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Detection of a water maser defies the odds

Scientists working in Germany and Italy have detected an extremely luminous water maser — the microwave equivalent of a laser — farther from our galaxy than ever reported previously. Water masers are associated with the so-called supermassive black holes at the centers of active galaxies.

Based on knowledge of relatively local masers, the probability of finding a highly luminous water maser associated with a single active galaxy was expected to be one in a million. As reported in Nature this week, this maser is twice as luminous as the most powerful local water maser and half as luminous as the most distant maser previously known.

Violette Impellizzeri from the Max-Planck-Institut für Radioastronomie in Bonn and colleagues used gravitational lensing — where the gravity of a massive object bends light from a more distant one to create an enhanced image — to increase their chances of finding water masers in active galaxies. Using the Effelsberg radio telescope and the Expanded Very Larger Array (EVLA) in the latter half of 2007, they made their surprising observations at redshift 2.64 in the dust- and gas-rich type-1 quasar called MG J0414+0534.

According to the scientists, spotting such a maser in the first galaxy they observed must mean that the volume densities and luminosities of masers are higher at redshift 2.64.

Nature 456, 7224 table of contents

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