The distribution of neutral hydrogen in the Sombrero galaxy, NGC 4594

The position-velocity contour map presented is based on fan beam observations of NGC 4594 made with the Westerbork Synthesis Radio Telescope in the 21-cm line. A model is proposed which reproduces the gross properties of the H I distribution. The relative H I content is noted to be much lower for this galaxy than for other Sa galaxies, and is lower than for the H I-rich ellipticals; the H I distribution suggests that only gas outside the optical bulge has been able to survive. The gas appears to be confined to an annulus between radii of 12 and 19 kpc, coincident with the distribution of dust in the galaxy.