The gas-to-dust mass ratio of Centaurus A as seen by Herschel
  We present photometry of the nearby galaxy NGC 5128 (Centaurus A) observed
with the PACS and SPIRE instruments on board the Herschel Space Observatory, at
70, 160, 250, 350 and 500 {\mu}m, as well as new CO J = 3-2 observations taken
with the HARP-B instrument on the JCMT. Using a single component modified
blackbody, we model the dust spectral energy distribution within the disk of
the galaxy using all five Herschel wavebands, and find dust temperatures of ~30
K towards the centre of the disk and a smoothly decreasing trend to ~20 K with
increasing radius. We find a total dust mass of (1.59 \pm 0.05) \times 10^7
M\odot, and a total gas mass of (2.7 \pm 0.2) \times 10^9 M\odot. The average
gas-to-dust mass ratio is 103 \pm 8 but we find an interesting increase in this
ratio to approximately 275 toward the centre of Cen A. We discuss several
possible physical processes that may be causing this effect, including dust
sputtering, jet entrainment and systematic variables such as the XCO factor.
Dust sputtering by X-rays originating in the AGN or the removal of dust by the
jets are our most favoured explanations.
