Dwarf galaxies found without dark matter halos – Transcontinental Times

GERMANY: According to the standard cosmological model, most galaxies are surrounded by a halo of dark matter particles. Although this dark matter halo is invisible, its mass strongly gravitates towards nearby galaxies.

This world view is disputed by a recent study by the Universities of Bonn (Germany) and Saint Andrews (Scotland). The results imply that the dwarf galaxies in the Fornax cluster, the second closest cluster of galaxies to Earth, are free of such dark matter halos.

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In particular, scientists have developed a novel method to verify the Standard Model based on the extent to which gravitational tides from nearby larger galaxies disrupt dwarf galaxies.

According to the article’s lead author, Elena Asencio, a PhD student at the University of Bonn, “Tides are formed when the gravity of one body acts unevenly on different parts of another body. These are comparable to the tides on Earth that occur when the moon pulls harder on the lunar side of the planet.”

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According to Pavel Kroupa, professor at the Universities of Bonn and Prague’s Charles University, the Fornax Cluster has a significant population of dwarf galaxies. Some of these dwarfs appear to be skewed in recent observations, as if discovered to have been disturbed by the cluster environment.

The standard model does not predict such fluctuations in the fornax dwarfs. According to the standard model, the dark matter halos of these dwarfs are supposed to partially protect them from the tides caused by the cluster.

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The authors determined the expected magnitude of the dwarfs’ disturbance based on internal properties and separation from the high-gravity cluster center. Large, low stellar mass galaxies and galaxies near the center of the cluster are more prone to annihilation. They compared the results to the extent of the disturbance they had seen in images from the European Southern Observatory’s VLT Survey Telescope.

The scientists concluded that the Standard Model could not explain the observed morphologies of the fornax dwarfs in a self-consistent way.

They ran the investigation again using Milgrom Dynamics (MOND). The MOND theory proposes a Newtonian dynamics correction whereby gravity experiences an increase in the region of low accelerations, rather than assuming dark matter halos surrounding galaxies.

according to dr Indranil Banik of the University of St Andrews, we were unsure whether the dwarf galaxies in MOND would be able to withstand the harsh environment of a galaxy cluster, as there are no protective dark matter halos in this model. However, our results show remarkable agreement between the MOND-predicted extent of disruption by the fornax dwarfs and observations.

“It is wonderful to see that the data we collected with the VLT survey telescope enabled such a thorough assessment of cosmological models,” explained Aku Venhola from the University of Oulu in Finland and Steffen Mieske from the European Southern Observatory.

dr Hongsheng Zhao from the University of St. Andrews further explained: “Our results have significant implications for basic physics. We anticipate that additional clusters will have more disturbed dwarfs; other teams should confirm this.”

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