A new study challenges past theories, suggesting the ultra-diffuse galaxy NGC 1052-DF2 may have dark matter, just spread out more evenly across the galaxy.
Ordinary, or baryonic, matter including everything we can see, such as Earth, the Sun, stars, and galaxies makes up less than 5 per cent of the universe's total mass-energy content. The remaining 25 per cent is dark matter, while roughly 70 per cent is dark energy a force that counteracts gravity. Both are invisible and not yet fully understood.
Dark matter is believed to dominate the universe. This invisible substance is said to make up most of its mass and interacts only through gravity not through light or physical contact. It's called 'dark' because it emits no light or energy, yet its gravitational pull is crucial. Dark matter plays a crucial role in galaxy formation and evolution. A galaxy can be assumed as a merry-go-round where the lights and horses are the stars. If it spins too fast, everything should fly off unless there's extra invisible weight keeping it grounded. That weight is dark matter. Visible galaxies emerge within these dark matter halos as gas falls inward and condenses. When the gas becomes dense enough, star formation begins, giving rise to the galaxies.
In this context, the ultra-diffuse galaxy (UDG) NGC 1052-DF2 has long baffled astronomers due to its apparent deficiency in dark matter. This deficiency poses a significant challenge to the standard cosmological model, which relies on dark matter to explain the large-scale structure of the universe.
A recent study titled "Challenges in modelling the dark matter halo of NGC 1052–DF2: Cored versus cuspy halo models" by K Aditya, a postdoctoral researcher at the Indian Institute of Astrophysics (IIA), offers a compelling reinterpretation of these findings. The research study, published in Astronomy and Astrophysics (2024), delves into the structural modelling of the galaxy's dark matter halo.
The mystery of galaxy NGC 1052-DF2
In an exclusive interview with ETV Bharat's Anubha Jain, Aditya talked in detail about his research work. He said, "I studied an ultra-diffuse galaxy called NGC 1052-DF2, which is located about 62 million light-years away. These galaxies are unusual as they are very large but contain very few stars, so they appear extremely faint and spread out."
He said earlier studies suggested that NGC 1052-DF2 might have almost no dark matter. That's surprising, because dark matter is usually thought to be essential for holding galaxies together. According to those studies, the total mass of this galaxy is around 340 million times the mass of our Sun, while the stars themselves make up about 200 million solar masses, which means most of the mass seems to come from baryonic matter like stars, and very little, if any, from dark matter.
"This goes against our current understanding of how galaxies form and behave," he added. "The dark matter in the galaxy depends a lot on the assumptions we make about the shape and structure of the dark matter 'halo'—the invisible cloud of dark matter that surrounds galaxies and the available kinematic data. I used a statistical technique called Markov Chain Monte Carlo (MCMC) to test different models and find out which ones best match the real observations of how stars move within the galaxy."
He said that galaxies form when gas falls into big clumps of dark matter, called dark matter halos, and starts forming stars. At first, these dark matter halos are thought to be dense in the centre we call that a "cuspy" shape. As the galaxy evolves, powerful events like supernova explosions and activity around black holes can push against the dark matter and make it spread out more evenly, turning the centre into a flatter, "cored" shape.
Models with a sharp, dense centre of dark matter (called "cuspy" halos) don't fit the data well these models were no better than assuming there's no dark matter at all. They couldn't explain how stars behave in the outer parts of the galaxy. But models with a large dark matter core where the dark matter is more evenly spread out fit the observations much better. In these models, the galaxy contains about 10 times more dark matter than stars, which matches what current galaxy formation theories expect. So even though NGC 1052-DF2 looks strange because of how few stars it has, the results suggest it may still have a normal amount of dark matter just spread out very diffusely, like its stars. This means it might not be so unusual after all, and still fits within the standard picture of how galaxies form in the universe, Aditya mused.
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Ordinary, or baryonic, matter including everything we can see, such as Earth, the Sun, stars, and galaxies makes up less than 5 per cent of the universe's total mass-energy content. The remaining 25 per cent is dark matter, while roughly 70 per cent is dark energy a force that counteracts gravity. Both are invisible and not yet fully understood.
Dark matter is believed to dominate the universe. This invisible substance is said to make up most of its mass and interacts only through gravity not through light or physical contact. It's called 'dark' because it emits no light or energy, yet its gravitational pull is crucial. Dark matter plays a crucial role in galaxy formation and evolution. A galaxy can be assumed as a merry-go-round where the lights and horses are the stars. If it spins too fast, everything should fly off unless there's extra invisible weight keeping it grounded. That weight is dark matter. Visible galaxies emerge within these dark matter halos as gas falls inward and condenses. When the gas becomes dense enough, star formation begins, giving rise to the galaxies.
In this context, the ultra-diffuse galaxy (UDG) NGC 1052-DF2 has long baffled astronomers due to its apparent deficiency in dark matter. This deficiency poses a significant challenge to the standard cosmological model, which relies on dark matter to explain the large-scale structure of the universe.
A recent study titled "Challenges in modelling the dark matter halo of NGC 1052–DF2: Cored versus cuspy halo models" by K Aditya, a postdoctoral researcher at the Indian Institute of Astrophysics (IIA), offers a compelling reinterpretation of these findings. The research study, published in Astronomy and Astrophysics (2024), delves into the structural modelling of the galaxy's dark matter halo.
The mystery of galaxy NGC 1052-DF2
In an exclusive interview with ETV Bharat's Anubha Jain, Aditya talked in detail about his research work. He said, "I studied an ultra-diffuse galaxy called NGC 1052-DF2, which is located about 62 million light-years away. These galaxies are unusual as they are very large but contain very few stars, so they appear extremely faint and spread out."
He said earlier studies suggested that NGC 1052-DF2 might have almost no dark matter. That's surprising, because dark matter is usually thought to be essential for holding galaxies together. According to those studies, the total mass of this galaxy is around 340 million times the mass of our Sun, while the stars themselves make up about 200 million solar masses, which means most of the mass seems to come from baryonic matter like stars, and very little, if any, from dark matter.
"This goes against our current understanding of how galaxies form and behave," he added. "The dark matter in the galaxy depends a lot on the assumptions we make about the shape and structure of the dark matter 'halo'—the invisible cloud of dark matter that surrounds galaxies and the available kinematic data. I used a statistical technique called Markov Chain Monte Carlo (MCMC) to test different models and find out which ones best match the real observations of how stars move within the galaxy."
He said that galaxies form when gas falls into big clumps of dark matter, called dark matter halos, and starts forming stars. At first, these dark matter halos are thought to be dense in the centre we call that a "cuspy" shape. As the galaxy evolves, powerful events like supernova explosions and activity around black holes can push against the dark matter and make it spread out more evenly, turning the centre into a flatter, "cored" shape.
Models with a sharp, dense centre of dark matter (called "cuspy" halos) don't fit the data well these models were no better than assuming there's no dark matter at all. They couldn't explain how stars behave in the outer parts of the galaxy. But models with a large dark matter core where the dark matter is more evenly spread out fit the observations much better. In these models, the galaxy contains about 10 times more dark matter than stars, which matches what current galaxy formation theories expect. So even though NGC 1052-DF2 looks strange because of how few stars it has, the results suggest it may still have a normal amount of dark matter just spread out very diffusely, like its stars. This means it might not be so unusual after all, and still fits within the standard picture of how galaxies form in the universe, Aditya mused.
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Get Connected Here:
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Twitter : x.com/Psciencefather
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Blog : physicscience23.blogspot.com
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