Fierce winds stifle the birth of a star in a distant galaxy

Astronomers using ALMA, using a gravitational lens, have detected the galactic "wind" furthest away from the molecules ever observed, whereas the universe had only 1 billion d & rsquo; # 39; years. By tracing the outgoing flow of hydroxyl (OH) molecules – which announce the presence of star-forming gases in galaxies – researchers show how some galaxies of the early universe have extinguished a continuous bonfire of the birth of stars.

Some galaxies, such as the Milky Way and Andromeda, have relatively low and measured birth velocities, with about a new star that ignites each year.

Other galaxies, known as star-shaped galaxies, forge hundreds or even thousands of stars every year. This frantic pace can not, however, be maintained indefinitely.

To avoid burning in a flash of ephemeral life, some galaxies strangle their sleepy birth by ejecting – at least temporarily – vast reserves of gas into their expansive halos, where gas escapes totally or slowly falls on the galaxy. , triggering future bursts of star formation.

Until now, however, astronomers have not been able to directly observe these powerful flows in the very early universe, where such mechanisms are essential to prevent galaxies from becoming too big and too fast.

New observations with Atacama's large millimeter / submillimeter network (ALMA) show – for the first time – a powerful galactic "wind" of molecules in a galaxy, while the universe was only a billion years old. This result gives a glimpse of how some galaxies of the primitive universe were able to self-regulate their growth in order to continue forming stars in cosmic time.

"Galaxies are complicated and disordered beasts, and we believe that exits and winds are critical elements in their formation and evolution, regulating their ability to grow," said University astronomer Justin Spilker. from Texas appearing in the newspaper Science.

Astronomers have observed winds of the same size, speed, and mass in nearby star galaxies, but the new ALMA observation is the most distant, unambiguous exit ever seen in the primitive universe.

The galaxy, known as SPT2319-55, is more than 12 billion light-years away. It was discovered by the South Pole Telescope of the National Science Foundation.

ALMA was able to observe this object at such a considerable distance using a gravitational lens provided by another galaxy located along the line of sight between the Earth and SPT2319-55. Gravitational lenses – the bending of light due to gravity – enlarges the galaxy's background to make it brighter, allowing astronomers to observe it in more detail than they could do it differently. Astronomers use specialized computer programs to "untangle" the effects of the gravitational lens in order to reconstruct an accurate image of the more distant object.

This lens-assisted view revealed a powerful "wind" of gas forming stars coming out of the galaxy at nearly 800 kilometers per second. Instead of a light and steady breeze, the wind flies into discrete tufts, eliminating star-forming gas as quickly as the galaxy can turn this gas into new stars.

The flow was detected by the signature in millimeters of a molecule called hydroxyl (OH), which appeared as an absorption line: essentially, the shadow of an OH impression in the bright infrared light of the galaxy.

As new dust-enveloped stars form, this dust heats up and shines brightly in the infrared light. But the galaxy also launches a wind and a part blows in our direction. As the infrared light crosses the wind during its journey to the Earth, the OH molecules in the wind absorb some of the infrared light at a very particular wavelength that the ALMA can observe. .

"This is the absorption signature that we have detected, and from there we can also know how fast the wind is moving and have a rough idea of ​​how much material is in the outlet," Spilker said. . ALMA is able to detect this infrared light as it has been extended to millimeter wavelengths during its journey to Earth by the continued expansion of the Universe.

Molecular winds are an effective way for galaxies to self-regulate their growth, the researchers note. These winds are probably triggered either by the combined effect of all the supernova explosions that accompany the rapid and massive formation of stars, or by a powerful release of energy because part of the gas in the galaxy falls on the supermassive black hole in the center. .

"Until now, we have observed only one galaxy at such a remarkable cosmic distance, but we would like to know if such winds are also present in other galaxies to see at how common they are, "concluded Spilker. "If they occur essentially in every galaxy, we know that molecular winds are both ubiquitous and a very common way for galaxies to self-regulate their growth."

"This ALMA observation shows how nature, coupled with exquisite technology, can give us insight into distant astronomical objects," said Joe Pesce, director of the NSF program for NRAO / ALMA. spectral characteristic of this important molecule. "