84-GHz methanol masers, their relationship to 36-GHz methanol masers, and their molecular environments

S. L. Breen*, Y. Contreras, J. R. Dawson, S. P. Ellingsen, M. A. Voronkov, T. P. McCarthy

*Corresponding author for this work

Research output: Contribution to journalArticle

3 Citations (Scopus)
22 Downloads (Pure)

Abstract

We present observations of the 36-GHz (4₋₁→3₀E) and 84-GHz (5₋₁→4₀E) 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 HC 3 N 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.

Original languageEnglish
Pages (from-to)5072-5093
Number of pages22
JournalMonthly Notices of the Royal Astronomical Society
Volume484
Issue number4
Early online date21 Jan 2019
DOIs
Publication statusPublished - Apr 2019

Bibliographical note

This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society, Volume 484, Issue 4, 21 April 2019, Pages 5072–5093, https://doi.org/10.1093/mnras/stz192. Copyright 2019 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

Keywords

  • ISM: molecules
  • masers
  • radio lines: ISM
  • stars: formation

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