No traces of dark matter halos

In accordance with the usual mannequin of cosmology, the overwhelming majority of galaxies are surrounded by a halo of darkish matter particles. This halo is invisible, however its mass exerts a robust gravitational pull on close by galaxies. A brand new research performed by the College of Bonn (Germany) and the College of Saint Andrews (Scotland) challenges this view of the Universe. The outcomes recommend that dwarf galaxies within the second-closest cluster of galaxies to Earth, often known as the Fornax cluster, are freed from such darkish matter halos. The research appeared within the journal Royal Astronomical Society Month-to-month Notices.

Dwarf galaxies are small, faint galaxies which might be normally present in galaxy clusters or close to bigger galaxies. For that reason, they could possibly be affected by the gravitational results of their bigger companions. “We’re introducing an revolutionary approach to take a look at the Normal Mannequin primarily based on the quantity of dwarf galaxies perturbed by gravitational tides from close by bigger galaxies,” mentioned Ph.D. Elena Asencio. scholar on the College of Bonn and fundamental writer of the story. Tides happen when one physique’s gravity pulls otherwise on totally different elements of one other physique. These are just like tides on Earth, which happen as a result of the moon pulls extra strongly on the aspect of the Earth that faces the moon.

The Fornax cluster has a wealthy inhabitants of dwarf galaxies. Current observations present that a few of these dwarfs seem distorted, as if they’d been disturbed by the surroundings of the cluster. “Such perturbations in Fornax dwarfs should not anticipated in accordance with the Normal Mannequin,” mentioned Pavel Kroupa, a professor on the College of Bonn and Charles College in Prague. “Certainly, in accordance with the usual mannequin, the darkish matter halos of those dwarfs ought to partly defend them from the tides raised by the cluster.”

The authors analyzed the anticipated degree of disturbance of the dwarfs, which will depend on their inner properties and their distance from the middle of the gravitationally highly effective cluster. Giant however low stellar mass galaxies and galaxies near the middle of the cluster are extra simply disrupted or destroyed. They in contrast the outcomes with their noticed degree of disturbance evident from pictures taken by the European Southern Observatory’s VLT Survey Telescope.

Elena Asencio clarifies that “the comparability confirmed that, if one desires to clarify the observations in the usual mannequin. The dwarfs of Fornax ought to already be destroyed by gravity from the middle of the cluster even when the tides that it raises on a dwarf are sixty-four occasions weaker”. than the dwarf’s personal gravity.” Not solely is that this counterintuitive, she says, however it additionally contradicts earlier research, which discovered that the exterior drive wanted to disrupt a dwarf galaxy is roughly the identical because the dwarf autogravity.

Contradiction with the usual mannequin

From this, the authors concluded that, in the usual mannequin, it isn’t doable to clarify the noticed morphologies of Fornax dwarfs in a self-consistent manner. They repeated the evaluation utilizing Milgromian dynamics (MOND). As an alternative of assuming halos of darkish matter surrounding galaxies, the MOND concept proposes a correction to Newtonian dynamics whereby gravity experiences a rise within the low acceleration regime.

“We weren’t positive that dwarf galaxies would be capable of survive the acute surroundings of a galaxy cluster within the WORLD, as a result of lack of protecting halos of darkish matter on this mannequin,” he mentioned. Dr Indranil Banik from the College of St Andrews. “However our outcomes present outstanding settlement between observations and MOND expectations for the extent of disruption of Fornax dwarfs.”

“It’s thrilling to see that the information now we have obtained with the VLT telescope has allowed such thorough testing of cosmological fashions,” mentioned Aku Venhola from the College of Oulu (Finland) and Steffen Mieske from the European Observatory. austral, co-authors of the research.

This isn’t the primary time {that a} research testing the impact of darkish matter on the dynamics and evolution of galaxies has concluded that observations are finest defined when they don’t seem to be surrounded by darkish matter. “The variety of publications displaying incompatibilities between observations and the darkish matter paradigm retains rising yearly. It is time to begin investing extra sources in additional promising theories,” mentioned Pavel Kroupa, member of the transdisciplinary analysis areas modeling and matter on the College. from Bonn.

Dr Hongsheng Zhao from the College of St Andrews added that “their findings have main implications for elementary physics. We look forward to finding extra perturbed dwarfs in different clusters, a prediction that different groups ought to confirm. “.