We present a SCUBA submillimetre ( 450 & 850 \mu m ) survey of the environment of 105 IRAS point sources , selected from the Wood & Churchwell ( [ 1989a ] ) and Kurtz , Churchwell & Wood ( [ 1994 ] ) radio ultracompact ( UC ) H ii region surveys .
We detected a total of 155 sub-mm clumps associated with the IRAS point sources and identified three distinct types of object : ultracompact cm-wave sources that are not associated with any sub-mm emission ( sub-mm quiet objects ) , sub-mm clumps that are associated with ultracompact cm-wave sources ( radio-loud clumps ) ; and sub-mm clumps that are not associated with any known ultracompact cm-wave sources ( radio-quiet clumps ) .
90 % of the sample of IRAS point sources were found to be associated with strong sub-mm emission .
We consider the sub-mm colours , morphologies and distance-scaled fluxes of the sample of sub-mm clumps and show that the sub-mm quiet objects are unlikely to represent embedded UC H ii regions unless they are located at large heliocentric distances .
Many of the 2 \aas@@fstack { \prime } 5 SCUBA fields contain more than one sub-mm clump , with an average number of companions ( the companion clump fraction ) of 0.90 .
The clumps are more strongly clustered than other candidate HMPOs and the mean clump surface density exhibits a broken power-law distribution with a break at 3 pc .
We demonstrate that the sub-mm and cm-wave fluxes of the majority of radio-loud clumps are in excellent agreement with the standard model of ultracompact H ii regions .
We speculate on the nature of the radio-quiet sub-mm clumps and , whilst we do not yet have sufficient data to conclude that they are in a pre-UC H ii region phase , we argue that their characteristics are suggestive of such a stage .