We report the results of high-resolution ( \sim 0.2 pc ) CO ( 1–0 ) and CS ( 2–1 ) observations of the central regions of three star-forming molecular clouds in the far-outer Galaxy ( \sim 16 kpc from the Galactic Center ) : WB89 85 ( Sh 2-127 ) , WB89 380 , and WB89 437 .
We used the BIMA array in combination with IRAM 30-m and NRAO 12-m observations .
The GMC ’ s in which the regions are embedded were studied by means of KOSMA 3-m CO ( 2–1 ) observations ( here we also observed WB89 399 ) .
We compare the BIMA maps with optical , radio , and near-infrared observations .
Using a clumpfind routine , structures found in the CO and CS emission are subdivided in clumps , the properties of which are analyzed and compared with newly derived results of previously published single-dish measurements of local clouds ( OrionB South and Rosette ) .
We find that the slopes of the clump mass distributions ( –1.28 and –1.49 , for WB89 85 and WB89 380 , respectively ) are somewhat less steep than found for most local clouds , but similar to those of clouds which have been analyzed with the same clumpfind program .
We investigate the clump stability by using the virial theorem , including all possible contributions ( gravity , turbulence , magnetic fields , and pressure due to the interclump gas ) .
It appears that under reasonable assumptions a combination of these forces would render most clumps stable .
Comparing only gravity and turbulence , we find that in the far-outer Galaxy clouds , these forces are in equilibium ( virial parameter \alpha \approx 1 ) for clumps down to the lowest masses found ( a few M _ { \odot } ) .
For clumps in the local clouds \alpha \approx 1 only for clumps with masses larger than a few tens of M _ { \odot } .
Thus it appears that in these outer Galaxy clumps gravity is the dominant force down to a much lower mass than in local clouds , implying that gravitational collapse and star formation may occur more readily even in the smallest clumps .
Although there are some caveats , due to the inhomogeneity of the data used , this might explain the apparently steeper IMF found in the outer Galaxy .