Galaxies DF2 and DF4 are unusual star clusters. They appear to be devoid of dark matter, which is contrary to our understanding of galaxies’ creation mechanisms. The researchers who found them now believe they have figured out how they developed. They resulted from a complex cosmic collision between two galaxies. According to the model, two dwarf galaxies circling their bigger partner NGC 1052 collided at a speed of around 300 kilometers per second 8 billion years ago, as published in the journal Nature. The high-velocity collision caused the two galaxies to travel through one another, separating the dark matter from the gas.
This left a path of ultra-diffuse galaxies the size of the Milky Way, but with far fewer stars and far less dark matter than their parents. The researchers believe that some of the original dwarf galaxies, which are now richer in dark matter, are still out there, with dark-matter-free ones scattered among them.
These post-merger trail galaxies would include DF2 and DF4. The simulation is amazing, and it explains why these two remarkable clusters of stars contain around 100 times less dark matter than the theory of galaxy formation would suggest. This is why the finding of these galaxies was met with skepticism as well as excitement. This creation scenario may assist explain their genesis, but their existence ultimately raises a critical astrophysics question concerning the nature of dark matter.
We just do not understand it. Dark matter is the greatest explanation we have for explaining decades of observations, but it’s also rather poor, as many astrophysicists will tell you. The reason for this is that no one has yet been able to determine what dark matter is. According to what we know about it, it only interacts gravitationally with ordinary stuff. That’s why a high-speed collision might split it from galaxies. Alternatives to dark matter include Adjusted Newtonian Dynamics (MOND), which proposes that some physical principles are incorrect and must be modified to explain what we see in the cosmos.
The presence of dark-matter-free galaxies casts doubt on ideas like MOND, implying that dark matter is a material that galaxies may or may not possess. When it comes to our cosmological ideas and the role dark matter plays in them, understanding phenomena like DF2 and DF4 is crucial. Dark matter must be lost or acquired in mergers, and its presence or absence impacts the history of these galaxies.
