Galaxies in the early universe quenched wildfire of starbirth

The ALMA image (circled and enlarged) shows the location of hydroxyl (OH) molecules. The background star field (Blanco Telescope Dark Energy Survey) shows the location of the galaxy. | Credit: ALMA (ESO/NAOJ/NRAO), Spilker; NRAO/AUI/NSF, S. Dagnello; AURA/NSF

Astronomers, using ALMA, with the help of a gravitational lens, have detected the most-distant galactic “wind” of molecules that has ever been observed, seen when the universe was only one billion years old. By following the outflow of hydroxyl (OH) molecules – which advertises the presence of star-forming gas in galaxies – the research team shows how some galaxies in the early universe had quenched an ongoing wildfire of starbirth. Some galaxies, like the Milky Way and Andromeda, have comparatively slower and measured rates of starbirth, with only about one new star igniting each year.

Other galaxies, which are known as starburst galaxies, can give birth to 100s or even 1000s of stars every year. But this pace, however, cannot be maintained indefinitely, and to avoid burning out quickly, some of these galaxies inhibit back their runaway starbirth by letting out – even for a small time – large stores of gas out into their expansive halos, where the gas either escapes totally or starts to slowly rain back in on the galaxy, which triggers future blasts of star formation.

Though up until now, astronomers haven’t been able to directly monitor these strong, powerful outflows in the very early universe, in which such mechanisms are vital to stop galaxies from growing too big or too fast.

New observations with the Atacama Large Millimeter/submillimeter Array (ALMA), have shown– for the very first time — a strong, fierce galactic “wind” of molecules in a galaxy seen when the universe was only one billion years old. This gives new insights into how certain galaxies in the early universe had the ability to self-regulating their growth so they could keep on forming stars across cosmic time.

“Galaxies are complicated, messy beasts, and we think outflows and winds are critical pieces to how they form and evolve, regulating their ability to grow,” said Justin Spilker, who is an astronomer at the University of Texas at Austin and lead author on a paper appearing in the journal Science.

ALMA was able to achieve these staggering results such tremendous distance with the help of a gravitational lens provided by a different galaxy that is situated on almost exactly along the line of sight between Earth and SPT2319-55. Gravitational lensing – which is the bending of light due to gravity — magnifies the galaxy in the background to make it look brighter, which lets the astronomers to study it in depth- which they wouldn’t otherwise be able to.


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