We report the first sub-arcsecond VLA imaging of 6 GHz continuum , methanol maser , and excited-state hydroxyl maser emission toward the massive protostellar cluster NGC6334I following the recent 2015 outburst in ( sub ) millimeter continuum toward MM1 , the strongest ( sub ) millimeter source in the protocluster .
In addition to detections toward the previously known 6.7 GHz Class II methanol maser sites in the hot core MM2 and the UCHII region MM3 ( NGC6334F ) , we find new maser features toward several components of MM1 , along with weaker features \sim 1 ^ { \prime \prime } north , west , and southwest of MM1 , and toward the non-thermal radio continuum source CM2 .
None of these areas have heretofore exhibited Class II methanol maser emission in three decades of observations .
The strongest MM1 masers trace a dust cavity , while no masers are seen toward the strongest dust sources MM1A , 1B and 1D .
The locations of the masers are consistent with a combination of increased radiative pumping due to elevated dust grain temperature following the outburst , the presence of infrared photon propagation cavities , and the presence of high methanol column densities as indicated by ALMA images of thermal transitions .
The non-thermal radio emission source CM2 ( 2 ^ { \prime \prime } north of MM1 ) also exhibits new maser emission from the excited 6.035 and 6.030 GHz OH lines .
Using the Zeeman effect , we measure a line-of-sight magnetic field of +0.5 to +3.7 mG toward CM2 .
In agreement with previous studies , we also detect numerous methanol and excited OH maser spots toward the UCHII region MM3 , with predominantly negative line-of-sight magnetic field strengths of -2 to -5 mG and an intriguing south-north field reversal .