2014MNRAS.444..217U

We present simultaneous observations of H2O maser emission and radio continuum at 1.3 cm carried out with the Australia Telescope Compact Array towards two sources, IRAS 16333-4807 and IRAS 12405-6219, catalogued as planetary nebula (PN) candidates, and where single-dish detections of H2O masers have been previously reported. Our goal was to unambiguously confirm the spatial association of the H2O masers with these two PN candidates. We detected and mapped H2O maser emission in both fields, but only in IRAS 16333-4807 the maser emission is spatially associated with the radio continuum emission. The properties of IRAS 16333-4807 provide strong support for the PN nature of the object, hereby confirming it as the fifth known case of an H2O maser-emitting PN. This source is bipolar, like the other four known H2O maser-emitting PNe, indicating that these sources might pertain to a usual, but short phase in the evolution of bipolar PNe. In IRAS 12405-6219, the H2O maser and radio continuum emission are not associated with each other and, in addition, the available data indicate that this source is an H ii region rather than a PN.