Spiral Arm Properties

(1) Three basic arm categories in the Elmergreen classification scheme: Grand Design; Multiarm (intermediate); Flocculent.
(2) Arm/Interarm contrasts (A = 0.4 x 10^m), where m is the magnitude difference, for B (top) and I (bottom) colors.

(3) A plot of the ratio of arm contrasts in B and I versus the arm contrast in I. This separates the different arm classes of galaxy quite well. Figures taken from Debora Elmergreen's book : Galaxies and Galactic Structure.

(1) Three basic arm categories in the Elmergreen classification scheme: Grand Design; Multiarm (intermediate); Flocculent.	(2) Arm/Interarm contrasts (A = 0.4 x 10^m), where m is the magnitude difference, for B (top) and I (bottom) colors.
(3) A plot of the ratio of arm contrasts in B and I versus the arm contrast in I. This separates the different arm classes of galaxy quite well.	Figures taken from Debora Elmergreen's book : Galaxies and Galactic Structure.