A growing body of evidence supports the idea that galaxies grow larger by merging with each other.
Telescopes like the Hubble have captured many interacting galaxies.
A new study shows that our neighbor has eaten other galaxies in two separate eras.
The Chemo-dynamical substructure in the M31 inner halo clusters is further evidence for a recent accretion event. The paper will be published in the monthly Notices of the Royal Astronomical Society.
Lewis said in a press release that the new result provides a clearer picture of how the local universe came together.
The center of this research is the clustering of globulins.
Older associations of stars have lower metallicity. At least 150 are in the sky. They are involved in the evolution of the universe. While open clusters are found in the disks, globulars are found in the halo.
There is a group of globulars in the inner halo that all have the same metallicity. Stars with elements heavier than hydrogen and helium are referred to as metallicity.
The lower metallicity of the globulars means they came from somewhere else.
Since there were less heavy elements in the early Universe, they are older.
The Dulai Structure is named after the black stream in Welsh.
There is a group of between 10 and 20 globulars in the Dulais structure. They're not the only ones.
The Dulais structure shows that Andromeda fed on a group of globulars. There is evidence of a second feeding event between 8 to 10 billion years ago.
Lewis and his co-authors say that the globular clusters are different from other clusters in the same region. The Dulais structure moves in different ways.
The Dulais structure looks like leftovers from a meal. There are bright star clusters in the stream. It's further evidence that massive galaxies merging to create giant displays throughout the Universe and that larger galaxies consuming smaller stars in a type of cannibalism.
What was actually eaten is the next question. Lewis said that it looks like it has been a collection of things that are torn apart.
Over the last few decades, we've come to realize that galaxies grow by eating small systems and that it's called galactic cannibalism.
The Universe was more tightly focused when these feeding events happened. There may have been more of these events in the past. Astronomers want more and more powerful telescopes. They can see the light from the past.
The universe was featureless when it was born, and today it's full of stars. Did they grow or were they fully formed? Lewis made a statement.
Astronomers want to know the history of our own galaxy. All of us would. We're embedded in it so it's hard to do that.
Lewis and his colleagues are taking full advantage of the chance to study the evolution of the galaxy from an outside perspective.
As a spiral galaxy like the Milky Way, some of the information about galaxy mergers can apply to ours.
Astronomers have more work to do before they can make a conclusion about the universe. It's about mergers and consumptions as a whole. The goal is to have a more detailed look at the evolution of the universe.
We want to know if the Milky Way is the same as the other one. Lewis said that the consequences of both of those are interesting.
One thing we need to include in our models of how galaxies evolve is a clock that tells us when these events happened.
Lewis and the other researchers only have a two-dimensional view of the structure.
Speed and chemistry are measured. The history of the globulars will be filled out by finding the distances of all these objects.
Lewis isn't sure we can call them globulars at the moment, and he won't be until there is more data. "Dulais structure" is what it's called.
"That will allow us to work out where things are going, and then we can run the clock backwards and see if we can get a clear picture of when things fell in," he said.
We don't know if the signature we see is from one big object disrupting or seven smaller objects disrupting, so we can't call it a galaxy. That's the reason we refer to it as a structure.
Something is going on with the Dulais structure. Lewis is cautious about conclusions at this point in time.
Lewis said in a press release that it has opened a new door. I think we need to work that one out.
In their paper, the authors state their case. The authors say that the orbital axis of the Dulais Structure is close to that of the younger accretion event recently identified using a sub-population of globular clusters.
The accretion of a progenitor (about 10 11 solar mass) into the halo of Andromeda may be the reason for the kinematics of the Dulais Structure.
This article was published in the past. The original article is worth a read.
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