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 \sim 30 K towards the centre of the disk and a smoothly decreasing trend to \sim 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 X _ { \mathrm { CO } } factor .
Dust sputtering by X-rays originating in the AGN or the removal of dust by the jets are our most favoured explanations .