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Description
We present Very Large Array and Atacama Large Millimeter/submillimeter Array imaging of the deeply embedded protostellar cluster NGC 6334I from 5cm to 1.3mm at angular resolutions as fine as 0.17" (220au). The dominant hot core MM1 is resolved into seven components at 1.3mm, clustered within a radius of 1000au. Four of the components have brightness temperatures >200K, radii ~300au, minimum luminosities ~10^4^L_{sun}_, and must be centrally heated. We term this new phenomenon a "hot multi-core." Two of these objects also exhibit compact free-free emission at longer wavelengths, consistent with a hypercompact HII region (MM1B) and a jet (MM1D). The spatial kinematics of the water maser emission centered on MM1D are consistent with it being the origin of the high-velocity bipolar molecular outflow seen in CO. The close proximity of MM1B and MM1D (440au) suggests a proto-binary or a transient bound system. Several components of MM1 exhibit steep millimeter spectral energy distributions indicative of either unusual dust spectral properties or time variability. In addition to resolving MM1 and the other hot core (MM2) into multiple components, we detect five new millimeter and two new centimeter sources. Water masers are detected for the first time toward MM4A, confirming its membership in the protocluster. With a 1.3mm brightness temperature of 97K coupled with a lack of thermal molecular line emission, MM4A appears to be a highly optically thick 240L_{sun}_ dust core, possibly tracing a transient stage of massive protostellar evolution. The nature of the strongest water maser source CM2 remains unclear due to its combination of non-thermal radio continuum and lack of dust emission.
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