Methanol masers in the southern Galaxy
We have detected 6.6-GHz A+-methanol masers towards all nineteen 12.2-GHz E-methanol masers at declinations below -42°. We also searched all known OH masers in the longitude range 260° to 345° and detected 52 of 88. The detection rate of 6.6-GHz methanol masers is four times higher in the Norma area of the Galaxy than in the Carina arm. Although this may be partly due to sensitivity limitations, it may also be a product of the radial metallicity gradient in the Galaxy.
Fourteen 6.6-GHz masers with S6.6 ≥100 Jy were searched for associated 12.2-GHz E-methanol masers and four new masers were detected. The statistics of the non- detections suggest that there may not be a one-to-one correspondence of 6.6- to 12.2-GHz methanol masers.
We have reobserved five 12.2-GHz E-methanol masers, originally observed in 1987. We found that ≈80% of the maser components have varied by less that 10% over the four year period, implying that these masers are generally saturated. In several sources maser components have shifted in velocity.
KeywordsDetection Rate Methanol Molecule Fourth Quadrant Methanol Maser Radio Astronomy Observatory
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