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The ALMA, aided by a gravitational lens, pictured the flight, or "wind," of a galaxy seen when the universe was only 1 billion years old. The ALMA image (call circle) indicates the location of the hydroxyl (OH) molecules. These molecules trace the location of the gas in star formation as it flees the galaxy, driven by supernovae or a "wind" propelled by a black hole. The background star field (Blanco Telescope Dark Energy Survey) shows the location of the galaxy. The circular and double lobe shape of the far galaxy is due to the distortion caused by the cosmic magnifying effect of an intermediate galaxy. Credit: ALMA (ESO / NAOJ / NRAO), J. Spilker / UT-Austin; NRAO / AUI / NSF, S. Dagnello; AURA / NSF
For the first time, a powerful "wind" of molecules has been detected in a galaxy 12 billion light years away. At a time when the universe was less than 10% of its current age, University of Texas research in Austin, Justin Spilker, sheds light on how early galaxies regulated the birth of stars to not to disperse. The research will appear in the September 7 issue of the journal Science.
"Galaxies are complicated and disordered beasts, and we believe that exits and winds are critical elements of how they form and evolve, regulating their ability to grow," said Spilker.
Some galaxies such as the Milky Way and Andromeda have relatively low and measured birth velocities, with about a new star lit each year. Other galaxies, known as star galaxies, forge hundreds or even thousands of stars each 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, astronomers have been unable 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.
Spilker's observations with the large Atacama millimeter / submillimeter array (ALMA) show, for the first time, a powerful galactic wind of molecules in a galaxy, while the universe only had 1 billion years. 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.
Astronomers have observed winds of the same size, velocity, and mass in nearby star galaxies, but the new ALMA sighting is the furthest outflow ever observed in the early universe.
An artist impression of a molecular gas outlet of an active galaxy forming stars. Credit: NRAO / AUI / NSF, D. Berry
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. The gravitational lens – the curvature of light due to gravity – enlarges the galaxy's background to make it brighter, allowing astronomers to observe it in more detail than they do. could do it differently. Astronomers use specialized computer programs to decipher the effects of gravitational lenses 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 output stream was detected by the millimeter – wave signature of a molecule called hydroxyl (OH), which appears as a line of absorption: essentially, the shadow of the molecule. an OH impression in the bright infrared light of the galaxy.
Molecular winds are an effective way for galaxies to self-regulate their growth, the researchers note. These winds are probably triggered by the combined effects 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 at its 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 primarily in every galaxy, we know that molecular winds are both ubiquitous and a very common way for galaxies to self-regulate their growth."
This research is presented in an article entitled "Rapid molecular evolution of a galaxy forming a dusty star in the primitive universe", by J.S. Spilker et al. in the newspaper Science.
Explore more:
Image: Hubble galaxy cluster abundance horn
More information:
J.S. Spilker et al., "Rapid Molecular Flow of a Galaxy in Dusting Star Formation at the Beginning of the Universe" Science (2018). science.sciencemag.org/cgi/doi… 1126 / science.aap8900
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