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Date and Time of the Query: 2019-06-19 T12:54:25 PDT
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For refcode 1995AstL...21..652Z:
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Copyright by American Institute of Physics. 1995AstL...21..652Z The Efficiency of Star Formation in Spiral Galaxies A. V. Zasov Sternberg Astronomical Institute, Universitetskii pr 13, Moscow 119899 Russia Received February 8,1995; in final form, May 12,1995 Abstract - The relationship between the integrated luminosities of galaxies in the far-infrared (L_fir_) and H{alpha} (L_H{alpha}_), on the one hand, and the star formation rate (SFR), on the other hand, is discussed. Although both these luminosities are tightly linked with the number of young stars, their ratio L_fir_.L_H{alpha}_ varies over a wide range. For an optical sample of disk (predominantly spiral) galaxies, this ratio systematically grows with increasing color index, which may be associated with an increase in the upper limit on the mass of stars in the "bluest" galaxies. The relationship between L_fir_/L_B_ (L_B_ is the optical luminosity) and the color index (B - V)^0^_T_ for galaxies agrees well with the predicted dependence obtained from evolutionary simulations (Sil'chenko 1994) assuming that the SFR is proportional to L_fir_. The best agreement for a Salpeter initial mass function is obtained for the relation SFR = 2.5 x 10^-10^L_fir_/L_sun_(M_sun_/yr). The star formation efficiency SFE = SFR/M_gas_ is several times 10^-10^/yr for the majority of galaxies, without noticeable differences in the SFE for galaxies of early and late morphological type. The relative gas content in the galaxies M_HI+H_2_/L_B_ correlates weakly with the SFE; however, for many galaxies it is significantly lower than expected for the case in which the SFE is constant in time. It is concluded that in the past, galaxies proceeded through a period of rapid gas loss, evidently connected with the fact that not only the rate, but also the efficiency of star formation in an early stage of the evolution of galactic disks was significantly higher than at the present time.
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