We present Herschel/SPIRE images at 250 , 350 , and 500 \mu m of NGC 4244 , a typical low-mass , disk-only and edge-on spiral galaxy .
The dust disk is clumpy and shows signs of truncation at the break radius of the stellar disk .
This disk coincides with the densest part of the H i disk .
We compare the Spectral Energy Distribution , including the new SPIRE fluxes , to 3D radiative transfer models ; a smooth model disk and a clumpy model with embedded heating .
Each model requires a very high value for the dust scale-length ( h _ { d } = 2 - 5 ~ { } h _ { * } ) , higher dust masses than previous models of NGC 4244 ( M _ { d } = 0.47 - 1.39 \times 10 ^ { 7 } M _ { \odot } ) and a face-on optical depth of \tau _ { V } ^ { f . o . } = 0.4 - 1.12 , in agreement with previous disk opacity studies .
The vertical scales of stars and dust are similar .
The clumpy model much better mimics the general morphology in the sub-mm images and the general SED .
The inferred gas-to-dust mass ratio is compatible with those of similar low-mass disks .
The relatively large radial scale-length of the dust disk points to radial mixing of the dusty ISM within the stellar disk .
The large vertical dust scale and the clumpy dust distribution of our SED model are both consistent with a scenario in which the vertical structure of the ISM is dictated by the balance of turbulence and self-gravity .