H2O masers are found in about 7% of Type 2 objects in the local universe. They provide information on the nuclear
tori and black hole masses of AGNs and have, in one case, been used to make a precise measurement of the distance
to an external galaxy (NGC 4258) independent of the usual distance ladder. We have discovered a water maser
in the distant universe, from a type 2 quasar at z = 0:66. This is more than an order of magnitude farther away
than previously known megamasers. While the spectrum of this object contains but a single spike (at the sensitivity
achieved), and thus is not a direct analogue of NGC 4258, its signicance lies in part in opening up the possibility of
nding an object at high-z that can be used to test deviations from the Hubble law inferred from Type Ia supernovae.
In this proposal we request time to image this new and unique object, to help determine or constrain the properties
of masers in the distant universe, and to test the feasibility of future VLBI on newly discovered weak maser sources. |