The massive clump G10.6-0.4 is an OB cluster forming region , in which multiple UC H ii regions have been identified .
In the present study , we report arcsecond resolution observations of the CS ( 1–0 ) transition , the NH _ { 3 } ( 3,3 ) main hyperfine inversion transition , the CH _ { 3 } OH J=5 transitions , and the centimeter free–free continuum emissions in this region .
The comparisons of the molecular line emissions with the free–free continuum emissions reveal a 0.5 pc scale massive molecular envelope which is being partially dispersed by the dynamically–expanding bipolar ionized cavity .
The massive envelope is rotationally flattened and has an enhanced molecular density in the mid–plane .
In the center of this massive clump lies a compact ( < 0.1 pc ) hot ( \gtrsim 100 K ) toroid , in which a cluster of O–type stars has formed .

This overall geometry is analogous to the standard core collapse picture in the low–mass star forming region , with a central ( proto– ) stellar object , a disk , an envelope , and a bipolar outflow and outflow cavity .
However , G10.6-0.4 has a much larger physical size scale ( \leq 0.1 pc for typical low–mass star forming core ) .
Based on the observations , we propose a schematic picture of the OB cluster forming region , which incorporates the various physical mechanisms .
This model will be tested with the observations of other embedded OB clusters , and with numerical simulations .