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Stellar Mass Estimation Based on IRAC Photometry for Spitzer SWIRE-field Galaxies

We analyze the feasibility to estimate the stellar mass of galaxies by mid-infrared luminosities based on a large sample of galaxies cross-identified from $Spitzer$ SWIRE fields and SDSS spectrographic survey. We derived the formulae to calculate the stellar mass by using IRAC 3.6$μ$m and 4.5$μ$m luminosities. The mass-to-luminosity ratios of IRAC 3.6$μ$m and 4.5$μ$m luminosities are more sensitive to star formation history of galaxies than other factors, such as the intrinsic extinction, metallicity and star formation rate. To remove the affection from star formation history, we used g-r color to recalibrate the formulae and obtain a better result. It must be more careful to estimate the stellar mass of low metallicity galaxies using our formulae. Due to the emission from dust heated by hottest young stars, luminous infrared galaxies present higher IRAC 4.5 $μ$m luminosity compared to IRAC 3.6 $μ$m luminosity. For most of type-II AGNs, the nuclear activity can not enhance 3.6$μ$m and 4.5$μ$m luminosities compared with normal galaxies. The star formation in our AGN-hosting galaxies is also very weak, almost all of which are early-type galaxies.