First Interferometric Images of the 36 GHz Methanol Masers in the DR21
  Complex
  Class I methanol masers are believed to be produced in the shock-excited
environment around star-forming regions. Many authors have argued that the
appearance of various subsets of class I masers may be indicative of specific
evolutionary stages of star formation or excitation conditions. Until recently,
however, no major interferometer was capable of imaging the important 36 GHz
transition. We report on Expanded Very Large Array observations of the 36 GHz
methanol masers and Submillimeter Array observations of the 229 GHz methanol
masers in DR21(OH), DR21N, and DR21W. The distribution of 36 GHz masers in the
outflow of DR21(OH) is similar to that of the other class I methanol
transitions, with numerous multitransition spatial overlaps. At the site of the
main continuum source in DR21(OH), class I masers at 36 and 229 GHz are found
in virtual overlap with class II 6.7 GHz masers. To the south of the outflow,
the 36 GHz masers are scattered over a large region but usually do not appear
coincident with 44 GHz masers. In DR21W we detect an "S-curve" signature in
Stokes V that implies a large value of the magnetic field strength if
interpreted as due to Zeeman splitting, suggesting either that class I masers
may exist at higher densities than previously believed or that the direct
Zeeman interpretation of S-curve Stokes V profiles in class I masers may be
incorrect. We find a diverse variety of different maser phenomena in these
sources, suggestive of differing physical conditions among them.
