The JCMT Nearby Galaxies Legacy Survey III: Comparisons of cold dust,
  polycyclic aromatic hydrocarbons, molecular gas, and atomic gas in NGC 2403
  We used 3.6, 8.0, 70, 160 micron Spitzer Space Telescope data, James Clerk
Maxwell Telescope HARP-B CO J=(3-2) data, National Radio Astronomy Observatory
12 meter telescope CO J=(1-0) data, and Very Large Array HI data to investigate
the relations among PAHs, cold (~20 K) dust, molecular gas, and atomic gas
within NGC 2403, an SABcd galaxy at a distance of 3.13 Mpc. The dust surface
density is mainly a function of the total (atomic and molecular) gas surface
density and galactocentric radius. The gas-to-dust ratio monotonically
increases with radius, varying from ~100 in the nucleus to ~400 at 5.5 kpc. The
slope of the gas-to-dust ratio is close to that of the oxygen abundance,
suggesting that metallicity strongly affects the gas-to-dust ratio within this
galaxy. The exponential scale length of the radial profile for the CO J=(3-2)
emission is statistically identical to the scale length for the stellar
continuum-subtracted 8 micron (PAH 8 micron) emission. However, CO J=(3-2) and
PAH 8 micron surface brightnesses appear uncorrelated when examining sub-kpc
sized regions.
