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For refcode 1996AJ....112.1903Y:
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1996AJ....112.1903Y THE GLOBAL RATE AND EFFICIENCY OF STAR FORMATION IN SPIRAL GALAXIES AS A FUNCTION OF MORPHOLOGY AND ENVIRONMENT JUDITH S. YOUNG, LORI ALLEN, JEFFREY D. P. KENNEY, AMY LESSER, AND BROOKS ROWND Department of Physics and Astronomy and Five College Radio Astronomy Observatory, University of Massachusetts, Amherst, Massachusetts 01003 Electronic mail: young@phast.umass.edu Received 1996 January 24; revised 1996 June 24 ABSTRACT CCD images of H{alpha} and R-band emission in 120 spiral galaxies were obtained using the now-retired No. 1-0.9 m telescope of Kitt Peak National Observatory. These images were used to derive the distribution and total flux of continuum-subtracted H{alpha} line emission, and therefore the H{alpha} surface brightnesses and high mass star formation rates in these galaxies. We find a small but significant variation in the mean H{alpha} surface brightness for spiral galaxies along the Hubble sequence; the Sd-Ir galaxies exhibit a mean H{alpha} surface brightness 1.4 times higher than the Sbc-Scd galaxies, and 2-3 times higher than the Sa-Sb galaxies. Estimates for the total formation rate for high mass stars have been compared with global molecular gas masses to determine the global efficiency of high mass star formation (= L_*_/M_gas_) as a function of morphological type and environment. We find that the mean efficiency of high mass star formation in this sample of spiral galaxies shows little dependence on morphological type for galaxies of type Sa through Scd, although there is a wide range in star formation efficiencies within each type. Galaxies in disturbed environments (i.e., strongly interacting systems) are found to have a mean star formation efficiency ~4 times higher than in isolated spiral galaxies, uncorrected for extinction. This confirms previous findings (Young et al. 1986a,b; Sanders et al. 1986; Solomon & Sage 1988; Tinney et al. 1990), based on the far-infrared luminosity rather than the H{alpha} luminosity to trace the rate of high mass star formation, that the mean star formation efficiency among isolated galaxies is significantly lower than that among interacting systems. This result provides further confirmation that the rate of high mass star formation is reasonably well traced by both the H{alpha} and the IR luminosity in spiral galaxies.
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