No dark matter halos

dwarf galaxy

Image: dwarf galaxy NGC1427A flies through the Fornax Cluster of galaxies and undergoes turbulence that would not have been possible if this galaxy were surrounded by a heavy, stretching dark matter halo, as required by standard cosmology.
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Credit: ESO

Dwarf galaxies are small, faint galaxies that can usually be found in galaxy clusters or near larger galaxies. For this reason, they may be affected by the gravitational effects of their larger companions. “We present an innovative way to test the Standard Model based on how much dwarf galaxies are perturbed by gravity and tides from larger neighboring galaxies,” said Elena Asensio, a doctoral student at the University of Bonn and lead author of the story. Tides arise when the gravity of one object differently pulls different parts of another object. These are similar to Earth’s tides, which arise because the Moon is pulling more strongly on the side of the Earth that faces the Moon.

The Fornax Cluster contains a large number of dwarf galaxies. Recent observations show that some of these dwarfs appear deformed, as if disturbed by the cluster environment. “Such disturbances in Fornax dwarfs are unexpected according to the standard model,” said Pavel Krupa, a professor at the University of Bonn and Charles University in Prague. This is because, according to the Standard Model, the dark matter halos of these dwarfs must partially protect them from the tides stirred up by the mass.”

The authors analyzed the expected level of turbulence of the dwarfs, which depends on their internal characteristics and their distance from the gravitationally strong cluster center. Galaxies of large but low-mass stellar masses and galaxies close to the center of the cluster are easy to disturb or destroy. They compared the results to the level of perceived turbulence evident from images taken with the European Southern Observatory’s VLT Survey Telescope.

“The comparison showed that if one wanted to explain observations in the Standard Model,” said Elena Ascencio, “Fornax dwarfs must indeed be destroyed by gravity from the center of mass even when the tides they raise on a dwarf are sixty-four times weaker than the dwarf’s self-gravity.” Not only is it self-evident, but it also goes against previous studies, which found that the external force needed to disturb a dwarf galaxy is roughly the same as the dwarf’s self-gravity.

Contradiction with the Standard Model

From this, the authors conclude that, in the Standard Model, the observed morphology of Fornax dwarfs cannot be explained in a self-consistent manner. They repeated the analysis using Milgromian dynamics (MOND). Rather than assuming dark matter halos surrounding galaxies, MOND theory proposes a correction for Newtonian dynamics in which gravity experiences a boost in the low acceleration regime.

“We were not sure that dwarf galaxies would be able to survive in the harsh environment of a galactic crowd at MOND, due to the absence of protective dark matter halos in this model – admitted Dr. Indranel Panik from the University of St Andrews -” but our results show a remarkable agreement between the observations and MOND forecasts for the Fornax dwarf disorder level.

Aku Venhola of the University of Oulu (Finland) and Stephen Miski of the European Southern Observatory, who are co-authors of the study, said.

This is not the first time that a study examining 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. said Pavel Krupa, a member of the “Modeling” of Interdisciplinary Research Areas and “Material” at the University of Bonn.

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

Participating Institutions and Funding:

In addition to the University of Bonn, the study included the University of St 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 Technology Facilities Council and the German Academic Exchange Service.

the post: Elena Asencio, Indranil Banik, Steffen Mieske, Aku Venhola, Pavel Kroupa, Hongsheng Zhao: Distribution and morphology of the Fornax Cluster dwarf galaxies suggest that they lack dark matter. Monthly Notices of the Royal Astronomical Society; https://doi.org/10.1093/mnras/stac1765 / https://arxiv.org/abs/2208.02265


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