COLD DUST IN HOT REGIONS

We mapped five massive star-forming regions with the SCUBA-2 camera on the James Clerk Maxwell Telescope. Temperature and column density maps are obtained from the SCUBA-2 450 and 850 mu m images. Most of the dense clumps we find have central temperatures below 20 K, with some as cold as 8 K, suggesting that they have no internal heating due to the presence of embedded protostars. This is surprising, because at the high densities inferred from these images and at these low temperatures such clumps should be unstable, collapsing to form stars and generating internal heating. The column densities at the clump centers exceed 10(23) cm(-2), and the derived peak visual extinction values are from 25 to 500 mag for beta = 1.5-2.5, indicating highly opaque centers. The observed cloud gas masses range from similar to 10 to 10(3) M-circle dot. The outer regions of the clumps follow an r(-2.36 +/- 0.35) density distribution, and this power-law structure is observed outside of typically 10(4) AU. All these findings suggest that these clumps are high-mass starless clumps and most likely contain high-mass starless cores.