Models of class II methanol masers based on improved molecular data

Cragg, D. M.; Соболев, А. М.; Godfrey, Peter D.

doi:10.1111/j.1365-2966.2005.09077.x

Cited by 280 publications

(382 citation statements)

References 38 publications

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“…Norris et al 1993;Moscadelli et al 2002). The physical conditions required to produce the 6.7-and 12.2-GHz methanol masers are similar, but do not cover exactly the same parameter space (Cragg, Sobolev & Godfrey 2005), making the combination of the two transitions especially useful. Furthermore, since 12.2-GHz methanol masers are almost always found to have lower flux densities than their 6.7-GHz counterparts and the fact that there have been no serendipitous detections of 12.2-GHz methanol masers without 6.7 GHz, a complete sample of 12.2-GHz methanol masers can be gained by targeting a complete sample of 6.7-GHz masers.…”

Section: Introductionmentioning

confidence: 93%

12.2-GHz methanol maser MMB follow-up catalogue – IV. Longitude range 20°–60°

Breen

Ellingsen

Caswell

et al. 2016

Mon. Not. R. Astron. Soc.

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This is the fourth and final instalment of a series of catalogues presenting 12.2-GHz methanol maser observations made towards each of the 6.7-GHz methanol masers detected in the Methanol Multibeam (MMB) survey. This final portion of the survey covers the 20 • -60 • longitude range, increasing the 12.2-GHz follow-up range to the full MMB coverage of 186 • ≥ l ≤ 60 • and |b| ≤ 2 • . Towards a total of 260 6.7-GHz MMB methanol masers (we were unable to observe five of the MMB sources in this longitude range) we detect 116 12.2-GHz masers counterparts, 64 of which were discovered in this survey. Including data from the literature, we find that there are 12.2-GHz methanol masers towards 47.1 per cent of the 6.7-GHz methanol masers in this portion of the Galaxy. Across the entire MMB survey range, we find a detection rate of 45.3 per cent. We find that the detection rate of 12.2-GHz methanol masers as a function of Galactic longitude is not uniform and there is an excess of masers with broad velocity ranges at longitudes near 30 • and 330 • . Comparing the occurrence of 12.2-GHz methanol masers with MMB-targeted CO observations has shown that those outflows associated with a 12.2-GHz source have a larger average dynamical time-scale than those associated with only 6.7-GHz methanol masers, supporting the notion that the 12.2-GHz masers are associated with a later phase of high-mass star formation.

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Section: Introductionmentioning

confidence: 93%

12.2-GHz methanol maser MMB follow-up catalogue – IV. Longitude range 20°–60°

Breen

Ellingsen

Caswell

et al. 2016

Mon. Not. R. Astron. Soc.

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“…3 caption for a general explanation of box plots. Cragg, Sobolev & Godfrey (2005) presented maser modelling of class II methanol masers and their figs 2 and 3 show how maser brightness varies with a number of parameters, including dust temperature, which shows a sharp increase in maser brightness at a higher dust temperature for 12.2-GHz methanol masers compared to 6.7-GHz methanol masers. Their findings are naively consistent with our results, showing that sources associated with both 6.7-and 12.2-GHz methanol masers have slightly warmer dust temperatures, however, there are a number of complex factors at play, including the fact that these parameter plots show how dust temperature varies as other parameters remain fixed, and the fact that our dust temperatures represent the average of a significant region.…”

Section: Comparison With Maser Modelsmentioning

confidence: 99%

The 6-GHz Multibeam Maser Survey – III. Comparison between the MMB and HOPS

Breen

Contreras

Ellingsen

et al. 2017

Monthly Notices of the Royal Astronomical Society

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We have compared the occurrence of 6.7-GHz and 12.2-GHz methanol masers with 22-GHz water masers and 6035-MHz excited-state OH masers in the 100 square degree region of the southern Galactic plane common to the Methanol Multibeam (MMB) and H 2 O southern Galactic Plane surveys (HOPS). We find the most populous star formation species to be 6.7-GHz methanol, followed by water, then 12.2-GHz and, finally, excited-state OH masers. We present association statistics, flux density (and luminosity where appropriate) and velocity range distributions across the largest, fully surveyed portion of the Galactic plane for four of the most common types of masers found in the vicinity of star formation regions.Comparison of the occurrence of the four maser types with far-infrared dust temperatures shows that sources exhibiting excited-state OH maser emission are warmer than sources showing any of the other three maser types. We further find that sources exhibiting both 6.7-GHz and 12.2-GHz methanol masers are warmer than sources exhibiting just 6.7-GHz methanol maser emission. These findings are consistent with previously made suggestions that both OH and 12.2-GHz methanol masers generally trace a later stage of star formation compared to other common maser types.

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“…The class II methanol masers are thought to be pumped by infrared radiation (Cragg et al 2005) and found to originate in accretion disks in highmass star-forming regions (Sanna et al 2010;Sugiyama et al 2014). The similarity in the variability found in the methanol maser emission (MME) and the IR variability may therefore represent the frequency of the infrared luminosity variations of the warm disk from accretion events, which is also responsible for pumping the class II MME (Cragg et al 2005). We searched for MME in the 13 VYSOs and did not find any methanol masers within a radius of 30″.…”

Section: Discussionmentioning

confidence: 99%

Highly Variable Young Massive Stars in Atlasgal Clumps

Kumar

Peña

Lucas

2016

ApJ

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High-amplitude variability in young stellar objects (YSOs) is usually associated with episodic accretion events. It has not been observed so far in massive YSOs. Here, the high-amplitude variable star sample of Contreras Peña et al. has been used to search for highly variable (ΔK 1 mag) sources coinciding with dense clumps mapped using the 850μm continuum emission by the ATLASGAL survey. A total of 18 variable sources are centered on the submillimeter clump peaks and coincide (<1″) with a 24μm point or compact (<10″) source. Of these 18 sources, 13 can be fit by YSO models. The 13 variable YSOs (VYSOs) have luminosities of ∼10 3 L e , an average mass of 8M e , and a range of ages up to 10 6 yr. A total of 11 of these 13 VYSOs are located in the midst of infrared dark clouds. Nine of the 13 sources have ΔK>2 mag, significantly higher compared to the mean variability of the entire VVV sample. The light curves of these objects sampled between 2010 and 2015 display rising, declining, or quasi-periodic behavior but no clear periodicity. Light-curve analysis using the Plavchan method shows that the most prominent phased signals have periods of a few hundred days. The nature and timescale of variations found in 6.7 Ghz methanol maser emission in massive stars are similar to that of the VYSO light curves. We argue that the origin of the observed variability is episodic accretion. We suggest that the timescale of a few hundred days may represent the frequency at which a spiraling disk feeds dense gas to the young massive star.

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Models of class II methanol masers based on improved molecular data

Cited by 280 publications

References 38 publications

12.2-GHz methanol maser MMB follow-up catalogue – IV. Longitude range 20°–60°

12.2-GHz methanol maser MMB follow-up catalogue – IV. Longitude range 20°–60°

The 6-GHz Multibeam Maser Survey – III. Comparison between the MMB and HOPS

Highly Variable Young Massive Stars in Atlasgal Clumps

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