Mon. Not. R. Astron. Soc., 484, 5072-5093 (2019/April-3)
84-GHz methanol masers, their relationship to 36-GHz methanol masers, and their molecular environments.
BREEN S.L., CONTRERAS Y., DAWSON J.R., ELLINGSEN S.P., VORONKOV M.A. and McCARTHY T.P.
Abstract (from CDS):
We present observations of the 36-GHz (4–1 - 30 E) and 84-GHz (5–1 - 40 E) class I methanol maser transitions towards a sample of 94 known class I sites. These observations resulted in 93 and 92 detections in the 84- and 36-GHz transitions. While the majority of the 36-GHz sources have been previously reported, many of the sites are observed in the 84-GHz transition for the first time. The near-simultaneous observations of the two transitions revealed strikingly similar spectral profiles and a mean and median 36- to 84-GHz integrated flux density ratio of 2.6 and 1.4. Alongside the 36- and 84-GHz observations, we included rare class II methanol masers at 37.7, 38.3, 38.5, 86.6, and 86.9 GHz, a number of recombination lines, and thermal molecular transitions. We detect one new site of 86.6- and 86.9-GHz methanol masers, as well as six maser candidates in one or more of 37.7-, 38.3-, 38.5-, 86.6-, and 86.9-GHz methanol maser transitions. We detect a relatively higher rate of HC3N compared to that reported by MALT90 (once the respective detection limits were taken into account), who targeted dense dust clumps, suggesting that the class I methanol maser targets incorporate a relatively higher number of warm protostellar sources. We further find that there are similar relationships between the integrated flux density of both class I transitions with the integrated intensity of HC3N, HNC, HCO+, HNC, SiO, and H13CO+. We suggest that this indicates that the integrated flux densities of the 36- and 84-GHz transitions are closely linked to the available gas volume.
© 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society
masers - stars: formation - ISM: molecules - radio lines: ISM
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