2013ApJ...762...64G

We measure the integrated contributions of dusty asymptotic giant branch (AGB) stars and other luminous red mid-IR sources to the mid-IR luminosities of six galaxies (M81, NGC 2403, NGC 300, M33, and the Magellanic Clouds). We find the dusty AGB stars whose mid-IR fluxes are dominated by dust rather than photospheric emission contribute from 0.6% (M81) to 5.6% (SMC) of the 3.6 µm flux and 1.0% (M81) to 10.1% (SMC) of the 4.5 µm flux. We find a trend of decreasing AGB contribution with increasing galaxy metallicity, luminosity, and mass, and decreasing specific star formation rate (SSFR). However, these galaxy properties are strongly correlated in our sample and the simplest explanation of the trend is galaxy metallicity. Bright, red sources other than dusty AGB stars represent a smaller fraction of the luminosity, ∼1.2% at 3.6 µm, however, their dust is likely cooler and their contributions are likely larger at longer wavelengths. Excluding the SMC, the contribution from these red sources correlates with the SSFR as we would expect for massive stars. In total, after correcting for dust emission at other wavelengths, the dust around AGB stars radiates 0.1%-0.8% of the bolometric luminosities of the galaxies. Thus, hot dust emission from AGB and other luminous dusty stars represent a small fraction of the total luminosities of the galaxies but a significant fraction of their mid-IR emissions.