GERMANY: According to the standard cosmological model, most galaxies are encircled by a halo of dark matter particles. Although this dark matter halo is invisible, the nearby galaxies are strongly gravitationally pulled in by it due to its mass.
This universe view is contested by a recent study from the Universities of Bonn (Germany) and Saint Andrews (Scotland). The findings imply that the dwarf galaxies in the Fornax Cluster, the second closest galaxy cluster to Earth, are devoid of such dark matter halos.
Particularly, scientists have developed a novel method of verifying the standard model based on the degree to which gravitational tides from nearby larger galaxies perturb dwarf galaxies.
According to the principal author of the article, Elena Asencio, a PhD candidate at the University of Bonn, “Tides happen when gravity from one body pulls unevenly on various sections of another body. These are comparable to Earth’s tides, which form when the moon pulls more forcefully on the side of the planet that faces the moon.”
According to Pavel Kroupa, the Fornax Cluster features a significant population of dwarf galaxies, professor at the Universities of Bonn and Prague’s Charles University. Some of these dwarfs appear warped in recent observations, as though the cluster environment has disturbed them, it has been discovered.
The Standard Model does not predict such fluctuations in the Fornax dwarfs. This is because the dark matter halos of these dwarfs should in part protect them from the tides caused by the cluster, according to the standard model.
The authors determined the expected level of disruption of the dwarfs based on internal properties and separation from the gravitationally powerful cluster centre. Large galaxies with little stellar mass and galaxies near the cluster centre are more vulnerable to annihilation. They compared the results to the degree of the disturbance they had seen in pictures taken by the VLT Survey Telescope of the European Southern Observatory.
Scientists concluded that the standard model could not account for the observed morphologies of the Fornax dwarfs in a self-consistent manner.
They carried out the investigation once more using Milgrom dynamics (MOND). The MOND theory suggests a correction to Newtonian dynamics via which gravity experiences an increase in the regime of low accelerations, rather than assuming dark matter halos surrounding galaxies.
We weren’t sure the dwarf galaxies in MOND would be able to endure the harsh environment of a galaxy cluster due to the lack of protective dark matter halos in this model, according to Dr Indranil Banik from the University of St. Andrews. However, our findings demonstrate a striking concordance between the Fornax dwarfs’ amount of disruption as predicted by MOND and observations.
“It is wonderful to see that the data we gathered with the VLT survey telescope allowed such a thorough evaluation of cosmological models,” stated Aku Venhola from the University of Oulu in Finland and Steffen Mieske from the European Southern Observatory.
The University of St. Andrews’ Dr Hongsheng Zhao further stated, “Our findings have significant ramifications for fundamental physics. We anticipate additional clusters will have more perturbed dwarfs; other teams should confirm this.”
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