Images of star-forming regions. III. Sources in the NGC 7538 molecular cloud complex

Deep optical CCD images of the embedded infrared sources associated with NGC 7538 are presented. A reflected image of IRS 1, the most luminous infrared source in the region, is shown to be positionally offset from the VLA radio source in a direction that is consistent with that of the blueshifted portion of the bipolar molecular outflow toward the north. Maps of the IRS 1 region at 1.65 and 2.2 microns, made with a prototype infrared camera, confirm the positional displacement. The H-K color of IRS 1 is extremely red (greater than 5 mag), which shows that the radio source is indeed totally obscured at wavelengths less than 1.5 micron. This is also consistent with other estimates of the extinction to IRS 1. New VLA radio images of IRS 2 and IRS 3 are also presented. The peculiar object IRS 9, a source that displays deep absorption due to CO molecules in the solid phase, is associated with a diffuse optical nebula that corresponds with the infrared reflection nebula found by Werner et al. (1979). The young stellar objects in NGC 7538 represent a broad evolutionary range in high-mass star formation, from a fully evolved blister-type H II region to much younger objects which have yet to break through their protostellar cocoons. 35 references