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Universe's most luminous galaxy is ripping itself apart

January 19, 2016 15:18 IST

The most luminous galaxy in the universe -- a so-called obscured quasar 12.4 billion light-years away -- is so violently turbulent that it may eventually jettison its entire supply of star-forming gas, a new study has found.

A team of researchers used ALMA (Atacama Large Millimetre/submillimetre Array) to trace, for the first time, the actual motion of the galaxy's interstellar medium -- the gas and dust between the stars.

They found a galaxy "so chaotic that it is ripping itself apart," according to Tanio Diaz-Santos from the DiegoPortalesUniversity in Chile.

Previous studies with NASA's Wide-field Infrared Survey Explorer spacecraft showed that the galaxy, dubbed W2246-0526, is glowing in infrared light as intensely as approximately 350 trillion Suns.

Evidence strongly suggests that this galaxy is an obscured quasar, a very distant galaxy with a voraciously feeding supermassive black hole at its centre that is completely obscured behind a thick blanket of dust, researchers said.

This galaxy's startling brightness is powered by a tiny, yet incredibly energetic disk of gas that is being superheated as it spirals in on the supermassive black hole.

The light from this blazingly bright accretion disk is then absorbed by the surrounding dust, which re-emits the energy as infrared light, they said.

"These properties make this object a beast in the infrared," said Roberto Assef from UDP.

"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," he added.

The astronomers compared this turbulent action to a pot of boiling water. If these conditions continue, the galaxy's intense infrared radiation will boil away all of its interstellar gas, they said.

This galaxy belongs to a very unusual type of quasar known as Hot, Dust-Obscured Galaxies or Hot DOGs. These objects are very rare; only 1 out of every 3,000 quasars observed by WISE belongs to this class.

The astronomers used ALMA to precisely map the motion of ionised carbon atoms throughout the entire galaxy. These atoms, which are tracers for interstellar gas, naturally emit infrared light, which becomes shifted to millimetre wavelengths as it travels the vast cosmic distances to Earth due to the expansion of the universe.

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

The data shows that this interstellar material is careening anywhere from 500 to 600 kilometres per second throughout the entire galaxy, researchers said.

The findings will be published in the journal Astrophysical Journal Letters.

Image: This artist's rendering shows a galaxy called W2246-0526, the most luminous galaxy known. New research suggests there is turbulent gas across its entirety, the first example of its kind. Photograph: NRAO/AUI/NSF; Dana Berry / SkyWorks; ALMA (ESO/NAOJ/NRAO)

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