A search for water masers associated with class II methanol masers – II. Longitude range 341° to 6°
Titmarsh, AM and Ellingsen, SP and Breen, SL and Caswell, JL and Voronkov, MA, A search for water masers associated with class II methanol masers - II. Longitude range 341° to 6°, Monthly Notices of the Royal Astronomical Society, 459, (1) pp. 157-170. ISSN 0035-8711 (2016) [Refereed Article]
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 (Galactic Legacy Infrared Midplane Survey Extraordinaire), 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 (APEX Telescope Large Area Survey of the GALaxy), 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 young stellar object (YSO) than the radiatively pumped 6.7-GHz methanol masers, it is likely that 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.