W2246-0526 is the most luminous galaxy in the universe. It is an object shrouded in dust and shines with the light of more than 300 trillion Suns. But, this galaxy is not just a record-breaker, it is also a thief. It has been caught red-handed funneling gas from other galaxies towards its supermassive black hole.
As reported in Science, an international team of astronomers looked at the galaxy and its surroundings and discovered bridges of material from three galaxy companions, all with dusty material. These multiple mergers are responsible for the obscuring dust that surrounds W2246-0526 and for its incredibly active supermassive black hole, which is being fed this stolen gas.
The system is also undergoing a major episode of star formation with tens of thousands of new stars being formed every year. This abundance of new stars contributes to the luminosity of the object, heating up the gas so much that it shines brightly in infrared light. W2246-0526 may be only one of the 20 Extremely Luminous Infrared Galaxies (ELIRGs), but it's by far the brightest.
These important observations were only possible thanks to the Atacama Large Millimeter/submillimeter Array (ALMA), which was capable of imaging the cold gas moving in intergalactic space and into W2246-0526. The three companions are known as C1, C2, and C3. C1 and C3 have stable bridges of material connecting them to the main galaxy. C2 is more distant and shows a “tidal tail,” a stream of gas and dust, which can form as two galaxies pass near each other.
"The ALMA images are important because after trying to understand extremely powerful galaxies like W2246 since we discovered them with the WISE satellite in 2010, we can now see some real details about how they get to boost their power to about 10,000 times that of our Milky Way," co-author Professor Andrew Blain, from the University of Leicester, said in a statement.
The team had suspected mergers to be behind such a bright galaxy for a while, but without these observations, there was no evidence confirming the link. This paper finally confirms that mergers are a key evolutionary step in the brightest galaxies in the universe by providing the gas to fuel stars and the supermassive black hole and the dust to shroud them.