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

Abstract

We present observations of the 36- (4_-1 -> 3_0E) and 84-GHz (5_-1 -> 4_0 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 density of the 36- and 84-GHz transitions are closely linked to the available gas volume.

MNRAS accepted 10 December 2018

References in corpus (7)

• A Class I and Class II Methanol Maser Survey of Extended Green Objects (EGOs) from the GLIMPSE Survey
• Class I methanol masers in the outflow of IRAS 16547-4247
• MALT-45: A 7 mm survey of the southern Galaxy - I. Techniques and spectral line data
• Class I methanol masers in NGC253: Alcohol at the end of the bar
• Class I Methanol (CH${}_3$OH) Maser Conditions near Supernova Remnants
• A catalog of 44 GHz methanol masers in massive star-forming regions. IV. The high-mass protostellar object sample
• MALT-45: A 7mm survey of the southern Galaxy - II. ATCA follow-up observations of 44GHz class I methanol masers

Cited by in corpus (4)

• Online Database of Class I Methanol Masers
• Discovery of six new class II methanol maser transitions, including the unambiguous detection of three torsionally excited lines toward G358.931-0.030
• 44 GHz methanol masers: Observations toward 95 GHz methanol masers
• Infrared study of the star-forming region associated with the UC HII regions G45.07+0.13 and G45.12+0.13