The brightest galaxy eats its neighbors

The impression of this artist shows the galaxy WISE J224607.55-052634.9, the most luminous galaxy ever discovered. A new study using data from the Atacama Large Millimeter / Subillimeter Array (ALMA) shows that this galaxy traps dust and other materials from three of its smaller galactic neighbors. (NRAO / AUI / NSF) S. Dagnello

According to a new study published in the journal Science and co-authored by scientists at NASA's Jet Propulsion Laboratory in Pasadena, California, the brightest galaxy ever discovered is cannibalism not one or two but from at least three of its smaller neighbors. The study shows that the material that the galaxy flies from its neighbors probably contributes to its very high brightness.

Discovered by NASA's Wide Field Field Infrared Survey Explorer (WISE) in 2015, this galaxy, dubbed WISE J224607.55-052634.9, is by no means the largest or most massive galaxy to our knowledge, but it radiates 350,000 billion times. the brightness of the sun If all galaxies were placed equidistant from us, WISE J224607.55-052634.9 (or W2246-0526 abbreviated) would be the brightest.

New observations using the Atacama Large Millimeter / Atacama (ALMA) lattice in Chile reveal distinct dust trails from three small galaxies near W2246-0526. The tracks contain about as much material as the small galaxies themselves, and it is not clear whether these galaxies will escape their current fate or be completely consumed by their bright neighbor.

The record brightness of the W2246-0526 is not only from stars, but also from a collection of hot gases and dust concentrated around the center of the galaxy. At the heart of this cloud is a supermassive black hole, recently determined to be 4 billion times more massive than the Sun. Under the effect of intense gravity, the material falls at high speed toward the black hole. It crushes and heats up to millions of degrees. The material shines with incredible brilliance. Galaxies containing these types of light structures powered by black holes are called quasars.

Like any engine on Earth, the enormous fuel efficiency of the W2246-0526 requires equally high fuel consumption. In this case, it means that the gas and dust form stars and reconstruct the cloud around the central black hole. The new study shows that the amount of material accumulated by its neighbors by WJ2246-0526 is sufficient to replenish what is consumed, thus maintaining the exceptional luminosity of the galaxy.

"It is possible that this binge eating has already been going on for some time, and we expect the galactic feast to continue for at least a few hundred million years," said Tanio Diaz-Santos of the Universidad Diego Portales in Santiago, Chile. author of the study.

This image, created using radio data from Atacama's large millimeter / submillimeter (ALMA) data network, shows W2246-0526 whistling away from three small galaxies. W2246-0526 and one of his companions are in the center; the second galaxy is above them; the third is on the lower left. Image credit: ALMA (ESO / NAOJ / NRAO); S. Dagnello (NRAO / AUI / NSF)

In the new study, scientists used images from ALMA – a collection of individual radio antennas working together as a single telescope – to identify traces of dusty matter. The position of the accretion streaks strongly suggests that they contain material flowing between W2246-0526 and other galaxies. In addition, the trails have the right morphology – in other words, their shape is consistent with the way the material should flow if it is pulled from one galaxy to another .

This type of galactic cannibalism is not uncommon. Astronomers have already observed galaxies merging with or neighboring neighboring materials of the nearby universe. For example, the pair of galaxies known collectively as "mice" has this name because each has a long, thin tail of growing material that moves away from it.

W2246-0526 is the most distant galaxy that has ever been found to accumulate material from multiple sources. The light of W2246-0526 took 12.4 billion years to reach us. Astronomers see the object as it was when our universe was only one tenth of its current age of 13.8 billion years. At this distance, material flows that fall into W2246-0526 are particularly weak and difficult to detect. The study is based on 2.5 hours of observation with 40 parabolic dishes of 12 meters of ALMA.

"We knew from previous data that there were three galaxies companions, but there was no evidence of interactions between these neighbors and the central source," Diaz-Santos said. "We were not looking for cannibalistic behavior and we were not expecting it, but this deep dive with the ALMA observatory shows it very clearly."

W2246-0526 belongs to a particular category of particularly bright quasars, known as hot galaxies hidden by dust or Hot DOGs. Astronomers believe that most quasars draw some of their fuel from external sources. One possibility is that these objects receive a trickle of slow material from the space between the galaxies. Another is that they feed in bursts while eating other galaxies, which seems to occur with W2246-0526. It is unclear whether W2246-0526 is representative of other darkened quasars (those whose central engines are obscured by thick dust clouds) or whether it is a separate case.

"This galaxy is perhaps unique because it is almost twice as bright as any other galaxy found with WISE and formed very early in the history of the universe", said Peter Eisenhardt, JPL project scientist for WISE and co-author of the new paper. "But we have discovered many other galaxies with WISE similar to this one: far away, dusty and thousands of times brighter than typical galaxies nowadays. So with W2246-0526, we can see what happens during a key step in the evolution of darkened galaxies and quasars. "

In the end, the gluttony of the galaxy can only lead to self-destruction. Scientists assume that obscured quasars that collect too much material eventually vomit gas and dust across the galaxy. This onslaught of material halts the formation of new stars, essentially pushing the galaxy into retirement while other galaxies continue to renew themselves with the birth of new stars.

A complementary study of W2246-0526, published November 14 in Astrophysical Journal, provided the mass measurement of the supermassive black hole located at the center of the galaxy – 4 billion times the mass of the Sun. This mass is important, but the extreme brightness of W2246-0526 would have required a supermassive black hole of a mass at least three times higher, according to the authors of the article. Resolving this apparent contradiction will require more observations.