2026-08-27 ワシントン大学（UW）
Most galaxies are likely surrounded by long filaments of orbiting stars known as stellar streams. In a new study from the University of Washington, astronomers simulated stellar streams — pictured here as multicolored streaks — as they orbited virtual host galaxies to test a leading theory about how dark matter might influence the streams’ shape. The results could help researchers separate true evidence of dark matter from false positives. Credit: Visualization by Arpit Arora and Adrian Price-Whelan. Milky Way image credit: Stefan Payne-Wardenaar.
＜関連情報＞
- https://www.washington.edu/news/2026/08/27/stellar-streams-dark-matter-simulation/
- https://iopscience.iop.org/article/10.3847/1538-4357/ae89af
流れは無傷ではいられない：宿主銀河の痕跡 No Stream Left Unscathed: The Imprint of a Host Galaxy
Arpit Arora, Peter S. Ferguson, Jacob Nibauer, Nora Shipp, Videep Reddy, Eugene Vasiliev, Jack Kohm, Laurella C. Marin, Adrian M. Price-Whelan, Denis Erkal,…
The Astrophysical Journal Published: 2026 August 27
DOI:10.3847/1538-4357/ae89af
Abstract
Stellar streams from disrupted globular clusters are excellent probes of dark matter (DM) subhalos. Observed Milky Way streams display a remarkable diversity of features: spurs, gaps, kinks, cocoons, and density variations, many attributed to subhalo encounters. But how much of this diversity arises from the host itself? We simulate ∼15,000 globular cluster streams across four Milky Way–mass halos from the FIRE-2 cosmological simulations, evolved in basis-function expansion potentials capturing the evolving disk, halo, and large-scale structure while excluding small-scale perturbers such as DM subhalos and giant molecular clouds. We find that roughly three-quarters of streams develop complex features from the host potential, such as spurs, kinks, and cocoon-like envelopes. Even the smoothest streams exhibit 10%–25% width variation along their track and host overdensities and gaps at scales of ∼2°, squarely in the 1°–5° range predicted for subhalo-induced gaps. Pericentric distance is the primary predictor of stream morphology, with ∼15 kpc separating smooth from disturbed streams and circular orbits beyond ∼20 kpc producing the smoothest streams. Only ∼70 out of ∼15,000 streams are free of detectable wiggles in the track at any scale. Analogs to observed features, such as the GD-1 spur and the ATLAS–Aliqa Uma kink, emerge even without the presence of subhalos. As next-generation surveys (LSST, Euclid, and the Nancy Grace Roman Space Telescope) resolve stream structure across hundreds of streams, the baseline established here, i.e., streams evolved without small-scale perturbers, becomes essential for extracting DM substructure constraints.
