  Infrared (IR) luminosity of galaxies originating from dust emission can be
used as an indicator of the star formation rate (SFR). Inoue et al. (2000, IHK)
have derived a formula for the conversion from IR luminosity to SFR by using
the following three quantities: the fraction of Lyman continuum luminosity
absorbed by gas (f), the fraction of UV luminosity absorbed by dust (epsilon),
and the fraction of dust heating from old (>10^8 yr) stellar populations (eta).
We develop a method to estimate those three quantities based on the idea that
the various way of SFR estimates should return the same SFR. After applying our
method to samples of galaxies, the following results are obtained. First, our
method is applied to star-forming galaxies, finding that f~0.6, epsilon~0.5,
and eta~0.4 as representative values. Next, we apply the method to a starburst
sample, which shows larger extinction than the star-forming galaxy sample. With
the aid of f, epsilon, and eta, we estimate reliable SFRs. Moreover, the
H-alpha luminosity, if the H-alpha extinction is corrected by using the Balmer
decrement, is suitable for a statistical analysis of SFR, because the same
correction factor for the Lyman continuum extinction is applicable to both
normal and starburst galaxies over all the range of SFR. The metallicity
dependence of f and epsilon is also tested: Only the latter proves to have a
correlation with metallicity. As an extension of our result, we show that all
UV, H-alpha, and IR comoving luminosity densities at z=0 give a consistent SFR
(~ 3x10^{-2}h M_sun/Mpc^3). Useful formulae for SFR estimate are listed.
