'Most luminous galaxy' in the universe is ripping itself apart

The galaxy is "a beast in the infrared," said lead researcher Roberto Assef.

By Brooks Hays
'Most luminous galaxy' in the universe is ripping itself apart
An artistic rendering of W2246-0526, an obscured quasar galaxy whose intense brightness is hidden by a wall of dust. Photo by Dana Berry/SkyWorks and ALMA/ESO/NAOJ/NRAO

SANTIAGO, Chile, Jan. 15 (UPI) -- Researchers recently discovered the universe's "most luminous galaxy" to be one of the most violently turbulent. "So chaotic that it is ripping itself apart," said astronomer Tanio Diaz-Santos.

"Most luminous galaxy" is in quotation marks because almost no visible light escapes the boundaries of the galaxy, dubbed W2246-0526.


Researchers have been using the Atacama Large Millimeter/submillimeter Array, or ALMA, to document for the first time the movement of the galaxy's interstellar material.

Its intense luminosity is absorbed by a thick surrounding wall of dust, which re-emits the energy at infrared wavelengths. The galaxy's infrared glow is the equivalent of 350 trillion suns. Scientists call this type of galaxy an "obscured quasar."

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But the galaxy is so unusually bright, it's found its way into an even rarer category -- a member of an exclusive group of Hot, Dust-Obscured Galaxies or Hot DOGs. Roughly 1 in every 3,000 quasars found by astronomers is a Hot DOG.

W2246-0526 derives its energy from a supermassive black hole at its center. Surrounding the black hole is a high-energy accretion disk where gas spirals are condensed and superheated.

"These properties make this object a beast in the infrared," Roberto Assef, an astronomer and colleague of Diaz-Santos at the Universidad Diego Portales, said in a press release.

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NASA's Wide-field Infrared Survey Explorer spacecraft, or WISE, first alerted scientists to the galaxy's spectacular brightness. Now ALMA has revealed the conditions of the engine room.

"The powerful infrared energy emitted by the dust then has a direct and violent impact on the entire galaxy, producing extreme turbulence throughout the interstellar medium," added Assef, leader of the ALMA observing team.

Assef and his research team believe the galaxy's days as the most luminous are numbered.

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The quasar's interstellar gas is streaming at high speeds in all directions, excited by the intense energy of its supermassive black hole.

"Large amounts of ionized carbon were found in an extremely turbulent dynamic state throughout the galaxy," Diaz-Santos said.

The researchers liken the galaxy to a pot of boiling water. Eventually, they say, the galaxy will boil away all of its star-forming material.

"If this pattern continues, it is possible that in the future W2246 ends up shedding a large part of the gas and dust it contains," said astronomer Manuel Aravena. "Only ALMA, with its unparalleled resolution, can allow us to see this object in high definition and fathom such an important episode in the life of this galaxy."

The uniquely bright and violent galaxy is described in a new paper, published in the Astrophysical Journal Letters.


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