Morphological classification of the OSU Bright Spiral Galaxy Survey

Abstract

To quantify the distribution of bar shapes in spiral galaxies, we have analysed 113 H-band and 89 B-band galaxy images from the Ohio State University Bright Spiral Galaxy Survey. Parameters measuring bar shape and position along the Hubble sequence were obtained in each waveband. Evidence was found for a bimodality in the distribution of bar shape, implying that barred and unbarred galaxies are not just the extrema of a single distribution, and that any evolution between these two states must occur on a rapid time-scale. Objective bar shapes measured in the H-band were found to be more closely related to visual classifications than B-band bar strengths, as the B-band images are somewhat compromised by localized star formation, especially in later type systems. Galaxies were found to be more centrally concentrated in the infrared. Later type galaxies showed greater asymmetry in the optical than the infrared, presumably again owing to localized star formation, but on average the bar shapes in the two bands were found to be the same.