We report 3 mm continuum , CH _ { 3 } CN ( 5-4 ) and ^ { 13 } CS ( 2-1 ) line observations with CARMA , in conjunction with 6 and 1.3 cm continuum VLA data , and 12 and 25 \mu m broadband data from the Subaru Telescope toward the massive proto-star IRAS 18566 + 0408 .
The VLA data resolve the ionized jet into 4 components aligned in the E-W direction .
Radio components A , C , and D have flat cm SEDs indicative of optically thin emission from ionized gas , and component B has a spectral index \alpha = 1.0 , and a decreasing size with frequency \propto \nu ^ { -0.5 } .
Emission from the CARMA 3 mm continuum , and from the ^ { 13 } CS ( 2-1 ) , and CH _ { 3 } CN ( 5-4 ) spectral lines is compact ( i.e . < 6700 AU ) , and peaks near the position of VLA cm source , component B .
Analysis of these lines indicates hot , and dense molecular gas , typical for HMCs .
Our Subaru telescope observations detect a single compact source , coincident with radio component B , demonstrating that most of the energy in IRAS 18566+0408 originates from a region of size < 2400 AU .
We also present UKIRT near-infrared archival data for IRAS 18566+0408 which show extended K-band emission along the jet direction .
We detect an E-W velocity shift of about 10 km s ^ { -1 } over the HMC in the CH _ { 3 } CN lines possibly tracing the interface of the ionized jet with the surrounding core gas .
Our data demonstrate the presence of an ionized jet at the base of the molecular outflow , and support the hypothesis that massive protostars with O-type luminosity form with a mechanism similar to lower mass stars .