Strong Lensing Tomography: Double and pseudo multi-source plane strong gravitational lensing to constrain dark energy

@misc{sharma2026strong,
  title = {{Strong Lensing Tomography: Double and pseudo multi-source plane strong gravitational lensing to constrain dark energy}},
  author = {Paras Sharma and Simon Birrer and Narayan Khadka and Timo Anguita and Adam Bolton and Sydney Erickson and Phil Holloway and Tian Li and Phil Marshall and Dieu D. Nguyen and Graham P. Smith and Crescenzo Tortora and Bryce Wedig and the Strong Lensing Science Collaboration and the LSST Dark Energy Science Collaboration},
  howpublished = {arXiv},
  year = {2026},
  month = oct,
  doi = {10.48550/arxiv.2607.01005},
  eprint = {2607.01005},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2607.01005},
  note = {CC BY 4.0},
}

TY  - UNPB
TI  - Strong Lensing Tomography: Double and pseudo multi-source plane strong gravitational lensing to constrain dark energy
AU  - Paras Sharma
AU  - Simon Birrer
AU  - Narayan Khadka
AU  - Timo Anguita
AU  - Adam Bolton
AU  - Sydney Erickson
AU  - Phil Holloway
AU  - Tian Li
AU  - Phil Marshall
AU  - Dieu D. Nguyen
AU  - Graham P. Smith
AU  - Crescenzo Tortora
AU  - Bryce Wedig
AU  - the Strong Lensing Science Collaboration
AU  - the LSST Dark Energy Science Collaboration
PY  - 2026
DA  - 2026/10/23
PB  - arXiv
DO  - 10.48550/arxiv.2607.01005
UR  - https://arxiv.org/abs/2607.01005
AB  - Tomographic measurements of gravitational lensing with different lens and source redshift distributions contain crucial information about the universe's relative expansion rate, and hence dark energy. While this technique is well-established in weak lensing, its application to strong lensing has traditionally focused on Double Source Plane Lenses (DSPLs). However, DSPLs are exceedingly rare and fundamentally limited by the Mass-Sheet Degeneracy (MSD), a systematic uncertainty underexplored in previous literature. To overcome these challenges, we introduce Pseudo Double-Source Plane Lenses (PDSPLs): pairs of independent single-source plane lenses with self-similar deflectors. This generalizes the DSPL formalism to the ∼ 10^5 galaxy-galaxy lenses expected from LSST, Euclid, and Roman. Unlike true DSPLs, PDSPLs are free from the intermediate source mass problem by construction, eliminating the associated secondary MSD and the need for multi-plane ray tracing. We incorporate the deflector MSD into a hierarchical population model to forecast dark energy constraints in Flat w_0w_aCDM, showing that MSD severely degrades constraints from small DSPL samples and motivates our PDSPL statistical approach. Assuming unbiased Gaussian photo-z errors of σ_z/(1+z)=0.03, the mock LSST Y10 photometric sample yields σ(w_0)∼0.45, constraining the population-mean MSD parameter and deflector power-law slope to ∼2%. A prior Ω_m∼𝒩(0.3,0.05), representing combination with external cosmological probes such as CMB, BAO, or SNe Ia, improves this to σ(w_0)∼0.29, comparable to Stage III weak lensing. The statistical advantage over smaller spectroscopic subsets (e.g., 4MOST) assumes unbiased photo-zs. Real-data use requires spectroscopic photo-z calibration and validation of how paired deflectors' mass-profile differences affect Einstein-radius ratios.
ER  -