  We have used the Submillimeter Array to image a flux limited sample of seven
submillimeter galaxies, selected by the AzTEC camera on the JCMT at 1.1 mm, in
the COSMOS field at 890um with 2" resolution. All of the sources - two
radio-bright and five radio-dim - are detected as single point-sources at high
significance (> 6\sigma), with positions accurate to 0.2" that enable
counterpart identification at other wavelengths observed with similarly high
angular resolution. All seven have IRAC counterparts, but only two have secure
counterparts in deep HST/ACS imaging. As compared to the two radio-bright
sources in the sample, and those in previous studies, the five radio-dim
sources in the sample (1) have systematically higher submillimeter-to-radio
flux ratios, (2) have lower IRAC 3.6-8.0um fluxes, and (3) are not detected at
24um. These properties, combined with size constraints at 890um (\theta <
1.2"), suggest that the radio-dim submillimeter galaxies represent a population
of very dusty starbursts, with physical scales similar to local ultraluminous
infrared galaxies, and an average redshift higher than radio-bright sources.
