Researchers have advanced our understanding of dark matter through simulations that support the self-interacting dark matter (SIDM) theory. This theory has the potential to resolve the discrepancy in dark matter density observed in different galaxies, poses a challenge to traditional cold dark matter (CDM) models, and highlights the dynamic nature of dark matter. Credit: SciTechDaily.com
Dark matter may be more active than previously thought, reports a study from the University of California, Riverside.
Dark matter, which is thought to make up 85% of the matter in the universe, does not emit light and its properties are still poorly understood. Normal matter absorbs, reflects, and emits light, but dark matter cannot be seen directly, making it difficult to detect. A theory called “self-interacting dark matter” (SIDM) claims that dark matter particles self-interact with each other due to dark forces, causing them to collide strongly with each other near the centers of galaxies.
Among the works published in of Astrophysics Journal LetterA research team led by Haibo Yu, a professor of physics and astronomy at the University of California, Riverside, reports that SIDM can simultaneously explain two extreme astrophysical puzzles.
Understanding dark matter halos and gravitational lenses
“The first is a halo of dense dark matter in a giant elliptical galaxy,” Yu said. “The halo is detected by observations of strong gravitational lenses, and its density is so high that it is extremely unlikely under the prevailing cold dark matter theory. Second, the density of dark matter halos in superdiffuse galaxies is extremely low. is extremely low and difficult to explain using cold dark matter theory.”
A dark matter halo is an invisible halo of matter that permeates and surrounds a galaxy or galaxy cluster. Gravitational lensing occurs when light traveling across space from a distant galaxy is bent around a massive object. The cold dark matter (CDM) paradigm/theory assumes that dark matter particles do not collide. As the name suggests, superdiffuse galaxies have extremely low luminosity and a dispersed distribution of stars and gas.
Hai-Bo Yu is a theoretical physicist at the University of California, Riverside, with expertise in the particle properties of dark matter.Credit: Samantha Tiu
Yu was also joined in the study by Ethan Nadler, a postdoctoral fellow at the Carnegie Observatory and the University of Southern California, and Danen Yang, a postdoctoral fellow at UCR.
To show that SIDM can explain two puzzles in astrophysics, the research team presents a theory of cosmic structure formation with strong dark matter self-interactions at relevant mass scales for strong lenticular halos and superdiffuse galaxies. We conducted our first high-resolution simulation.
“These self-interactions cause heat transfer within the halo and diversify the halo density in the central region of the galaxy,” Nadler said. “In other words, some halos have higher center densities and others have lower center densities compared to their CDM counterparts, the details of which depend on the evolutionary history of the Universe and the environment of the individual halo.”
Challenges to the CDM paradigm and future research
According to the research team, these two puzzles pose a formidable challenge to the standard CDM paradigm.
“CDM takes on the challenge of explaining these mysteries,” Yang said. “SIDM is probably a good candidate for reconciling two opposing extremes. There are no other explanations in the literature. We now know that dark matter may be more complex and active than we expected. There is an interesting possibility that there is.”
The study also demonstrates the ability to investigate dark matter through astrophysical observations using computer simulation tools of cosmic structure formation.
“We hope that our study will encourage further research in this promising research area,” Yu said. “This is a particularly timely development given the expected influx of data in the near future from observatories such as the James Webb Space Telescope and the upcoming Rubin Observatory.”
Since around 2009, the work of Yu and his collaborators has popularized SIDM in the particle physics and astrophysics communities.
References: Ethan O. Nadler, Danen Yang, and Haibo Yu, “Self-interacting dark matter solutions for the extreme diversity of low-mass halo properties,” November 30, 2023. Astrophysics Journal Letter.
DOI: 10.3847/2041-8213/ad0e09
This research was supported by the John Templeton Foundation and the U.S. Department of Energy.
Source: scitechdaily.com
