AAS 195th Meeting, January 2000
Session 31. Star Formation in Nearby Spirals: Environment and Tracers
Oral, Wednesday, January 12, 2000, 2:00-3:30pm, Centennial IV

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[31.03] Massive Star Formation in Early-type(Sa-Sab) Spiral Galaxies

S. Hameed (New Mexico State University)

We have conducted an H\alpha imaging survey of 57 bright, nearby, early-type spiral galaxies. The new H\alpha images have revealed them to be a heterogeneous class of galaxies with H\alpha morphologies ranging from filamentary, low luminosity nuclear emission line spirals to what we suspect are compact, luminous nuclear starbursts. Contrary to popular perception, our images have revealed a significant number(15-20%) of Sa-Sab galaxies with massive star formation rates comparable to the most prolifically star forming Sc galaxies.

A determination of the H\alpha morphology and a measure of the H\alpha luminosity suggests that early-type spirals can be classified into two broad categories. The first category includes galaxies for which the individual HII regions have L(H\alpha) < 1039 erg/s. Most of the category 1 galaxies appear to be morphologically undisturbed, but show a wide diversity in nuclear H\alpha properties. The second category includes galaxies which have at least one HII region in the disk with L(H\alpha) \ge 1039 erg/s. All category 2 galaxies show morphological peculiarities, such as tidal tails, which suggests that the anomalously luminous HII regions may have formed as a result of a recent interaction. We have also determined HII region luminosity functions for a subset of our sample and find that the shape of the HII region LF is different when a giant HII region is present compared to a galaxy which contains only HII regions of modest luminosity. The difference may point to corresponding differences in massive star formation triggering mechanisms.

If you would like more information about this abstract, please follow the link to http://astro.nmsu.edu/~shameed/research.html. This link was provided by the author. When you follow it, you will leave the Web site for this meeting; to return, you should use the Back comand on your browser.

The author(s) of this abstract have provided an email address for comments about the abstract: shameed@nmsu.edu

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