Submillimeter observations of Midcourse Space Experiment galactic infrared-dark clouds

We present 850 and 450 mum continuum images of infrared-dark clouds (IRDCs) taken with the Submillimeter Common-User Bolometer Array (SCUBA) submillimeter camera at the James Clerk Maxwell Telescope. The IRDCs are large (1-10 pc diameter) molecular cores with gas densities similar to 10(6) cm(-3) and temperatures approximate to 15 K. We detected strong submillimeter sources with peak flux densities of approximate to1 Jy beam(-1) at 850 mum in all eight clouds that were observed. The submillimeter emission generally lies within the envelope of the mid-infrared extinction where dense gas has been detected using H(2)CO as a tracer. The dust temperatures in the bright, compact sources are calculated to lie in the range 10-25 K. The masses of these sources are estimated to be in the range of several tens up to about a thousand solar masses. The corresponding gas column densities range over an order of magnitude, up to about 10(23) cm(-2). Several of the sources are detected in emission at both 850 and 8 mum Two of the sources have HCO(+) line profiles characteristic of molecular infall. It is likely that the bright, compact sources seen in the SCUBA images are in various early stages of star formation, from preprotostellar cores to class I objects.