We characterize the dust in NGC 628 and NGC 6946 , two nearby spiral galaxies in the KINGFISH sample .
With data from 3.6 \mu m  to 500 \mu m , dust models are strongly constrained .
Using the dust model , ( amorphous silicate and carbonaceous grains ) , for each pixel in each galaxy we estimate ( 1 ) dust mass surface density , ( 2 ) dust mass fraction contributed by polycyclic aromatic hydrocarbons ( PAH ) s , ( 3 ) distribution of starlight intensities heating the dust , ( 4 ) total infrared ( IR ) luminosity emitted by the dust , and ( 5 ) IR luminosity originating in regions with high starlight intensity .
We obtain maps for the dust properties , which trace the spiral structure of the galaxies .
The dust models successfully reproduce the observed global and resolved spectral energy distributions ( SEDs ) .
The overall dust/H mass ratio is estimated to be 0.0082 \pm 0.0017 for NGCÂ 628 , and 0.0063 \pm 0.0009 for NGCÂ 6946 , consistent with what is expected for galaxies of near-solar metallicity .
Our derived dust masses are larger ( by up to a factor 3 ) than estimates based on single-temperature modified blackbody fits .
We show that the SED fits are significantly improved if the starlight intensity distribution includes a ( single intensity ) “ delta function ” component .
We find no evidence for significant masses of cold dust ( T \lesssim 12 K ) .
Discrepancies between PACS and MIPS photometry in both low and high surface brightness areas result in large uncertainties when the modeling is done at PACS resolutions , in which case SPIRE , MIPS70 and MIPS160 data can not be used .
We recommend against attempting to model dust at the angular resolution of PACS .