DWINGELOO, NETHERLANDS – Astronomers have found signs of water about 20 billion light years away – further than ever before.
The water vapour is believed to be contained in a jet ejected from a supermassive black hole at the centre of a galaxy named MG J0414+0534. It is seen as a maser, whereby molecules in the gas amplify and emit beams of microwave radiation in much the same way as a laser emits beams of light.
The faint signal is only detectable by using a technique called gravitational lensing, where the gravity of a massive galaxy in the foreground acts as a cosmic telescope, bending and magnifying light from the distant galaxy to make a clover-leaf pattern of four images of MG J0414+0534.
Dr John McKean of the Netherlands Institute for Radio Astronomy (ASTRON) said, “We have been observing the water maser every month since the detection and seen a steady signal with no apparent change in the velocity of the water vapour in the data we’ve obtained so far. This backs up our prediction that the water is found in the jet from the supermassive black hole, rather than the rotating disc of gas that surrounds it.”
The radiation from the water maser was emitted when the universe was only about 2.5 billion years old, a fifth of its current age. It is about 19.8 billion light years away.
The team believes there are likely to be many more similar systems in the early universe. Surveys of nearby galaxies have found that only about five percent have powerful water masers associated with active galactic nuclei, and that very powerful water masers are much rarer than their less luminous counterparts.
“From what we know about the abundance of water masers locally, we could calculate the probability of finding a water maser as powerful as the one in MG J0414+0534 to be one in a million from a single observation. This means that the abundance of powerful water masers must be much higher in the distant universe than found locally, because I’m sure we are just not that lucky!” said Dr McKean.
The discovery was made by a team led by Dr Violette Impellizzeri using the 100m Effelsberg radio telescope in Germany, and was confirmed by observations with the Expanded Very Large Array in the US.
The team is now analysing high-resolution data to find out how close the water maser lies to the supermassive black hole, which will give them new insights into the structure at the centre of active galaxies in the early universe.
“This detection of water in the early universe may mean that there is a higher abundance of dust and gas around the super-massive black hole at these epochs, or it may be because the black holes are more active, leading to the emission of more powerful jets that can stimulate the emission of water masers,” said Dr McKean.