Don't galaxies need dark matter? Growing gap between theory and observation
An international team of researchers led by scientists from the Netherlands reports that they are in the Galaxy AGC 114905 found no traces of dark matter. It is now widely accepted that galaxies can only exist thanks to dark matter, the interaction of which holds them together.
Two years ago, Pavel Mancera Piña and his team from the University of Groningen reported that they had found six galaxies with little or no dark matter. At that time they were told by their colleagues that they had better look, then they would find out that they had to be there. Now, after 40 hours of observation with the Very Large Array (VLA), the scientists confirmed what they had previously established - the existence of galaxies without dark matter.
AGC 114905 is 250 million light years from Earth. It is about a ultra-diffuse dwarf galaxy (UDG)but "dwarf" refers to their brightness, not their size. The galaxy is as big as the Milky Way, but contains about 1000 times fewer stars. Observations and analysis contradict the notion that all Galaxies, and certainly not the dwarf galaxies, can only exist because of the dark matter that holds them together.
Between July and October 2020, the researchers used the VLA to collect data on gas movements in this galaxy for 40 hours. From the observations, they created a graphic that shows the distance of the gas from the galaxy on the X-axis and its speed of rotation on the Y-axis. This is a standard way to check for the presence of dark matter to investigate. In the meantime, the analysis has shown that the movement of the gas in AGC 114905 can be fully explained if one only refers to the visible matter.
The scientists are therefore trying to explain what is happening with the dark matter happened. One of their hypotheses is that AGC 114905 of large neighboring galaxies is dark matter could have got withdrawn. The problem is that there are no such galaxies. To explain this lack of dark matter on the basis of the generally accepted cosmological model Lambda-CDM, we would have to introduce parameters with extreme values far beyond the accepted range. Even on the basis of an alternative model - the modified Newtonian dynamics - we cannot explain the movement of the gas in this galaxy.
The scientists say there is one guess that could alter the conclusions of their research. That assumption is the angle at which they observed AGC 114905. But that angle would have to be very different from our assumptions for the conclusions to point to the existence of dark matter, says Tom Oosterloo, co-author of the study. The research team now has the next UDG. Even if there are no traces of dark matter found, this would be a very strong confirmation of the observations made so far.
It should be remembered at this point that we reported 3 years ago that a team from Yale University discovered the first galaxy without dark matter. The method used by the Dutch is more reliable and more resistant to interference.