Gathering dust: A galaxy-wide study of dust emission from cloud
  complexes in NGC 300
  We used multi-band observations by the Herschel Space Observatory to study
the dust emission properties of the nearby spiral galaxy NGC 300. We compiled a
first catalogue of the population of giant dust clouds (GDCs) in NGC 300 and
give an estimate of the total dust mass of the galaxy. We carried out source
detection with the multiwavelength source extraction algorithm getsources and
calculated physical properties of the GDCs, including mass and temperature,
from five-band Herschel PACS and SPIRE observations from 100-500 $\mu$m; the
final size and mass estimates are based on the observations at 250 $\mu$m that
have an effective spatial resolution of $\sim$170 pc. We correlated our final
catalogue of GDCs to pre-existing catalogues of HII regions to infer the number
of GDCs associated with high-mass star formation and determined the H$\alpha$
emission of the GDCs. Our final catalogue of GDCs includes 146 sources, 90 of
which are associated with known HII regions. We find that the dust masses of
the GDCs are completely dominated by the cold dust component and range from
$\sim$1.1$\cdot$10$^{3}$ - 1.4$\cdot$10$^{4}$ M$_{\odot}$. The GDCs have
effective temperatures of $\sim$13-23 K and show a distinct cold dust effective
temperature gradient from the centre towards the outer parts of the stellar
disk. We find that the population of GDCs in our catalogue constitutes
$\sim$16% of the total dust mass of NGC 300, which we estimate to be about
5.4$\cdot$10$^{6}$ M$_{\odot}$. At least about 87% of our GDCs have a high
enough average dust mass surface density to provide sufficient shielding to
harbour molecular clouds. We compare our results to previous pointed molecular
gas observations in NGC 300 and results from other nearby galaxies and also
conclude that it is very likely that most of our GDCs are associated with
complexes of giant molecular clouds.
