Host Dependence and Line-of-Sight Effects on Galaxy-Galaxy Strong Lensing in Clusters
Abstract
The cross section for galaxy-galaxy strong lensing (GGSL) events in galaxy clusters has repeatedly been found to be higher in observations than in cosmological simulations. We revisit this discrepancy using updated simulation methodology and investigate the dependence of the GGSL probability, PGGSL, on host-cluster lensing properties, baryonic physics, and correlated and uncorrelated line-of-sight structure. We find that correlated material within ∼ 35 cMpc of the cluster along the line of sight enhances PGGSL by a few percent for typical systems and by up to ∼15% for the most efficient lenses. At fixed cluster mass, dark-matter-only simulations yield GGSL probabilities up to an order of magnitude lower than hydrodynamical simulations. We also find a strong dependence on the host-cluster Einstein radius, with an approximate scaling PGGSL ∝ θE2. Matching simulated and observed clusters in both mass and Einstein radius seems to reduce the discrepancy relative to previous comparisons. However, our analysis does not clearly resolve the GGSL discrepancy, as the inferred tension depends strongly on the field-of-view definition: square fields are approximately consistent with simulations, while cluster member-bounded fields yield observed probabilities a factor of ∼ 2−3 higher. Until observations and simulations share a matched selection function and matched measurement methodology, the residual tension cannot be cleanly attributed to either astrophysics or cosmology.
Related
- Constraining the Inner Dark Matter Profiles of Strong-Lensing Galaxy Clusters
- Late-time distance consistency and model-independent curvature inference with strong lensing, quasars, and galaxy clusters
- Observation-driven simulations of strong lensing galaxy clusters
- CHEX-MATE: AMALGAM weak-lensing analysis of 41 Planck Sunyaev--Zel'dovich-selected galaxy clusters
- Lensing in the Blue. III. Weak-lensing Shape Catalogs of 30 Merging Galaxy Clusters
BibTeX
@misc{roche2026host,
title = {{Host Dependence and Line-of-Sight Effects on Galaxy-Galaxy Strong Lensing in Clusters}},
author = {Cian Roche and Michael McDonald and Priyamvada Natarajan and Keren Sharon and Isaque Dutra and Massimo Meneghetti and Mark Vogelsberger},
howpublished = {arXiv},
year = {2026},
month = aug,
doi = {10.48550/arxiv.2608.30079},
eprint = {2608.30079},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2608.30079},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Host Dependence and Line-of-Sight Effects on Galaxy-Galaxy Strong Lensing in Clusters
AU - Cian Roche
AU - Michael McDonald
AU - Priyamvada Natarajan
AU - Keren Sharon
AU - Isaque Dutra
AU - Massimo Meneghetti
AU - Mark Vogelsberger
PY - 2026
DA - 2026/08/30
PB - arXiv
DO - 10.48550/arxiv.2608.30079
UR - https://arxiv.org/abs/2608.30079
AB - The cross section for galaxy-galaxy strong lensing (GGSL) events in galaxy clusters has repeatedly been found to be higher in observations than in cosmological simulations. We revisit this discrepancy using updated simulation methodology and investigate the dependence of the GGSL probability, P_GGSL, on host-cluster lensing properties, baryonic physics, and correlated and uncorrelated line-of-sight structure. We find that correlated material within ∼ 35 cMpc of the cluster along the line of sight enhances P_GGSL by a few percent for typical systems and by up to ∼15% for the most efficient lenses. At fixed cluster mass, dark-matter-only simulations yield GGSL probabilities up to an order of magnitude lower than hydrodynamical simulations. We also find a strong dependence on the host-cluster Einstein radius, with an approximate scaling P_GGSL ∝ θ_E^2. Matching simulated and observed clusters in both mass and Einstein radius seems to reduce the discrepancy relative to previous comparisons. However, our analysis does not clearly resolve the GGSL discrepancy, as the inferred tension depends strongly on the field-of-view definition: square fields are approximately consistent with simulations, while cluster member-bounded fields yield observed probabilities a factor of ∼ 2−3 higher. Until observations and simulations share a matched selection function and matched measurement methodology, the residual tension cannot be cleanly attributed to either astrophysics or cosmology.
ER -