Dust emission versus dust attenuation in edge-on galaxies

The structural properties of the dust disks in galaxies can be explored using the attenuation by dust in the optical (via radiative transfer modeling) or using the emission of cold dust in the far-infrared (FIR). In this study, we conduct a comparative analysis of these two methods applied to a sample of edge-on galaxies. We demonstrate that these approaches give inconsistent results for the structural parameters of the dust disks. This fact can be important for addressing the so-called dust energy balance problem: the predicted FIR emission from radiative transfer models is underestimated by a factor of 2-5 as compared to the observed thermal emission at the same wavelengths. For our Galaxy and many other nearby spiral galaxies, it is well established that the stellar disks divide into thick and thin disks. For four best-resolved galaxies in our sample, NGC 891, NGC 3628, NGC 4437, and NGC 4631, we determine the structural properties of the thin and thick dust disks. The presence of the extraplanar emission in our FIR models may be one of the factors to explain the observed discrepancy in the results when using the different methods.