Physicists propose new insights into dark matter through stellar streams

Physicists propose new insights into dark matter through stellar streams
by Clarence Oxford
Los Angeles CA (SPX) Jan 07, 2025

Researchers have identified a potential explanation for the unusual features of the GD-1 stellar stream, one of the most thoroughly studied stellar streams in the Milky Way's galactic halo. This thin, elongated stream exhibits distinctive spur and gap characteristics that have puzzled scientists. A team led by Professor Hai-Bo Yu from the University of California, Riverside, suggests these features may result from a core-collapsing self-interacting dark matter (SIDM) subhalo, a dense satellite halo within the Milky Way's galactic halo.

The findings, published in The Astrophysical Journal Letters, could deepen our understanding of dark matter, a mysterious component thought to comprise 85% of all matter in the universe. Stellar streams, which are groups of stars traveling together along a shared path, are influenced by dark matter, making them valuable tools for studying this enigmatic substance. Features such as gaps and spurs within these streams provide crucial clues about the distribution and behavior of dark matter in a galaxy.

The Milky Way's galactic halo, a roughly spherical region extending beyond the galaxy's visible edge, contains both dark matter and known stellar streams. Scientists have determined that the spur and gap features in the GD-1 stellar stream cannot be easily explained by gravitational forces from globular clusters or satellite galaxies. However, these peculiarities align with the presence of a previously unidentified perturbing object-a dense subhalo.

"CDM subhalos typically lack the density needed to produce the distinctive features observed in the GD-1 stream," explained Yu, a professor of physics and astronomy. "However, our research demonstrates that a collapsing SIDM subhalo could achieve the necessary density. Such a compact subhalo would be dense enough to exert the gravitational influence required to account for the observed perturbations in the GD-1 stream."

Unlike traditional cold dark matter (CDM), which assumes dark matter particles do not interact, SIDM theories propose that these particles can interact with one another via a new dark force. To test their hypothesis, Yu's team employed advanced N-body simulations to replicate the behavior of a collapsing SIDM subhalo.

"Our team's findings offer a new explanation for the observed spur and gap features in GD-1, which have long been thought to indicate a close encounter with a dense object," Yu said. "In our scenario, the perturber is the SIDM subhalo, which disrupts the spatial and velocity distributions of the stars in the stream and creates the distinctive features we see in the GD-1 stellar stream."

The study not only sheds light on the properties of dark matter but also highlights the potential of stellar streams as a method for investigating galactic dynamics. "This work opens a promising new avenue for investigating the self-interacting properties of dark matter through stellar streams," Yu added. "It marks an exciting step forward in our understanding of dark matter and the dynamics of the Milky Way."

The research was supported by the U.S. Department of Energy and the John Templeton Foundation. Collaborators include Xingyu Zhang and Daneng Yang from UC Riverside, and Ethan O. Nadler from UC San Diego.

Research Report:The GD-1 Stellar Stream Perturber as a Core-collapsed Self-interacting Dark Matter Halo