Extragalactic Stellar Streams in Time-Dependent Cosmological Halos
Abstract
Upcoming and ongoing surveys will detect thousands of stellar streams around galaxies other than the Milky Way. Studies from the Milky Way have shown that time-dependent evolution of the Galactic halo plays a key role in shaping stellar streams, but remains unexplored for extragalactic stellar streams. We use the FIRE-2 m12m cosmological zoom-in simulation, mock observed as an extragalactic system including three stellar streams, to examine how halo time-dependence affects progenitor and host halo inference from extragalactic systems. We show that two of the three m12m streams are well reproduced in a static halo if we only allow for tidal stripping near pericenter. We apply the extragalactic stream fitting code X-Stream to each mock observed stream, and obtain constraints on the host dark matter halo and stream properties. Using on-sky morphology alone and then fixing the progenitor radial velocities, we compare recovered orbits and halo parameters to the FIRE-2 m12m ground truth. For the longest stream with a looped segment, we find unbiased strong constraints on progenitor and halo properties. For the shortest stream, we find limits on orbital parameters, but no constraints on progenitor and halo mass unless we include fainter, more extended debris. For the most massive stream, which was not well produced in a static halo, the recovered orbital parameters are biased, reflecting unmodeled time-dependence. We conclude that imaging of stream debris from extragalactic dwarf galaxies can, in some cases, be used to infer present-day dark matter halo properties, even in a cosmological environment.
Related
- When Streams Curve Away: a Test of Dark Matter from Extragalactic Stellar Stream Populations
- Dark Halos, Intermediate-Mass BH and Nuclear Stellar Clusters in Dwarf Spheroidals
- The multiple origins of spurs in stellar streams: a challenge for dark matter diagnostics
- Dark Matter in the Galaxy: Insights from the Dynamics of Stellar Streams
- Stellar streams around dwarf galaxies are observationally rare in the local Universe
BibTeX
@misc{pearson2026extragalactic,
title = {{Extragalactic Stellar Streams in Time-Dependent Cosmological Halos}},
author = {Sarah Pearson and Jacob Nibauer and Emily C. Cunningham and Adrian M. Price-Whelan and Adrien C. R. Thob and Arpit Arora and Robyn E. Sanderson},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.00526},
eprint = {2609.00526},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.00526},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Extragalactic Stellar Streams in Time-Dependent Cosmological Halos
AU - Sarah Pearson
AU - Jacob Nibauer
AU - Emily C. Cunningham
AU - Adrian M. Price-Whelan
AU - Adrien C. R. Thob
AU - Arpit Arora
AU - Robyn E. Sanderson
PY - 2026
DA - 2026/09/01
PB - arXiv
DO - 10.48550/arxiv.2609.00526
UR - https://arxiv.org/abs/2609.00526
AB - Upcoming and ongoing surveys will detect thousands of stellar streams around galaxies other than the Milky Way. Studies from the Milky Way have shown that time-dependent evolution of the Galactic halo plays a key role in shaping stellar streams, but remains unexplored for extragalactic stellar streams. We use the FIRE-2 m12m cosmological zoom-in simulation, mock observed as an extragalactic system including three stellar streams, to examine how halo time-dependence affects progenitor and host halo inference from extragalactic systems. We show that two of the three m12m streams are well reproduced in a static halo if we only allow for tidal stripping near pericenter. We apply the extragalactic stream fitting code X-Stream to each mock observed stream, and obtain constraints on the host dark matter halo and stream properties. Using on-sky morphology alone and then fixing the progenitor radial velocities, we compare recovered orbits and halo parameters to the FIRE-2 m12m ground truth. For the longest stream with a looped segment, we find unbiased strong constraints on progenitor and halo properties. For the shortest stream, we find limits on orbital parameters, but no constraints on progenitor and halo mass unless we include fainter, more extended debris. For the most massive stream, which was not well produced in a static halo, the recovered orbital parameters are biased, reflecting unmodeled time-dependence. We conclude that imaging of stream debris from extragalactic dwarf galaxies can, in some cases, be used to infer present-day dark matter halo properties, even in a cosmological environment.
ER -