of Hubble Space Telescope has shown that dark matter is centered within the core of a nearby dwarf galaxy, a discovery that hastened to save the standard model of cosmology. This model basically predicts dark matter to be “cold”, but recent findings have begun to hint that the substance is “warm”. These new observations, however, side with the Standard Model.
Dark matter is the invisible substance that is supposed to be composed of 85% of the mass of the universe, but no one knows what dark matter actually is, or exactly how it behaves. Our best guess is that it’s “cold,” which, in other words, means it’s predicted to consist of a low-energy particle that doesn’t bounce around, but is slow enough to be able to clumps together to form large halos within which galaxies grow. The concept of cold dark matter (CDM) and its influence on structure formation in UNIVERSE it is a critical part of our stream The standard model of cosmology. This part is known as Lambda–CDM (lambda refers to dark energy).
In the cold dark matter paradigm, dark matter should be particularly concentrated at the core of a dark matter halo, so dark matter should be denser at the core of a galaxy that grows within that halo. Astronomers call this dark matter a “cusp” because of the shape it makes on a plot of dark matter density versus its radius from the center of a galaxy.
However, astronomers have been surprised by some recent observations of dwarf galaxies that have hinted that dark matter may behave differently than they thought. Rather than acting as cool dark matter and clumping more densely at the core of the dark matter halo, these observations imply that dark matter may be more evenly distributed throughout a galaxy. This would be a sign that dark matter is “warm” or has enough energy for it NO I accumulate so much. If true, this would have important consequences for our cosmological models that rely on the ability of dark matter to clump together in certain ways.
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Now, astronomers led by Eduardo Vitral of the Space Telescope Science Institute (STScI) in Baltimore, Maryland, have put this to the test.
Dwarf galaxies are the best place to study dark matter because, proportionally, they have the largest amount of dark matter of any type of galaxy. The dwarf galaxy Draco, which was chosen for this study, orbits ours The Milky Way Galaxy at a distance of 250,000 light years from earth. In the Hubble archives, there is data describing the motions of the stars in the Draco dwarf spanning 18 years, between 2004 and 2022. Vitral’s team was able to use these motions to calculate a precise measurement of the dwarf’s gravitational field Draco, and thus the distribution of its mass, including the part dedicated to dark matter.
By combining the “right moves” of STARS – that is, their movement across the sky – with their radial movements towards or away from us being distinguished as one blue shift or a red shift in the light, Vitral’s team was able to track the movements of the stars in the Draco dwarf at 3D.
“When you measure proper motions, you note the position of a star at one epoch, and then many years later you measure the position of the same star. You measure the displacement to determine how much it moved,” said Sangmo team member Tony Sohn of STScI. in one STATEMENT. “For this kind of observation, the longer you wait, the better you can measure the motion of the stars.”
Of course, Hubble’s lifetime in ROOM is an advantage here, as is its powerful resolution from its high vantage point Earth’s turbulent atmosphere. The proper motion of the Draco dwarf stars over 18 years at a distance of a quarter of a million light-years is tiny, equal to less than the width of a golf ball in MONDAY as seen from Earth. Therefore, Hubble’s results are the most detailed measurements of the motions of stars in another galaxy ever made.
Using these stellar motions, the Vitral team concluded that the total mass of the Draco dwarf dark matter halo, at a radius of about 3,000 light years, is 120 million times mass of our sun. Furthermore, the results strongly indicate that the dark matter density profile of the Draco dwarf has a peak in the core and hence the dark matter IS maybe cold. As the researchers write in their research paper, “The results reduce the tension around the cusp-core problem and lend more credence to the standard lambda-CDM cosmology.”
“Our models tend to agree more with a spike-like structure, which is consistent with cosmological models,” Vitral said in the statement. “While we cannot definitively say that all galaxies contain a spike-like distribution of dark matter, it is exciting to have such well-measured data that surpasses anything we have had before.”
The next step, then, is to repeat the analysis for other dwarf galaxies, and the Vitral team is currently working on studies of the dwarf galaxies Sculptor and Ursa Minor, which also orbit our own Milky Way galaxy.
If the findings can be replicated in those and other galaxies, it would effectively rule out some dark matter candidates such as sterile neutrinos AND gravitatingthe latter is a hypothetical particle predicted by the theory of supersymmetry as the equally hypothetical mass partner (but maybe real) gravitates. The results therefore strengthen possible models of cold dark matter, mainly weakly interacting massive particles (WIMPs), primordial black holes AND Actions.
The results from the Draco dwarf were published on July 11 at The Astrophysical Journal.