Cosmic collision spells beginning of the end

Astronomers witness possible new mechanism for galaxies to die.

Astronomers may have witnessed a new way for galaxies to “die”, using the super-sensitive Atacama Large Millimeter/submillimeter Array (ALMA) in Chile.

The array watched as a galaxy nine billion light-years away ejected nearly half of its star-forming gas into space.

The astronomers suspect this cataclysmic event was triggered by two galaxies colliding and merging to form a new one – inspiringly called ID2299. The research appears in Nature Astronomy.

“This is the first time we have observed a typical massive star-forming galaxy in the distant universe about to ‘die’ because of a massive cold gas ejection,” says lead researcher Annagrazia Puglisi, from Durham University,

UK, and the Saclay Nuclear Research Centre (Cea-saclay) in France.

Previous evidence has indicated that such ejections can be caused by high-speed galactic winds blasted out from newly formed massive stars, or the powerful activity of black holes spinning at the hearts of massive galaxies.

“Our study suggests that gas ejections can be produced by mergers,” says co-author Emanuele Daddi, of Cea-saclay.

The clue that led to this conclusion came from a “tidal tail” – an elongated stream of stars and gas extending out into interstellar space. Usually, these features are faint, but the team managed to capture ID2299’S when it was just launching into space and still relatively bright.