The distribution of atomic gas and dust in nearby galaxies - III. Radial distributions and metallicity gradients

The radial distribution of dust and gas in 38 nearby galaxies is investigated, using a sample of galaxies for which matched resolution (25 arcsec) neutral hydrogen (H i) and 850-μm images are available. Most of these radial profiles are fitted well by an exponential model, and the derived 850-μm scalelengths are proportional to the H i scalelengths. From this relation, it is found that the metallicity gradients of these galaxies are much shallower than previous studies, unless the dust temperature is constant within the disc, or a significant component of molecular gas exists at large radii that is not traced by CO observations