Astronomy and Astrophysics, volume 453, 1003-1026 (2006/7-3)
A SCUBA imaging survey of ultracompact HII regions. The environments of massive star formation.
THOMPSON M.A., HATCHELL J., WALSH A.J., MacDONALD G.H. and MILLAR T.J.
Abstract (from CDS):
We present a SCUBA submillimetre (450 and 850µm) survey of the environment of 105 IRAS point sources, selected from the Wood & Churchwell (1989ApJS...69..831W
) and Kurtz et al. (1994ApJS...91..659K
) radio ultracompact (UC) HII 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 HII regions unless they are located at large heliocentric distances. Many of the 2.5' 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 3pc. 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 HII 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 HII region phase, we argue that their characteristics are suggestive of such a stage.
stars: formation - ISM: HII regions - ISM: dust, extinction - submillimeter - radio continuum: ISM
VizieR on-line data:
<Available at CDS (J/A+A/453/1003): table1.dat table2.dat refs.dat
Table 2, col.(2): [THW2006] GLLL.lll+BB.bbbSMM N=159 = Table 2, col.(1): [THW2006] GLL.ll+BB.bb a N=159.
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