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Date and Time of the Query: 2019-02-18 T10:59:04 PST
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For refcode 2005AJ....129.2597H:
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2005AJ....129.2597H H{alpha} Imaging of Early-Type Sa -- Sab Spiral Galaxies. II. Global Properties Salman Hameed and Nick Devereux Abstract. 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_sun_ yr^-1^, 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 H II regions [L(H{alpha}) >= 10^39^ ergs s^-1^] 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 H II regions in these galaxies. Our results, however, are not in total agreement with the H{alpha} study of Kennicutt & Kent, who did not find any early-type spirals with H{alpha} equivalent widths >14 A. A close examination of the morphological classification of galaxies, however, suggests that systematic differences between the Revised Shapley-Ames Catalog and the Second Reference Catalogue may be responsible for the contrasting results. Keywords: Galaxies: Evolution, Galaxies: ISM, Galaxies: Photometry, Galaxies: Spiral, ISM: H II Regions
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