The Giant Molecular Cloud associated with RCW 106 A 1 . 2 mm continuum mapping study

We have mapped the dust continuum emission from the molecular cloud covering a region of 28 pc×94 pc associated with the well-known H  region RCW 106 at 1.2 mm using SIMBA on SEST. The observations, having an HPBW of 24′′ (0.4 pc), reveal 95 clumps, of which about 50% have MSX associations and only 20% have IRAS associations. Owing to the higher sensitivity to colder dust and higher angular resolution the present observations identify new emission features and also show that most of the IRAS sources in this region consist of multiple dust emission peaks. The detected millimeter sources (MMS) include on one end the exotic MMS5 (associated with IRAS 16183-4958, one of the brightest infrared sources in our Galaxy) and the bright (and presumably cold) source MMS54, with no IRAS or MSX associations on the other end. Around 10% of the sources are associated with signposts of high mass star formation activity. Assuming a uniform dust temperature of 20 K we estimate the total mass of the GMC associated with RCW 106 to be ∼ 105 M⊙. The constituent millimeter clumps cover a range of masses and radii between 40 to 104 M⊙ and 0.3 to 1.9 pc. Densities of the clumps range between (0.5-6) 104 cm−3. We have decomposed the continuum emission into gaussian and arbitrary shaped clumps using the two independent structure analysis tools gaussclumps and clumpfind respectively. The clump mass spectrum was found to have an index α of 1.6 ± 0.3, independent of the decomposition algorithm used. The index of the mass spectrum for the mass and length scales covered here are consistent with results derived from large scale CO observations. 2 Mookerjea et al.: 1.2 mm study of RCW106