Evidence is growing that galaxies increase in size when they merge with other galaxies.
Telescopes such as the Hubble have captured many interacting galaxies including some well-known ones. Arp 248.
The Andromeda Galaxy is the closest large galaxy to our Milky Way. A new study has shown that our neighbor may have consumed other galaxies in different epochs.
“A few decades ago, we discovered in the far outskirts Of Andromeda that there was an indication in the objects orbiting it that it hadn’t been grazing. However, it had eaten large quantities of material in two distinct times.” Geraint Lewis, University of Sydney
Lewis is the author of a paper entitled “A New Paper”The M31 inner haloglobular clusters show a chemo-dynamical structure: Additional evidence of a recent accretion.“The Monthly Notices of The Royal Astronomical SocietyThe paper will be published and is currently available at Arxiv.org is a pre-press site.
“What this new result does is provide a clearer picture of how our local universe has come together – it is telling us that at least in one of the large galaxies, there has been this sporadic feeding of small galaxies,” Lewis In a press release.
Globular clustersThese are the central focus of this research.
These are older star associations with lower metallicity. There are probably more than 150 of them in the Milky Way. While they are important in galactic development, the exact role of these objects is not known. Globulars are known to be more common in a galaxy’s “halo”, while their counterparts, open-clusters, can be found in the galactic disks.
Researchers behind this research identified a population globulars within Andromeda’s inner halo with the same metallicity. Metallicity refers the elemental makeup stars with elements heavier that hydrogen and helium, also known as metals in Astronomy.
The metallicity of the globulars is lower than that of other stars in the same area, which means they are not Andromeda-derived.
This also means that they are older, as there were less heavy elements in the early Universe.
Lewis gave the collection of the globulars the Dulai structure, which translates to black stream in Welsh.
The Dulais Structure may be a group between 10 and 20 globulars that is not in alignment with Andromeda’s orbit. They’re not the only group of globulars misaligned.
The Dulais structure is evidence that Andromeda ate on a group or globulars during the last 5 billion year. Another group includes a sub-population globulars, which is evidence of another feeding event that occurred between 8 and 10 billion years ago.
Lewis and co-authors believe that globular clusters possess lower metallicity, and are kinematically separate from other clusters in this region. The Andromeda Galaxy rotates in one direction, while the Dulais Structure is able to move in a different way.
Lewis and his co-authors think the Dulais Structure is leftovers from messy meals. It is a dark stream with vibrant star clusters. This is further evidence of the fact that large galaxies combine to create massive displays across the Universe. It also shows that smaller globulars are consumed by larger galaxies in a form of galactic cannibalism.
This leads us to the next question: what was actually eaten? It doesn’t seem like there was one thing that was consumed. It looks like there were many things that were slowly being torn down.” Lewis.
“We’ve come to realize over the last few decades that galaxies grow by eating smaller systems – so little galaxies fall in, they get eaten – it’s galactic cannibalism.”
These feeding events caused matter to be more concentrated in the Universe. Ten billion years ago, the Universe may have had more of these events. This is why astronomers want more powerful telescopes such as the James Webb. They can see past galaxies’ light and also look further back in the past.
“We know that the Universe had no features at its birth in the Big BangIt’s today full of galaxies. Did those galaxies grow or were they born as a complete formation? Lewis .
Astronomers want to know the history and origins of our Milky Way Galaxy. We all wish we could. Because we are embedded in it, it’s hard to make this through observations.
However, Andromeda offers an opportunity to study galaxy development from an outside perspective. Lewis and his collaborators are making the most of it.
Because our galaxy is a spiral galaxy like the Milky Way and can be merged with other galaxies, some of the information astronomers learned about Andromeda’s galaxy mergers can also apply to it.
Astronomers still have a lot of work to do before they can draw any conclusions about the Milky Way. Or general information about mergers or consumptions. The goal is to provide a more complete timeline of galactic evolution throughout all of the Universe.
“What do we want to find out is, is the Milky Way doing the same thing or is it something else? Both have interesting implications for how galaxies are formed,” Lewis explains. .
“We need to come up with a better clock to tell us when these events took place. That’s one thing that we must include in our models for how galaxies change.”
Lewis and other researchers have only a two-dimensional historical view, as it stands.
These dimensions are speed, chemistry, and gravity. A third dimension will be created by determining the distances of all the objects. This will help to complete the history of the globeulars and the way that Andromeda ate them.
Lewis isn’t sure if we can label them globulars yet, and won’t be until there’s more information. Thus the name “Dulais Structure”.
He said, “That will allow us to calculate orbits, where they are going, then we can run the clock backwards to see if it is possible to get a coherent picture of when everything fell in.” .
“We could not name it an object like a galaxie because we don’t know if the signatures we see are from one large object disrupting or seven smaller objects disrupting. It is a structure, not a galaxy.
Evidently, there is something happening with the Dulais Structure as well as the Andromeda Galaxy. Lewis, a scientist by training, is cautious about drawing firm conclusions at this stage.
Lewis stated, “It has opened a new door for our understanding.” In a press release. “But it’s telling me exactly what it is, I believe we still need to work that one.”
In their paper, the authors clearly state their case. “Interestingly, this Dulais Structure orbital axis is closely aligned and that of the younger event of accretion, recently identified using a subpopulation of globular clumps in the outer-halo of Andromeda. This strongly suggests a causal relation between the two,” stated the authors. Their paper summarizes.
“If this connection is confirmed then a natural explanation of the kinematics found in the Dulais Structure’s globular Clusters is that they trace the accretion a substantial progenitor (about 10)11solar masses) into the Halo of Andromeda over the last billion years. This may have happened as part of larger group infall.”
This article was first published by Universe Today. Please read the Original article.
