H-alpha Imaging of Early-type (Sa-Sab) Spiral Galaxies II. Global   Properties
  New results, based on one of the most comprehensive H-alpha imaging surveys of nearby Sa-Sab spirals completed to date, reveals early-type spirals to be a diverse group of galaxies that span a wide range in massive star formation rates. While the majority of Sa-Sab galaxies in our sample are forming stars at a modest rate, a significant fraction (~29%) exhibit star formation rates greater than 1 M(solar/yr), rivaling the most prolifically star forming late-type spirals. A similar diversity is apparent in the star formation history of Sa-Sab spirals as measured by their H-alpha equivalent widths. Consistent with our preliminary results presented in the first paper in this series, we find giant HII regions (L(H-alpha)>10^{39}erg/s) in the disks of 37% of early-type spirals. We suspect that recent minor mergers or past interactions are responsible for the elevated levels of H-alpha emission and perhaps, for the presence of giant HII regions in these galaxies. 
Salman Hameed (Smith College/Five College Astronomy Department) and   Nick Devereux (Embry-Riddle Aeronautical University)