An Hα atlas of nearby southern spiral galaxies

Abstract

We present here an atlas of CCD images of 25 nearby southern spiral galaxies taken through narrow-band (15 Å) Hα filters, and accompanying red continuum (6676 Å) images. Most of these galaxies have never previously been imaged in Ha and will complement the earlier photographic atlas of Hodge & Kennicutt. We comment on the individual distributions of the H II regions in relation to the morphology and characteristics of each galaxy. Nearly half of the galaxies surveyed exhibit rather asymmetrical distributions of star formation activity, even though the stellar distributions may be quite regular. Among galaxies possessing both a strong stellar bar and an encircling inner ring, there appears to be a decrease in the number of H II regions tracing out the bar as the number of H II regions in the ring itself increases, and vice versa. The images should prove useful mainly as finding charts for in-depth studies of the H II region populations, as well as for the purposes of determining abundance gradients and the kinematics of these galaxies. Show more