Galaxy Formation: IIA study decodes the curious case of missing dark matter from distant galaxy | India News

Image of extremely diffuse galaxy “NGC 1052 – DF2”, taken by the ACS/WFC instrument on the Hubble Space Telescope. (Picture credit score: DST)

A distant galaxy as soon as thought to lack a key ingredient in galaxy formation could now be higher understood, due to new analysis from Bengaluru’s Indian Institute of Astrophysics (IIA).
Their latest study, printed in Astronomy & Astrophysics, revisits the puzzling case of “NGC 1052-DF2” — a galaxy 62 million mild years away and gives a recent clarification for its obvious scarcity of dark matter.
“NGC 1052-DF2” belongs to a category of galaxies known as ultra-diffuse galaxies (UDGs). These are faint, spread-out collections of stars with comparatively few of them for his or her dimension. Unlike the dense spiral arms of our Milky Way, UDGs reminiscent of “NGC 1052-DF2” seem ghostly and sparse, virtually translucent towards the backdrop of area.
What made DF2 significantly intriguing was its seemingly low content material of dark matter. Earlier research estimated the complete ‘dynamical mass’ — the sum of all matter influencing its gravitational behaviour — to be round 340 million instances the mass of the Sun.
“That figure was not far off from the estimated 200 million solar masses contained in visible stars alone, implying that dark matter, which usually makes up the bulk of a galaxy’s mass, was largely absent. This finding challenged prevailing theories, as dark matter is thought to play a central role in galaxy formation and structure,” the division of science and know-how (DST) stated.
But the new study led by Okay Aditya from IIA, which is an autonomous institute underneath DST, gives a special take.
“We find that “NGC 1052-DF2” poses fascinating questions relating to the formation of galaxies with minimal dark matter content material, the astrophysical processes regulating the formation of such galaxies, in addition to the potential nature of dark matter itself,” stated Aditya.
To examine, Aditya developed detailed fashions of the galaxy’s mass utilizing the distribution of its stars and their noticed velocities. These fashions examined totally different assumptions about the construction of the galaxy’s dark matter halo—the huge, invisible cloud of matter thought to encompass galaxies and have an effect on their dynamics.
Interestingly, the study discovered that fashions with a concentrated, or “cuspy”, dark matter halo couldn’t clarify the noticed actions of stars in each the internal and outer elements of “NGC 1052-DF2”.
“We rule out the possibility of a cuspy dark matter halo for describing the mass models of NGC 1052 – DF2,” Aditya stated. Instead, the analysis helps a “cored” mannequin—one the place dark matter is unfold extra evenly by means of the galaxy’s centre.
According to the findings, a cored halo with a complete mass of about 32 billion photo voltaic plenty matches the noticed knowledge, although it could require an unusually prolonged construction: 65,000 mild years in scale size, with a cutoff at round 85,000 mild years.
“Our results suggest that ‘NGC 1052 – DF2’ may not only have an ultra-diffuse stellar distribution but that it can, within known uncertainties in the data, potentially host an ultra-diffuse dark matter distribution compatible with the standard galaxy formation and evolution models,” stated Aditya.
The work helps make clear a long-standing thriller and reveals how even galaxies that seem like outliers may nonetheless match into our broader understanding of the cosmos—as soon as we mannequin them fastidiously sufficient.