Dissecting the Global Cold Dust Properties and Possible Submillimeter Excess of 13 Nearby Spiral Galaxies from the NGLS

We select 13 nearby spiral galaxies from the Nearby Galaxies Legacy Survey (NGLS) project and perform spectral energy distribution fitting for each galaxy applying two-component modified blackbody models on a global scale aim to probe the potential submillimeter (submm) excess. We find that NGC 2976, NGC 3351, and NGC 4631 show excess emission at 850 m when using βc = 2.0. The contributions of CO(3-2), free-free emission or synchrotron radiation cannot explain their 850 m excess. Our results suggest that a submm excess at 850 m may be more easily detected for galaxies with faint total infrared luminosity and low cold dust mass. The colder temperature of cold dust, the more radiation of dust there is at 850 m. The submm excess are prone to be detected in spiral galaxies with low stellar mass. As the metallicity of galaxies become poor, the submm excess is more obvious.