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Session 63 - Galaxy Evolution II.
Oral session, Tuesday, January 16
Corte Real, Hilton

[63.04] Massive Star Formation Properites of Virgo Cluster and Isolated Spiral Galaxies

R. A. Koopmann, J. D. P. Kenney (Yale)

The star formation properties as traced by CCD H\alpha images are discussed for 65 Virgo Cluster spiral galaxies and a control sample of 35 isolated spirals. We present analyses of surface brightness profiles, asymmetries in the distribution of star formation, and star formation along bars.

Virgo Cluster Sc spirals display a larger scatter in H\alpha surface brightness across the disk than isolated Sc galaxies, indicating that a number of environmental processes have affected Virgo disks. In the outer disks, the scatter is a factor of 2 larger in the Virgo Cluster sample, and is due mostly to truncated star-forming disks in HI-deficient galaxies. In the inner disks, the scatter is greater by a factor of 3-4 and is attributable to diminished star formation in anemic galaxies and enhanced star formation in tidally interacting galaxies and several HI-rich galaxies which may be accreting gas.

Star formation along the bar occurs with the same frequency in both samples, but the H\alpha luminosity of the star forming regions is enhanced in the Virgo Cluster sample. The overall star formation distribution in these galaxies tends to be more asymmetric than in their isolated counterparts. These results are consistent with young bars, possibly created by tidal interactions.

Program listing for Tuesday