of Hubble Space Telescope teeth, Dark matter Concentrated in the centre of a nearby dwarf galaxy, this is a discovery that saves the standard model of the galaxy. CosmologyThis model essentially predicts that dark matter is “cold,” but recent findings are beginning to suggest that this matter is “warm.” However, these new observations favor the Standard Model.
Dark matter is an invisible substance that is believed to make up the universe. 85% of the mass of the universeBut no one knows what dark matter actually is, or how it behaves. Our best guess is that it’s “cold.” In other words, it’s predicted to be made up of low-energy particles that don’t fly around everywhere, but rather move slowly and come together to form giant halos within which galaxies grow. The concept of cold dark matter (CDM) and its impact on the formation of structure in the universe is a mystery. The Universe It’s an important part of our current situation. Standard Model This part of the cosmology is known as lambda CDM (lambda stands for Dark Energy).
In the cold dark matter paradigm, dark matter should be particularly accumulated in the central core of a dark matter halo, and therefore dark matter should be most dense in the central core. Galaxy It grows inside the halo, and astronomers call it the dark matter “cusp” because they plot its shape on a graph of dark matter density versus radius from the galaxy’s center.
But astronomers are puzzled by recent observations of dwarf galaxies that suggest dark matter may behave differently than they thought. These observations suggest that dark matter may behave like cold dark matter, not being most densely concentrated in the center of a dark matter halo, but rather being more evenly distributed throughout the galaxy. This is a sign that the dark matter is “warm,” that is, has enough energy to be able to move around freely. do not have Dark matter has never been more clumped together than this, and if this were true, it would have significant implications for our cosmological models, which assume that dark matter can clump together in a particular way.
Astronomers led by Eduardo Vitral at the Space Telescope Science Institute (STScI) in Baltimore, Maryland, are currently testing it.
Dwarf galaxies are the perfect place to study dark matter because they have the highest dark matter content of any galaxy type. The Draco dwarf galaxy chosen for this study orbits our own Milky Way Galaxy. Milky Way Galaxy 250,000 light years away EarthThe Hubble Space Telescope archives contain data describing the stellar motion of the Draco dwarf over an 18-year period, from 2004 to 2022. Using these motions, Vitral’s team was able to calculate precise measurements of the Draco dwarf’s gravitational field and calculate the distribution of its mass, including its fraction of dark matter.
By combining “appropriate movements”, Performer That is, their movement across the sky, their radial movement towards or away from us, Blueshift or Redshift In the light, Vitral’s team was able to track the movement of the Draco dwarf star. 3D.
“When we measure proper motion, we record the position of a star at a point in time and then measure the position of the same star many years later. By measuring its displacement, we determine how much it has moved,” said Sangmo Tony Song, team member from STScI. statement“With these types of observations, the longer we wait, the more precisely we can measure the movement of the star.”
Indeed, Hubble’s longevity space The high resolution from a high position is also an advantage here. Earth’s turbulent atmosphereThe Draco dwarf, located 250,000 light-years away, has a proper motion every 18 years that is smaller than the width of a golf ball. Moon Viewed from EarthHubble’s results therefore provide the most detailed measurements yet of the motions of stars in another galaxy.
Vitral’s team used the motions of these stars to determine that the total mass of the Draco dwarf’s dark matter halo, spanning a radius of about 3,000 light years, is Mass of the SunFurthermore, the results strongly suggest that the dark matter density profile of the Draco dwarf has a cusp at its core, and therefore dark matter is teeth Cold, perhaps. “Our results ease tensions regarding the ‘cusp core’ problem and lend further credence to standard Lambda-CDM cosmology,” the researchers wrote in their study.
“Our model tends to match a cusp-shaped structure that is consistent with cosmological models,” Vitral said in a statement. “While we cannot say with certainty that all galaxies have cusp-shaped dark matter distributions, it is exciting to have such well-measured data that is better than anything we’ve had to date.”
So the next step is to repeat the analysis with other dwarf galaxies, and Vitral’s team is currently studying the Polycephalus and Ursa Minor dwarf galaxies, which orbit the Milky Way.
Similar discoveries in these and other galaxies would effectively rule out the following dark matter candidates: Sterile Neutrino and GravitinosThe latter are hypothetical particles predicted by the theory. Supersymmetry Similarly, hypothetical (but probably Real) GravitonThe results strengthen models of cold dark matter, predominantly weakly interacting massive particles (WIMPs), and primordial dark matter. Black Hole and Axion.
The Draco dwarf results were announced on July 11th. Astrophysical Journal.
