Mapping the interstellar medium in galaxies with Herschel/SPIRE
  The standard method of mapping the interstellar medium in a galaxy, by
observing the molecular gas in the CO 1-0 line and the atomic gas in the 21-cm
line, is largely limited with current telescopes to galaxies in the nearby
universe. In this letter, we use SPIRE observations of the galaxies M99 and
M100 to explore the alternative approach of mapping the interstellar medium
using the continuum emission from the dust. We have compared the methods by
measuring the relationship between the star-formation rate and the surface
density of gas in the galaxies. We find the two methods give relationships with
a similar dispersion, confirming that observing the continuum emission from the
dust is a promising method of mapping the interstellar medium in galaxies.
