2005A&A...432..423T

The infrared (IR) emission plays a crucial role in understanding the star formation in galaxies hidden by dust. We first examined four estimators of the IR luminosity of galaxies, L_FIR (Helou et al., 1988ApJS...68..151H), L_TIR (Dale et al., 2001ApJ...549..215D), revised version of L_TIR (Dale et al., 2002ApJ...576..159D) (we denote L_TIR2), and L_IR (Sanders & Mirabel, 1996ARA&A..34..749S) by using the observed SEDs of well-known galaxies. We found that L_IR provides excellent estimates of the total IR luminosity for a variety of galaxy SEDs. The performance of L_TIR2 was also found to be very good. Using L_IR, we then statistically analyzed the IRAS PSCz galaxy sample (Saunders et al., 2000MNRAS.317...55S) and found useful formulae relating the MIR monochromatic luminosities [L(12µm) and L(25µm)] and L_IR. For this purpose we constructed a subsample of 1420 galaxies with all four IRAS band (12, 25, 60, and 100µm) flux densities. We found linear relations between L_IR and MIR luminosities, L(12µm) and L(25µm). The prediction error with a 95% confidence level is a factor of 4-5. Hence, these formulae are useful for the estimation of the total IR luminosity only from 12µm or 25µm observations. We further tried to make an ``interpolation'' formula for galaxies at 0<z<1. For this purpose we construct the formula of the relation between 15-µm luminosity and the total IR luminosity. We conclude that the 15-µm formula can be used as an estimator of the total IR luminosity from 24µm observation of galaxies at z≃0.6.