We present observations of the spiral galaxy NGC 7331 using the Sub-millimetre Common User Bolometer Array ( SCUBA ) on the James Clark Maxwell Telescope .
We have detected a dust ring of 45 arcsec radius ( 3.3 kpc ) at wavelengths of 450 and 850- \mu m. The dust ring is in good correspondence with other observations of the ring in the mid-infrared ( MIR ) , CO and radio-continuum , suggesting that the observed dust is associated with the molecular gas and star formation .
A B-K colour map shows an analogous ring structure with an asymmetry about the major axis , consistent with the extinction being produced by a dust ring .
The derived temperature of the dust lies between 16 and 31 K and the gas-to-dust ratio between 150 and 570 , depending on the assumed dust emission efficiency index ( \beta = 1.5 or 2 .
) .