  The relation between the ratio of infrared (IR) and ultraviolet (UV) flux
densities (the infrared excess: IRX) and the slope of the UV spectrum (\beta)
of galaxies plays a fundamental role in the evaluation of the dust attenuation
of star forming galaxies especially at high redshifts. Many authors, however,
pointed out that there is a significant dispersion and/or deviation from the
originally proposed IRX-\beta relation depending on sample selection. We
reexamined the IRX-\beta relation by measuring the far- and near-UV flux
densities of the original sample galaxies with GALEX and AKARI imaging data,
and constructed a revised formula. We found that the newly obtained IRX values
were lower than the original relation because of the significant
underestimation of the UV flux densities of the galaxies, caused by the small
aperture of IUE, Further, since the original relation was based on IRAS data
which covered a wavelength range of \lambda = 42--122\mum, using the data from
AKARI which has wider wavelength coverage toward longer wavelengths, we
obtained an appropriate IRX-\beta relation with total dust emission (TIR):
\log(L_{\rm TIR}/L_{\rm FUV}) = \log [10^{0.4(3.06+1.58\beta)}-1] +0.22. This
new relation is consistent with most of the preceding results for samples
selected at optical and UV, though there is a significant scatter around it. We
also found that even the quiescent class of IR galaxies follows this new
relation, though luminous and ultraluminous IR galaxies distribute completely
differently as well known before.
