| Luminous water masers (22.235 GHz rest-frame) are associated with the parsec-scale environment around supermassive black holes at the centres of Active Galactic Nuclei. These maser lines can be used to measure the mass of the central black hole, determine an accurate distance to the host galaxy and be used to study the outflows that we see as radio-jets. Therefore, water maser lines are very useful when it comes to understanding the properties of the most powerful objects in the Universe.
The most distant object that water has been detected in thus far is the gravitationally lensed quasar MG J0414+0534 at redshift 2.639. To determine the source of the water maser emission, a monitoring campaign has been carried out with the 305-m Arecibo telescope in Puerto Rico. The fantastic sensitivity provided by Arecibo has given us the most detailed spectrum yet of the maser lines, showing that the line structure has at least three components at different velocities (left panel). The 15 month monitoring period found that the line is fairly stable in velocity and intensity (right panel), leading to the conclusion that the water vapour is associated with the radio-jets of the quasar. High resolution very long baseline interferometry data are being analyzed to confirm this conclusion.
The results from the Arecibo monitoring of the MG J0414+0534 water maser were reported by Castangia, Impellizzeri, McKean et al. (2011, A&A, 529, A150).
A survey for water masers from ~25 other gravitationally lensed quasars is now being carried out with Arecibo. The results of this new survey will be released soon.