Constraining the properties of 1.2-mm dust clumps that contain luminous
  water masers
  We have conducted a sensitive water maser search with the ATCA towards 267
1.2-mm dust clumps presented in the literature. We combine our new observations
with previous water maser observations to extend our sample to 294 1.2-mm dust
clumps, towards which we detect 165 distinct water maser sites towards 128
1.2-mm dust clumps. Within the fields of our observations, we additionally find
four water masers with no apparent associated 1.2-mm dust continuum emission.
Our overall detection rate of 44 per cent appears to vary as a function of
Galactic longitude. We find that there is an excellent correspondence between
the locations of the detected water masers with the peak of the target 1.2-mm
dust clump sources. As expected from previous similar studies, the water masers
are chiefly detected towards the bigger, brighter and more massive 1.2-mm dust
clumps. We find further evidence that the water masers tend to increase in flux
density (and therefore luminosity), as well as velocity range, as the sources
evolve. We also show that the current sample of water maser sources suffer less
from evolutionary biases than previous targeted searches. A higher fraction of
dust clump sources in our sample are only associated with water masers (41)
than only associated with methanol masers (13). This suggests that water masers
can be present at an even earlier evolutionary stage than 6.7-GHz methanol
masers. Comparison of the water maser detection rates associated with different
combinations of methanol maser and radio continuum, as well as those with
neither tracer, shows that the highest detection rate is towards those sources
which also exhibit methanol maser emission. We have tested a previously
hypothesised model for water maser presence towards 1.2-mm dust clumps. We
suggest refinements and future work which will further constrain the nature of
the driving sources associated with water masers.
