Distribution of Star-Forming Sites in Barred Spiral Galaxies
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Session 23 -- Galaxies I
Oral presentation, Wednesday, January 12, 10:15-11:45, Salon IV Room (Crystal Gateway)

[23.06] Distribution of Star-Forming Sites in Barred Spiral Galaxies

A. C. Phillips (Lick Observatory)

\def\Halpha{{H$\alpha$}} \def\HIIR{{{\sc H\thinspace ii} region}} \def\micron{{\rm $\mu$m}}

Narrow-band \Halpha\ images of 15 SBb and SBc galaxies have been used to survey star formation properties of barred spiral galaxies. Integrated \Halpha\ luminosities and surface brightness measures, as well as the spatial and luminosity distribution of \HIIR s, are determined. Here we present the results concerning the distribution of star-forming sites in these galaxies.

Barred spirals display a wide range in their star formation properties. Within the sample, properties tend to fall into two categories, which roughly correlate with Hubble type. SBb galaxies show moderate to virtually no (massive) star formation in their bars, except in the circumnuclear regions where star formation rates (SFRs) can be extreme. Outside the bar, \HIIR s appear concentrated in ring-like structures corresponding to the inner rings of ring galaxies. SBc galaxies generally have luminous \HIIR s in their bars, lack circumnuclear starbursts, and inner rings are much less pronounced. These differences also correlate with the ``flat'' and ``exponential'' bar types defined by Elmegreen \& Elmegreen (1985). SFRs per unit area are generally enhanced where the bar joins the spiral arms, especially in SBb galaxies. Enhancements range from slight to factors $\sim$3, and may be quite different at the two bar ends.

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