Signs of Disturbance in Nearby Dwarf Galaxies Point to an Alternative Theory of Gravity

Dwarf galaxies are small faint galaxies that are usually found in clusters of galaxies or near larger galaxies. Because of this, they might be affected by the gravitational effects of their larger companions. “We introduce an innovative way to test the conventional model based on the amount of dwarf galaxies perturbed by the gravitational tides of nearby larger galaxies,” said Elena Asencio, PhD student at the University of Bonn and lead author of the story. . Tides occur when one body’s gravity pulls differently on different get-togethers of another body. These are similar to tides on Earth, which occur because the moon pulls more strongly on the side of the Earth that faces the moon.

The Fornax cluster has a rich population of dwarf galaxies. Recent observations show that some of these dwarfs appear distorted, as if they had been disturbed by the environment of the cluster. “Such perturbations in Fornax dwarfs are not expected according to the Standard Model,” said Pavel Kroupa, a professor at the University of Bonn and Charles University in Prague. “Indeed, according to the standard model, the dark matter halos of these dwarfs should partly protect them from the tides raised by the cluster.”

The authors analyzed the level expected disturbance of the dwarfs, which depends on their internal properties and their distance from the center of the gravitationally powerful cluster. Large but low stellar mass galaxies and galaxies close to the center of the cluster are more easily disrupted or destroyed.

“The comparison showed that, if one wants to explain the observations in the common model” – said Elena Asencio – “the dwarfs of Fornax should already be destroyed by gravity from the center of the cluster even when the tides it raises on a dwarf are sixty -four times weaker than the dwarf’s own gravity.” Not only is this counterintuitive, she says, but it also contradicts previous studies, which found that the external force needed to disrupt a dwarf galaxy is about the same as the dwarf’s self-gravity.

Contradiction with the regular model

From this, the authors concluded that, in the conventional model, there is no It is not possible to explain the observed morphologies of Fornax dwarfs in a car-coherent way. They repeated the analysis using Milgromian dynamics (MOND). Instead of assuming halos of dark matter surrounding galaxies, the MOND theory suggests a correction to Newtonian dynamics whereby gravity experiences an increase in the low acceleration regime.

“ We weren’t sure that dwarf galaxies would be able to survive the extreme environment of a galaxy cluster in the WORLD, due to the lack of protective halos of dark matter in this model – admitted Dr Indranil Banik of the University of St Andrews – “but our results show remarkable agreement between observations and MOND expectations for the level of disturbance of Fornax dwarfs.”

“There It is exciting to see that the data we have obtained with the VLT telescope has allowed such thorough testing of cosmological models,” said Aku Venhola from the University of Oulu (Finland) and Steffen Mieske from the European Southern Observatory, co-authors of the study.

This is not the first time that a study testing the effect of dark matter on the dynamics and evolution of galaxies has concluded that observations are best explained when they are not surrounded by dark matter. “The number of publications showing incompatibilities between observations and the dark matter paradigm continues to increase every year. It’s time to start investing more resources in more promising theories,” said Pavel Kroupa, a member of the transdisciplinary research areas “Modelling” and “Matter”. ” at the University of Bonn.

Dr Hongsheng Zhao of the University of St Andrews added: “Our results have major implications for fundamental physics. We expect to find more perturbed dwarfs in other clusters, a prediction that other teams should verify.”

Participating Institutions and Funding:

In addition to the University of Bonn, the study involved the University of Saint Andrews (Scotland), the European Southern Observatory (ESO), the University of Oulu (Finland) and Charles University in Prague (Czech Republic). The study was supported by the University of Bonn, the UK Science and Technological innovation Services Council and the German Academic Trade Company.

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