First Interferometric Images of the 36 GHz Methanol Masers in the DR21 Complex

Abstract

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.

8 pages, accepted for publication in ApJ

References in corpus (5)

• Class I methanol masers in the outflow of IRAS 16547-4247
• A new probe of magnetic fields during high-mass star formation: Zeeman splitting of 6.7 GHz methanol masers
• Methanol Maser Polarization in W3(OH)
• High-velocity feature of the class I methanol maser in G309.38-0.13
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Cited by in corpus (24)

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• The Protocluster G18.67+0.03: A Test Case for Class I Methanol Masers as Evolutionary Indicators for Massive Star Formation
• Expanded Very Large Array Detection of 44.1 GHz Class I Methanol Masers in Sagittarius A
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• A 95 GHz Class I Methanol Maser Survey Toward A Sample of GLIMPSE Point Sources Associated with BGPS Clumps
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• Submillimeter Array Observations of NGC 2264-C: Molecular Outflows and Driving Sources
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• First Interstellar HCO${}^{+}$ Maser
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• Comparison of Two Epochs of the Zeeman Effect in the 44 GHz Class I methanol (CH3OH) maser line in OMC-2
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• SMA line observations of the CH${}_3$OH-maser outflow in DR21(OH)
• Polarisation of Class II Methanol Masers
• Masers in star forming regions
• Very Large Array Detection of the 36 GHz Zeeman Effect in DR21W Revisited