Gas is the raw material that stars are made of Galaxies regenerate. But galaxies also emit huge clouds of gas — material ejected by supernovae, among other things. Astronomen haben jetzt erstmals nachgewiesen, dass dieses “Abgas” tatsächlich deutlich “schmutziger” ist als der Einstrom: Während Letzterer primär aus Wasserstoff und Helium besteht, wiesen die Forscher im Ausstrom einer 500 Millionen Lichtjahre entfernten Galaxie zahlreiche schwere Elemente darunter Sauerstoff, Eisen und Kohlenstoff distance.

Galaxies are the stellar factories of the universe, where countless new stars grow in star-forming regions. But to do that, star carriers constantly need fresh supplies of hydrogen and helium – the elements that stars are primarily made of. Only through nuclear fusion inside it, then are the heavier elements formed. For galaxies, this means that their star formation can only continue if they have new gas in them or can attract them. “To do this, huge clouds of gas are sucked into galaxies,” explains co-author Deanne Fisher of Swinburne University in Australia.

“Frisbee” with gas withdrawal

However, this flow of gas into the galaxy – also known as accretion – is not a one-way street: a galaxy that is actively forming stars is also emitting gas. The balance of accretion and outflow is an important factor affecting the growth, mass, and size of a galaxy. But until now, astronomers could only guess if and how the composition of the gases flowing in and out of the galaxy differed. Most galaxies are so unfavorably located in our field of view that gas flows can only be partially distinguished and can be examined by spectroscopic analyses.

The research team has now given the research team the first opportunity to examine the galaxy’s “exhaust plume” more closely. Unlike most other galaxies, Mrk 1486 turns its narrow side toward us. This enabled astronomers to clearly see the inflows and outflows. “Think of the galaxy as a Frisbee,” explains co-lead author Alex Cameron of the University of Oxford. The flowing gas enters the galaxy on the side of the disk and condenses to form new stars. When these stars explode again, they release new gases from the galaxy above and below.

The leaking gas is rich in heavy metals

Astronomers were able to observe these gases, which appear perpendicular to the main plane of the galaxy, for the first time specifically in MRk 1486 and determine their elemental composition with the help of an instrument on the telescopes of the Keck Observatory in Hawaii. “Using what is known as a Keck Cosmic Web Imager, we were able to confirm that the incoming gas consisted of hydrogen and helium,” Fisher says. “We were also able to observe that stars emerging from this fresh gas later eject massive amounts of material out of the system again – primarily through supernovae.” In MRk 1486, this ejected material is clearly visible up and down and is a mixture of many heavy elements, including oxygen, carbon and iron. The team was able to detect the spectral signatures of half of the periodic table in this gas.

This is the first time that astronomers have succeeded in examining a galaxy’s exhaust gas flow in more detail. “This is important for astronomy because it also allows us to limit the forces and influencing factors that affect how galaxies produce their stars,” Fisher explains. “It brings us one step closer to understanding how and why galaxies look the way they do — and how long they last.”

Coyle: Dean Fisher (Swinburne University, Australia) et al., The Astrophysical Journal, doi: 10.3847/2041-8213/ac18ca

© wissenschaft.de – Nadia Podebrigar