An LSST-DESC Precursor Project: Hyper Suprime-Cam Year 1 3×2pt in Harmonic Space

Abstract

We present the first fully photometric joint analysis of weak gravitational lensing and galaxy clustering (3×2pt) in harmonic space with LSST-DESC analysis pipelines applied to Hyper Suprime-Cam Year 1 (HSC Y1) data. The HSC Y1 dataset, with imaging depth and galaxy number density similar to those expected for the first year of LSST observations, is an ideal testbed for validating DESC measurement and inference tools. We measure the full set of angular power spectra - cosmic shear, galaxy clustering, and galaxy-galaxy lensing - perform null tests, and correct for the impact of observing conditions on both the galaxy density and shear fields via mode deprojection. We validate our likelihood pipeline by reproducing the official HSC Y1 cosmic shear cosmological constraints with the DESC inference code. Jointly analysing all three two-point functions, we constrain ΛCDM and wCDM cosmologies, reporting results for cosmic shear, the combination of galaxy clustering and galaxy-galaxy lensing (2×2pt), and the full 3×2pt. From the joint 3×2pt ΛCDM analysis we find Ω_m = 0.249^+0.061_−0.051, σ₈ = 0.904^+0.098_−0.091, and S₈ ≡ σ₈√(Ω_m/0.3) = 0.821^+0.018_−0.021. This analysis validates the complete DESC 3x2pt infrastructure on survey data, providing the foundation for the forthcoming LSST Year 1 cosmological analysis.

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BibTeX RIS

BibTeX

@misc{sanchezcid2026lsstdesc,
  title = {{An LSST-DESC Precursor Project: Hyper Suprime-Cam Year 1 $3\times2$pt in Harmonic Space}},
  author = {D. Sanchez-Cid and J. Sanchez and I. Sevilla-Noarbe and D. Alonso and F. Andrade-Oliveira and H. Awan and C. Chang and J. Ellison and C. García-García and M. Ishak and E. Longley-Phillips and R. Mandelbaum and A. Nicola and E. Pedersen and J. Prat and E. Rykoff and E. Sanchez and N. Šarčević and M. Soares-Santos and M. Yamamoto and J. Zuntz and the LSST Dark Energy Science Collaboration},
  howpublished = {arXiv},
  year = {2026},
  month = oct,
  doi = {10.48550/arxiv.2609.39603},
  eprint = {2609.39603},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2609.39603},
  note = {CC BY 4.0},
}

RIS

TY  - UNPB
TI  - An LSST-DESC Precursor Project: Hyper Suprime-Cam Year 1 3×2pt in Harmonic Space
AU  - D. Sanchez-Cid
AU  - J. Sanchez
AU  - I. Sevilla-Noarbe
AU  - D. Alonso
AU  - F. Andrade-Oliveira
AU  - H. Awan
AU  - C. Chang
AU  - J. Ellison
AU  - C. García-García
AU  - M. Ishak
AU  - E. Longley-Phillips
AU  - R. Mandelbaum
AU  - A. Nicola
AU  - E. Pedersen
AU  - J. Prat
AU  - E. Rykoff
AU  - E. Sanchez
AU  - N. Šarčević
AU  - M. Soares-Santos
AU  - M. Yamamoto
AU  - J. Zuntz
AU  - the LSST Dark Energy Science Collaboration
PY  - 2026
DA  - 2026/10/09
PB  - arXiv
DO  - 10.48550/arxiv.2609.39603
UR  - https://arxiv.org/abs/2609.39603
AB  - We present the first fully photometric joint analysis of weak gravitational lensing and galaxy clustering (3×2pt) in harmonic space with LSST-DESC analysis pipelines applied to Hyper Suprime-Cam Year 1 (HSC Y1) data. The HSC Y1 dataset, with imaging depth and galaxy number density similar to those expected for the first year of LSST observations, is an ideal testbed for validating DESC measurement and inference tools. We measure the full set of angular power spectra - cosmic shear, galaxy clustering, and galaxy-galaxy lensing - perform null tests, and correct for the impact of observing conditions on both the galaxy density and shear fields via mode deprojection. We validate our likelihood pipeline by reproducing the official HSC Y1 cosmic shear cosmological constraints with the DESC inference code. Jointly analysing all three two-point functions, we constrain ΛCDM and wCDM cosmologies, reporting results for cosmic shear, the combination of galaxy clustering and galaxy-galaxy lensing (2×2pt), and the full 3×2pt. From the joint 3×2pt ΛCDM analysis we find Ω_m = 0.249^+0.061_−0.051, σ_8 = 0.904^+0.098_−0.091, and S_8 ≡ σ_8√(Ω_m/0.3) = 0.821^+0.018_−0.021. This analysis validates the complete DESC 3x2pt infrastructure on survey data, providing the foundation for the forthcoming LSST Year 1 cosmological analysis.
ER  -

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