HI Distribution and Kinematics in the Peculiar Spiral Galaxy NGC 5474

November 1994 • 1994AJ....108.1638R

Authors • Rownd, B. K. • Dickey, J. M. • Helou, G.

Abstract • We present a detailed study of the distribution and kinematics of neutral hydrogen in the peculiar small spiral galaxy NGC 5474. Our VLA D-array observations show that its extended H I disk has a clumpy structure. The H I velocity field indicates that the galaxy `s gas disk is in normal differential rotation, with a pronounced warp developing beyond the bright optical disk. We confirm the observation of van der Hulst & Huchtmeier [A&A,78,82 (1979)] that the optical feature resembling a nuclear bulge is offset from the kinematic center of the galaxy. NGC 5474's very low inclination allows us to study the z motions of its H I disk. With our 5.2 km s' spectral resolution we find the z velocity distribution to be adequately represented by a single Gaussian component. Thus, there is no detectable population of high velocity clouds, nor is there any ordered pattern of velocity residuals about the best fit differential rotation model. Our interpretation is that the gravitational field of nearby M101 strips off the fountain gas before it has time to recombine and fall back toward NGC 5474. Thus, the bridge between M 101 and NGC 5474 is in part populated by the missing high- and intermediate- velocity clouds of NGC 5474.

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