“The case of the missing dark matter” – Hubble solves a mystery



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Galaxy NGC1052-DF4

“The nature of dark matter is one of the biggest mysteries in science and we have to use all the new data related to it to deal with it,” says astronomer Avi Loeb of the Harvard-Smithsonian Center for Astrophysics. Dark matter is “dark” in that it hardly interacts with anything, especially light. While dark matter may be too elusive to be found in particle experiments, it can reveal its presence in astronomical observations.

At the frontiers of fundamental physics

Dark matter pushes the boundaries of known fundamental laws of physics. Leading candidates for dark matter who have so far challenged all types of detectors designed to find it. Due to its huge gravitational footprint in space, we know that dark matter must be around 85% of the total mass of the universe, but we don’t yet know what it’s made of, but if it has anything to do with it. to do with scalar particles. , it may be older than the Big Bang, suggest physicists who, sounding like sci-fi creators, imagined new types of dark matter ranging from particles the size of a planet to the life of matter. highly speculative black.

Hubble’s clues to missing dark matter

But what astrophysicists Know, is that new data from the Hubble Space Telescope explains the reason for the absence of dark matter in NGC 1052-DF4, which resides 45 million light-years from Earth. Astronomers have discovered that the missing enigmatic matter can be explained by the effects of tidal disturbance by gravity forces from the nearby massive galaxy NGC 1035 which strips NGC 1052-DF4 of dark matter. while the stars feel the effects of interacting with another galaxy at a later stage.

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Until now, the removal of dark matter in this way has remained hidden until astronomers using Hubble’s high resolution can observe extremely deep images that can reveal extremely faint features, including the identification of the population of globular clusters in the galaxy.

“We used Hubble in two ways to discover that NGC 1052-DF4 undergoes an interaction, this includes studying the light of the galaxy and the distribution of globular clusters in the galaxy,” STScI Fellow told Space Telescope Science Institute, Mireia Montes of the University of New South Wales in Australia, who led an international team of astronomers to study the galaxy using deep optical imagery, including the Gran Telescopio Canarias (GTC) telescope of 10 , 4 meters and the IAC80 telescope in the Canaries, Spain, to complement Hubble’s observations,

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This image at the top of the page shows the region around the galaxy NGC 1052-DF4, taken by the IAC80 telescope at the Teide Observatory in Tenerife. The figure highlights the main galaxies in the field of view, including NGC 1052-DF4 (center of image), and its neighbor NGC 1035 (center left).

Globular clusters reveal clues

Globular clusters – the oldest visible objects in the universe that are thought to have formed shortly after the Universe began almost 13.8 billion years ago, at the same time or perhaps even before the formation of the first galaxies. They are believed to form in the episodes of intense star formation that shaped galaxies. Each contains hundreds of thousands to sometimes more than ten million stars, all born essentially at the same time, and densely packed into a spherical volume with a diameter more than a thousand times smaller than the diameter of the Milky Way. Their compact dimensions and luminosity make them easily observable and they are therefore good tracers of the properties of their host galaxy.

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By studying and characterizing the spatial distribution of clusters in NGC 1052-DF4, astronomers can develop insight into the current state of the galaxy itself. The alignment of these clusters suggests that they are “stripped” of their host galaxy, supporting the conclusion that a tidal disturbance is occurring.

Tidal Tails Confirms Disruption Event

While studying the light of the galaxy, astronomers also found evidence of tidal tails, which are formed of material moving away from NGC1052-DF4 – this further supports the conclusion that this is a disruptive event. Further analysis concluded that the central parts of the galaxy remain intact and that only ∼ 7% of the galaxy’s stellar mass is hosted in these tidal tails. This means that dark matter, which is less concentrated than stars, was previously and preferentially cleared from the galaxy, and now the outer stellar component is starting to be as well.

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Stars showing effects after dark matter evaporates

“This result is a good indicator that, as the dark matter in the galaxy has evaporated from the system, the stars are only beginning to suffer from the disturbance mechanism,” said Ignacio Trujillo, member of the team. ‘Instituto de Astrofísica de Canarias in Spain. “Over time, NGC1052-DF4 will be cannibalized by the large system around NGC1035, with at least some of their stars floating freely in deep space.”

“A sigh of relief”

Finding evidence to support the tidal disturbance mechanism as an explanation for the galaxy’s missing dark matter has not only solved an astronomical conundrum, but also brought a sigh of relief to astronomers. Without it, scientists would be faced with the need to rethink our understanding of the laws of gravity.

“This discovery reconciles existing knowledge about how galaxies form and evolve with the most favorable cosmological model,” Montes added.

The Daily Galaxy, Max Goldberg, via ESA / Hubble Information Center



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