The massive star formation properties of 55 Virgo Cluster and 29 isolated S0-Scd bright (M(B) < -18) spiral galaxies are compared via analyses of R and Halpha surface photometry and integrated fluxes as functions of Hubble type and central R light concentration (bulge-to-disk ratio). In the median, the total normalized massive star formation rates (NMSFRs) in Virgo Cluster spirals are reduced by factors up to 2.5 compared to isolated spiral galaxies of the same type or concentration, with a range from enhanced (up to 2.5 times) to strongly reduced (up to 10 times). Within the inner 30% of the optical disk, Virgo Cluster and isolated spirals have similar ranges in NMSFRs, with similar to enhanced median NMSFRs for Virgo galaxies. NMSFRs in the outer 70% of the optical disk are reduced in the median by factors up to 9 for Virgo Cluster spirals, with more severely reduced star formation at progressively larger disk radii. Thus the reduction in total star formation of Virgo Cluster spirals is caused primarily by spatial truncation of the star-forming disks. The correlation between HI deficiency and R light central concentration is much weaker than the correlation between HI deficiency and Hubble type. ICM-ISM stripping of the gas from spiral galaxies is likely responsible for the truncated star-forming disks of Virgo Cluster spirals. This effect may be responsible for a significant part of the morphology-density relationship.
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