Herschel/SPIRE Observations of the Dusty Disk of NGC 4244
  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 Hi 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(dust) = 2 - 5
h(stars)), higher dust masses than previous models of NGC 4244 (Md = 0.47 -
1.39 \times 10e7 Msun) and a face-on optical depth of {\tau}(V) = 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 submm 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.
