Brightest-known galaxy is cannibalizing its three neighbors
If the extremely faint, nearby "ghost" galaxy Antlia 2 had an exact opposite, it would be W2246-0526. This galaxy sits 12.4 billion light-years from Earth – almost the entire radius of the observable universe – and is the most luminous galaxy ever discovered, with the brightness of 350 trillion Suns. Now, astronomers have found that W2246-0526 is cannibalizing three neighboring galaxies.
As suggested by its full name – WISE J224607.55-052634.9 – the galaxy was discovered by NASA's Wide-field Infrared Survey Explorer (WISE) in 2015. Its incredible luminosity isn't just the result of its stars though: W2246-0526 is shrouded in dust and gas, which is being swallowed up by the supermassive black hole at its core. As that matter speeds up and heats up, it shines bright as a quasar, giving it the dubious name of a Hot, Dust-Obscured Galaxy (Hot DOG).
"This galaxy may be one of a kind, because it's nearly twice as luminous as any other galaxy we've found with WISE and it formed very early in the universe's history," says Peter Eisenhardt, co-author on the new paper. "But we've discovered many other galaxies with WISE that are similar to this one: distant, dusty and thousands of times more luminous than typical galaxies are today. So with W2246-0526, we may be seeing what goes on during a key stage in the evolution of galaxies and obscured quasars."
Given its quirky nature, astronomers have continued to observe W2246-0526, and in 2016 it was found that it may be tearing itself apart. The latest study observed the galaxy for 2.5 hours using 40 of the huge radio dishes at the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile.
Those observations revealed faint but distinct dust trails feeding into W2246-0526 from three nearby galaxies. That theft appears to be behind the quasar's ability to keep burning so bright, as the matter it steals from its neighbors replenishes that consumed by the black hole.
"It is possible that this feeding frenzy has already been ongoing for some time, and we expect the galactic feast to continue for at least a few hundred million years," says Tanio Diaz-Santos, lead author of the study.
A companion study looked at the supermassive black hole at the center of the quasar. Using optical and near-infrared spectroscopy, the team found that its mass is about four billion times that of the Sun. Large as that sounds, it's only about a third of what was expected, so further observations are required to determine why that is the case.
Source: JPL NASA