We present a detailed analysis of the radial distribution of dust properties in the SINGS sample , performed on a set of UV , IR and HI surface brightness profiles , combined with published molecular gas profiles and metallicity gradients .
The internal extinction , derived from the TIR-to-FUV luminosity ratio , decreases with radius , and is larger in Sb-Sbc galaxies .
The TIR-to-FUV ratio correlates with the UV spectral slope \beta , following a sequence shifted to redder UV colors with respect to that of starbursts .
The star formation history ( SFH ) is identified as the main driver of this departure .
Both L _ { \mathrm { TIR } } / L _ { \mathrm { FUV } } and \beta correlate well with metallicity , especially in moderately face-on galaxies .
The relation shifts to redder colors with increased scatter in more edge-on objects .
By applying physical dust models to our radial SEDs , we have derived radial profiles of the total dust mass surface density , the fraction of the total dust mass contributed by PAHs and the intensity of the radiation field heating the grains .
The dust profiles are exponential , their radial scale-length being constant from Sb to Sd galaxies ( only \sim 10 % larger than the stellar scale-length ) .
Many S0/a-Sab galaxies have central depressions in their dust radial distributions .
The PAH abundance increases with metallicity for 12 + \log ( \mathrm { O / H } ) < 9 , and at larger metallicities the trend flattens and even reverses , with the SFH being a plausible underlying driver for this behavior .
The dust-to-gas ratio is also well correlated with metallicity and therefore decreases with galactocentric radius .
Although most of the total emitted IR power ( especially in the outer regions of disks ) is contributed by dust grains heated by diffuse starlight with a similar intensity as the local Milky Way radiation field , a small amount of the dust mass ( \sim 1 % ) is required to be exposed to very intense starlight in order to reproduce the observed fluxes at 24 \micron , accounting for \sim 10 % of the total integrated IR power .