What goes into a “cleaner” galaxy than what comes out?

https://www.youtube.com/watch?v=MEtu6vJFGdg

What flows in a galaxy

On August 30, 2021, astronomers described a process by which clouds of pure hydrogen and gaseous helium are drawn into galaxies, to be used in the making of new stars. Stars convert these very simple elements – hydrogen and helium – into more complex elements, including oxygen, carbon, and iron. And then the galaxies pump that “exhaust,” as astronomers called it, back into intergalactic space. Supernova explosions are the source of most of the outflow. The video above illustrates this process, showing the concept of an artist from the galaxy Mrk 1486, who is going through a period of very rapid star formation. It shows matter released by stars via supernovae, loaded with elements like oxygen and iron, seeping out of the galaxy. In other words, these astronomers said:

… What goes into a galaxy is much cleaner than what comes out of it.

Astronomers Alex Cameron and Deanne Fisher of ASTRO 3D in Australia – a consortium of nine Australian universities and international partners – led this research. The team used new equipment called the Keck Cosmic Web Imager at the WM Keck Observatory in Hawaii. Peer review Letters from astrophysical journals published the new book on August 30.

So it’s pretty much the same story we’ve known for decades. These are elements forged inside stars, then released via supernovae. We are stars, right? But this story focuses on the process as it occurs on a galaxy scale.

Astronomers describe the process of flooding atoms in galaxies as accumulation. They use the word exit for the eventual expulsion of atoms from galaxies. Until now, said these astronomers, they could only guess at the composition of this flow of matter in and out. Yet accretion and flow are vital processes within galaxies. They govern the growth, mass and size of galaxies. And so astronomers want to understand them. In this new research, for the first time, astronomers were able to confirm the complete cycle in a galaxy other than our home galaxy, the Milky Way.

Mrk 1486: Perfect for study

Researchers studied the star-forming galaxy called Mrk 1486. ​​Alex Cameron said:

We have found that there is a very clear structure to how gases come in and go out. Imagine the galaxy is a spinning Frisbee. The gas enters relatively unpolluted from the outer cosmos, around the perimeter, and then condenses to form new stars. When these stars later explode, they expel other gases – now containing these other elements – up and down.

Mrk 1486 was the ideal candidate for observation, these astronomers said, because it sits right next to Earth. And that means that astronomers could see the gas coming out more easily than if, for example, they were looking at a galaxy from the front. Deanne Fisher added:

This work is important for astronomers because for the first time, we were able to put limits on the forces that strongly influence the way galaxies make stars. It brings us one step closer to understanding how and why galaxies look like they are, and how long they will last.

Conclusion: for the first time, astronomers were able to measure the influx of hydrogen and helium atoms, and the exit of more complex atoms, in a galaxy other than our Milky Way.

Bottom line: Pure hydrogen and gaseous helium flow in a galaxy. It is used to make new stars. These stars create new elements, which are then released into intergalactic space.

Source: DUVET survey: direct mapping of the Te-based metallicity of outgoing flows enriched in metals and incoming flows poor in metals at Mrk 1486

Via science in public