Dark Matter Core Defies Explanation

I gave an explanation of Dark Matter in an earlier post for this article that I have recently read and find interesting. Astronomers were able to observe a clump of dark matter left behind after a collision of galaxy clusters. It was theorized that dark matter in galaxy clusters would stay anchored with the galaxies even after violent collisions, however this new development has destroyed that theory when with what they call a Dark Matter Core was left behind with an abundance of hot gas after two of these galaxy clusters collided, and continued on as a merged galaxy cluster called Abel 520. It was initially observed in 2007 and was shrugged off as unreal due to poor data, however as new data has come in, the data was confirmed that there was a dark matter core left behind. This has forced researchers to question and redefine how they believe dark matter to work.

The image above (pictured the core of the merging galaxy cluster Abel 520 and it's distribution of hot gas, galaxies, and dark matter) and article can be found here