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Posted on 7 Sep 2018
"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 astronomer Justin Spilker of the University of Texas.
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, the University of Texas-Austin study, Justin Spilker, sheds light on how early galaxies regulated the birth of stars for do not blow yourself up. The research will appear in the Sept. 7 issue of the journal Science.
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, called star galaxies (see the antenna galaxies above), 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 Atacama's large millimeter / submillimeter array (ALMA) show – for the first time – a powerful galactic wind of molecules in a galaxy, while the universe was only 1 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.
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.
The ALMA image (call circle) indicates the location of the hydroxyl (OH) molecules. These molecules trace the location of the gas in star formation when it flees the galaxy, driven by supernovae or a "wind" fed by black holes. The field of dark stars (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.
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 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 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.
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 essentially in every galaxy, we know that molecular winds are both ubiquitous and a very common way for galaxies to self-regulate their growth."
The image of NASA's Hubble Space Telescope of the top antenna galaxies is the clearest of this pair of galaxies. During the collision, billions of stars will be formed. The brightest and most compact regions of these native star regions are called super bunches of stars.
The two spiral galaxies began interacting a few hundred million years ago, making Antennas galaxies one of the closest and youngest examples of a pair of galaxies colliding. Nearly half of the weak antenna image objects are young bunches containing tens of thousands of stars. The orange spots to the left and right of the center of the image are the two nuclei of the original galaxies and consist mainly of old stars crossed by filaments of dust, which appear brown on the image. Both galaxies are dotted with bright blue areas surrounded by gaseous stars, appearing in the pink image.
The new image allows astronomers to better distinguish stars and super-clusters of stars created during the collision of two spiral galaxies. As the clusters of the image get older, astronomers are discovering that only about 10% of the newly formed star supergrids will survive beyond the first 10 million years. The vast majority of star clusters formed during this interaction will disperse, individual stars becoming part of the smooth background of the galaxy. It is thought, however, that a hundred or so most massive clusters will survive to form regular globular clusters, similar to the globular clusters found in our own Milky Way galaxy.
Antenna galaxies take their name from the long antenna-like "arms" that extend far from the nuclei of the two galaxies, better visible by ground-based telescopes. These "tails" were formed during the initial meeting of galaxies, about 200 to 300 million years ago. They give us a glimpse of what can happen when our Milky Way galaxy collides with the neighboring region of Andromeda.
The Daily Galaxy via the University of Texas and NRAO
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