Impact of LSST systematics on stellar-stream density fluctuations for dark matter
Abstract
The Vera C. Rubin Observatory's Legacy Survey of Space and Time (LSST) is expected to significantly advance the study of Milky Way stellar streams. In particular, the deep, precise photometry from LSST should greatly increase the statistical sensitivity to density fluctuations in stellar streams, which can be used to probe the small-scale distribution of dark matter. However, current forecasts generally neglect the impact of observational systematics that will be imprinted on stream density measurements. In this study, we develop a realistic forward-modeling framework to inject stellar streams into LSST-like observations including photometric uncertainties, survey depth variations, background contamination, and imperfect star-galaxy classification. We develop a likelihood-ratio analysis to assess the detectability of gaps in stellar streams in the presence of these observational systematics. In the presence of realistic survey systematics, we find that after four years of operations, LSST will be sensitive to density reductions of ∼50% for gaps with widths of $5$ deg in streams with surface brightness of ∼33 mag arcsec−2. Relative to the ideal case, this corresponds to a degradation in gap depth sensitivity by a factor of ∼5 due to the combined impact of background contamination and observational systematics. Assuming a simplified analytical mapping between gap depth and dark matter subhalo properties, these estimates correspond to a minimum detectable subhalo mass of ∼1×107 M⊙. Observational effects shift this accessible mass scale upward by a factor of ∼16, with background contamination contributing a factor of ∼5 and survey systematics a further factor of ∼3, dominated by star-galaxy classification.
Related
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- Enhanced density fluctuations: consequences for stellar dynamics and dark matter substructure
- When Streams Curve Away: a Test of Dark Matter from Extragalactic Stellar Stream Populations
- Potamides: Mapping Dark Matter Halo Shapes from Stellar Stream Tracks in the Local Universe
- Evidence for the First Globular Cluster Stellar Stream beyond the Milky Way
BibTeX
@misc{pelissier2026impact,
title = {{Impact of LSST systematics on stellar-stream density fluctuations for dark matter}},
author = {Matthieu Pélissier and Peter S Ferguson and Alex Drlica-Wagner and Marine Kuna and David Maurin and Christian Aganze and Johann Cohen-Tanugi and Yao-Yuan Mao},
howpublished = {HAL},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.10897},
eprint = {2609.10897},
archivePrefix = {arXiv},
url = {https://hal.science/hal-05759394v1},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Impact of LSST systematics on stellar-stream density fluctuations for dark matter
AU - Matthieu Pélissier
AU - Peter S Ferguson
AU - Alex Drlica-Wagner
AU - Marine Kuna
AU - David Maurin
AU - Christian Aganze
AU - Johann Cohen-Tanugi
AU - Yao-Yuan Mao
PY - 2026
DA - 2026/09/09
PB - HAL
DO - 10.48550/arxiv.2609.10897
UR - https://hal.science/hal-05759394v1
AB - The Vera C. Rubin Observatory's Legacy Survey of Space and Time (LSST) is expected to significantly advance the study of Milky Way stellar streams. In particular, the deep, precise photometry from LSST should greatly increase the statistical sensitivity to density fluctuations in stellar streams, which can be used to probe the small-scale distribution of dark matter. However, current forecasts generally neglect the impact of observational systematics that will be imprinted on stream density measurements. In this study, we develop a realistic forward-modeling framework to inject stellar streams into LSST-like observations including photometric uncertainties, survey depth variations, background contamination, and imperfect star-galaxy classification. We develop a likelihood-ratio analysis to assess the detectability of gaps in stellar streams in the presence of these observational systematics. In the presence of realistic survey systematics, we find that after four years of operations, LSST will be sensitive to density reductions of ∼50% for gaps with widths of $5$ deg in streams with surface brightness of ∼33 mag arcsec^−2. Relative to the ideal case, this corresponds to a degradation in gap depth sensitivity by a factor of ∼5 due to the combined impact of background contamination and observational systematics. Assuming a simplified analytical mapping between gap depth and dark matter subhalo properties, these estimates correspond to a minimum detectable subhalo mass of ∼1×10^7 M_⊙. Observational effects shift this accessible mass scale upward by a factor of ∼16, with background contamination contributing a factor of ∼5 and survey systematics a further factor of ∼3, dominated by star-galaxy classification.
ER -