Space and Physics
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![An area of deep space with thousands of galaxies in various shapes and sizes on a black background. Most are circles or ovals, with a few spirals. More distant galaxies are redder in colour and smaller, down to being mere dots, while closer galaxies are a bit larger and white or blueish. A few gold-coloured galaxies are bunched closely together in the centre. Bright stars surrounded by spikes lie in our galaxy.]](https://assets.iflscience.com/assets/articleNo/83412/aImg/90383/hubble-jwat-deep-field-s.png)
Rotation seems to be one of those quintessential characteristics of galaxies. Whenever we see spiral galaxies, we can easily image them spinning. But not all galaxies rotate; repeated collisions and interactions with other galaxies can strip these cosmic objects of their angular momentum. This process is believed to take many billions of years, so imagine the face of scientists finding a non-rotating galaxy less than 2 billion years after the Big Bang.
The rest of this article is behind a paywall. Please sign in or subscribe to access the full content.XMM-VID1-2075 was already known for being one of the most massive known galaxies in the early universe. This galaxy and several others were observed by W.M. Keck Observatory in Hawaiʻi as part of the MAGAZ3NE (Massive Ancient Galaxies at z>3 NEar-Infrared) survey. This object and two others of similar age were followed up with JWST to work out their motion.
“This one in particular did not show any evidence of rotation, which was surprising and very interesting,” lead author Ben Forrest, from the University of California, Davis, said in a statement.
“Previous MAGAZ3NE observations had confirmed this was one of the most massive galaxies in the early universe, with already several times as many stars as our Milky Way, and also confirmed that it was no longer forming new stars, making it a compelling target for follow-up observations.”
The three objects, while similar, present very different internal dynamics. One is clearly rotating, one looks a bit messy, and XMM-VID1-2075 of course shows no rotation, but very chaotic internal motions from its stars. Its size, lack of recent star formation, and lack of rotation might all come from the same mechanism. Instead of several small collisions that slowed the galaxy, the team suggests a single merger with a galaxy that was rotating pretty much in the opposite direction.
There is supporting evidence for this idea. “For this particular galaxy, we see a large excess of light off to the side. And so that's suggestive of some other object which has come in and is interacting with the system and potentially changing its dynamics,” Forrest said.
The finding is certainly surprising, and it is unlikely that this object is unique. By finding out how many such galaxies are out there, astronomers can test models of galaxy formation.
“There are some simulations that predict that there will be a very small number of these non-rotating galaxies very early in the universe, but they expect them to be quite rare. And so this is one way in which we can test these simulations and really figure out how common they are, and that can then give us information about whether our theories of this evolution are correct,” Forrest said.
The study is published in the journal Nature Astronomy.
