Mid-infrared luminosity as an indicator of the total infrared luminosity of galaxies ^*

Laboratoire d'Astrophysique de Marseille, Traverse du Siphon, BP8, 13376 Marseille Cedex 12, France e-mail: [tsutomu.takeuchi;veronique.buat;jorge.iglesias;alessandro.boselli; denis.brugarella]@oamp.fr

Received: 15 October 2004
Accepted: 2 November 2004

Abstract

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 [CITE], L_TIR [CITE], revised version of L_TIR [CITE] (we denote L_TIR2), and L_IR [CITE] 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 [CITE] and found useful formulae relating the MIR monochromatic luminosities [ and ] and L_IR. For this purpose we constructed a subsample of 1420 galaxies with all four IRAS band (12, 25, 60, and m) flux densities. We found linear relations between L_IR and MIR luminosities, and . 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 m or m observations. We further tried to make an “interpolation” formula for galaxies at . 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 m observation of galaxies at .