening. The surprise is that the observed shape does seem to be universal, in the sense that the line profiles at every pixel, when scaled by their FWHMs, appear identical. This implies that whatever mechanism determines the relative distribution of kinetic energies operates in the same fashion throughout the galaxy -- both within and beyond the stellar disk, in quiescent regions and in regions with active star formation.