By producing stars, galaxies “pollute” the cosmos

The process of the influx of atoms into galaxies – known as growth – and their eventual expulsion – known as “outflows” – is an important mechanism that controls the growth, mass, and size of galaxies. But the exact composition of these incoming and outgoing drug streams had never been determined until now. Researchers fromARC Center of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), investigated the case.

Better understand primitive chemistry

Star formation is a research topic that fascinates many scientists. And with good reason, this complex phenomenon can help to better understand the history of our solar system and, above all, it can bring new clues about the primitive chemistry that made life possible to appear on our planet.

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When a galaxy produces stars, it attracts huge clouds of gas and dust; these are fragmented into several protostellar nuclei, which become stars by contracting on themselves. The remaining material forms a growth disk in the periphery in which planets can be formed.

A team of astronomers, led by Alex Cameron and Deanne Fisher, were particularly interested in the galaxy Mrk 1486. ​​The latter is located about 500 light-years from the Sun and is currently undergoing a period of very rapid star production. . It is also ideally located for observations. Using a new imaging system located at the WM Keck Observatory in Hawaii, Keck Cosmic Web Imagerscientists set out to study the chemical elements present in the incoming and outgoing streams of this galaxy.

A much more metallic material flow at the outlet

While the first gas clouds consist of hydrogen and helium, scientists have found that stars made from this gas eventually propel a huge amount of matter out of the system, mostly through supernovae. But this material contains many chemical elements, including oxygen, carbon and iron, explains Deanne Fisher, co-author of the study.

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We have discovered that there is a very clear structure for how gases get in and out “, Explained Dr. Alex Cameron on the astro3D page. The team calculated that the metallicity of the outflow of material from Mrk 1486 is 1.6 times greater than the average metallicity of the interstellar medium and more than 6.3 times greater than the low metal incoming gas.

To better understand the phenomenon, the specialist suggests the following image: you should see the galaxy as a spinning frisbee. Gas from the cosmos, relatively “unpolluted”, enters the galaxy from the outside (at the perimeter of the frisbee), then condenses to form new stars.

But much later, when these stars collapse or explode, they emit other gases that contain new elements, both from the top and bottom of the galaxy where they are located. These elements are forged in the heart of stars by nuclear fusion. When a star dies, they disperse into the universe and form the “raw material” that will feed other stars and planets.

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This work is important to astronomers because, for the first time, we were able to set limits on the forces that greatly affect how galaxies make stars. says Deanne Fisher. This study, which highlights the difference in metallicity of the substance streams, has thus made it possible to better understand how and why galaxies are what they are today.

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