A search for water masers associated with class II methanol masers – I. Longitude range 6°–20°

Mon. Not. R. Astron. Soc.

et al. 2016

Self Cite

This is the second paper in a series of catalogues of 22-GHz water maser observations towards the 6.7-GHz methanol masers from the Methanol Multibeam (MMB) Survey. In this paper we present our water maser observations made with the Australia Telescope Compact Array towards the masers from the MMB survey between l = 341 • through the Galactic centre to l = 6 • . Of the 204 6.7-GHz methanol masers in this longitude range we found 101 to have associated water maser emission (∼ 50 per cent). We found no difference in the 6.7-GHz methanol maser luminosities of those with and without water masers. In sources where both maser species are observed, the luminosities of the methanol and water masers are weakly correlated. Studying the mid-infrared colours from GLIMPSE we found no differences between the colours of those sources associated with both methanol and water masers and those associated with just methanol. Comparing the column density and dust mass calculated from the 870-µm thermal dust emission observed by ATLASGAL, we found no differences between those sources associated with both water and methanol masers and those with methanol only. Since water masers are collisionally pumped and often show emission further away from their accompanying YSO than the radiatively pumped 6.7-GHz methanol masers, it is likely water masers are not as tightly correlated to the evolution of the parent YSO and so do not trace such a well defined evolutionary state as 6.7-GHz methanol masers.

Section: Resultsmentioning

confidence: 98%

“…The observing strategy for the water maser follow-up of the MMB survey is described in detail in Titmarsh et al (2014). Here we only repeat the essential details.…”

Section: Observations and Data Reductionmentioning

confidence: 99%

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A search for water masers associated with class II methanol masers – II. Longitude range 341° to 6°

Titmarsh

Mon. Not. R. Astron. Soc.

et al. 2016

Self Cite

“…Across the full MMB range, the median velocity of 6.7-GHz methanol masers is 6 km s −1 (Green et al 2017) and the median of 12.2-GHz sources is 1.7 km s −1 and therefore are consistent with the sub-sample we consider here. The fact that the water masers show the largest velocity range is expected, particularly because of their tendency to trace high-velocity outflow, but the median velocity of the HOPS sources is significantly lower than either of the Breen et al (2010b) or Titmarsh et al (2014Titmarsh et al ( , 2016 targeted water maser observations which have medians of 15 and 17 km s −1 , respectively. A part of this difference can be accounted for by the fact that the Walsh et al (2014) quoted peak velocities of spots and therefore results in an underestimation of the velocity ranges of sites, but some of the difference is due to the unbiased nature of HOPS.…”

Section: Basic Properties Of the Different Maser Populationsmentioning

confidence: 88%

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

Contreras

Monthly Notices of the Royal Astronomical Society

et al. 2017

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.

“…We have also shown that, like their 6.7-GHz methanol maser counterparts, the 12.2-GHz maser emission tends to increase in luminosity with evolution. The third instalment of this catalogue series ) allowed us to compare our complete 6.7-and 12.2-GHz methanol maser sample with the results of water maser observations targeted towards the same sample (Titmarsh et al 2014). While we found that water masers were more likely to be present alongside more evolved methanol maser sources, it was evident that the evolutionary implications of this were not straight forward.…”

Section: Discussionmentioning

confidence: 99%

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

Mon. Not. R. Astron. Soc.

Caswell

et al. 2016

Self Cite

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.