There is abundant evidence that galaxies grow by merging with other galaxies.
Telescopes like Hubble have captured many interacting galaxies, including the famous Arp 248.
The Andromeda Galaxy is the closest large galaxy to the Milky Way, and new research suggests that our neighbor has eaten other galaxies in two different periods.
“A few years ago, we found that in the distant regions of Andromeda, there was a signal in the material around the galaxy that the galaxy never grazed, but it grazed very much in two different seasons,” said Geraint Lewis of the recent years. at the University of Sydney.
Lewis is the lead author of a new paper titled “Chemo-dynamical substructure in the M31 inner halo globular clusters: further evidence for a recent event.” The Monthly Notices of the Royal Astronomical Society will publish the paper, and it is available on the pre-press site arxiv.org.
“These new results provide a clearer picture of how our universe has come together – they tell us that in one of the larger galaxies, there has been a gradual feeding of smaller galaxies,” Lewis said in the paper. to release.
Globular groups are the focus of this study.
They are old star clusters with low metallicity. There are at least 150 in the Milky Way, possibly more. They play a role in the evolution of galaxies, but that role is not well understood. Globulars, as they are called, are mostly found in halo galaxies, while their counterparts, open clusters, are found in star clusters.
The researchers behind the work discovered a number of globular bodies in Andromeda’s inner halo that all have the same metallicity. Metallicity refers to the unique composition of stars, with elements heavier than hydrogen and helium called metals in astronomy.
The globulars have lower metallicities than most stars in the same region, suggesting that they came from somewhere else, not Andromeda itself.
It also means that they are older because there was less heavy matter in the early Universe than there is now.
Lewis named the globular group the Dulai Structure, meaning black river in Welsh.
The Dulais Structure is probably a group of between 10 and 20 globular structures unrelated to the orbit of Andromeda. But it is not the only irregular group of globulars.
The Dulais Structure is evidence of Andromeda feeding the globular cluster sometime in the past 5 billion years. Another group is a small group of globulars that are evidence of a second feeding event between 8 and 10 billion years ago.
According to Lewis and his co-authors, globular groups have fewer metals and are much different from other groups in the same region. The Andromeda Galaxy rotates in one direction, and the Dulais Structure rotates in the opposite direction.
For Lewis and his co-authors, the Dulais Structure looks like leftovers from a messy meal. It is a black river with constellations. It’s further evidence that large galaxies merge to form large displays throughout the Universe and that large galaxies cannibalize smaller clusters in a form of galactic cannibalism.
“That leads to the next question, well, what was actually eaten? Because it doesn’t look like one thing, it looks like it’s a collection of things that are slowly being torn apart,” Lewis said.
“We’ve discovered over the last few decades that galaxies grow by cannibalizing — so the smaller galaxies fall in, they get eaten — that’s cannibalism.”
When these feeding events took place, things in the Universe were very tight. Ten billion years ago, there may have been many events in the Universe. This is one of the reasons why astronomers want more powerful telescopes like the James Webb. They can see the light of ancient galaxies and look back farther.
“We know that the Universe was nothing at its birth in the Big Bang, and today it is full of galaxies. Lewis said.
Astronomers would love to know the history of our Milky Way galaxy. We all would. This is hard to do through visuals because we are so ingrained in them.
But Andromeda offers an opportunity to study the evolution of galaxies from the outside, and researchers like Lewis and his colleagues are taking full advantage.
As a spiral galaxy similar to the Milky Way, some of what astronomers are learning about galaxy mergers in Andromeda may apply to our galaxy, too.
But astronomers have a lot of work to do before they can think about the Milky Way. Or about integration and multiple uses. A detailed process of galactic evolution in the universe is the goal.
“What we want to know is, has the Milky Way behaved the same way, or is it different? All of these have interesting implications for the whole picture of how galaxies form,” said Lewis.
“We want, to some degree, to come up with a very accurate clock to tell us when this happened because that’s one thing we need to incorporate into our models of how galaxies evolve.”
As it stands, Lewis and other researchers only have two versions of the Dulais Structure.
Its dimensions are speed and chemistry. Finding the distance of all these objects will provide the third part, which will fill in the history of the globulars and how Andromeda ate them.
Lewis isn’t sure we can call them globulars at this point, and won’t be until there are more. Hence the name “Dulais Structure.”
“This will allow us to sort out the direction, where things are going, and then we can start to run the clock back and see if we can get a coherent picture of when things went down,” he said.
“We can’t call it a galaxy-like object because we don’t know if the signature we’re seeing is from one large interfering object or seven smaller interfering objects. It could be another galaxy.”
Apparently there is something going on with the Dulais Structure and the Andromeda galaxy. But in keeping with his scientific training, Lewis is wary of hard facts at this point.
“It’s opened a new door in terms of our understanding,” Lewis said in a press release. “But exactly what they’re telling us, I think we still have to fix this.”
The authors explain their case clearly in their paper. “Interestingly, the orbital aspect of this Dulais Structure is closely related to the small events recently identified using small globular clusters in the outer region of Andromeda, and this clearly shows a close relationship between the two,” the authors they summarize in their papers.
“If this connection is confirmed, the natural explanation of the globular groups in the Dulais Structure is that they follow the multiplication of the great parent (about 10).11 solar system) in Andromeda’s halo in the past few billion years, which may have occurred as part of a larger cluster.
This article was originally published by Universe Today. Read the first article.
