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PreprintCC BY 4.0arXiv

The Redshift-Space Cluster-Galaxy Cross-Correlation as a Probe of Gravity on Cosmic Scales

  • Nicole Marcelina Gountanis
  • David H. Weinberg
  • Andrés N. Salcedo
  • Claire Lamman
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Abstract

Testing General Relativity (GR) on cosmological scales requires probes that are directly sensitive to gravitational dynamics. We present a Fisher matrix forecast of how well the Dark Energy Spectroscopic Instrument (DESI) Bright Galaxy Survey (BGS) can constrain departures from GR through the cluster infall velocity field, using the redshift-space cluster-galaxy cross-correlation function ξscg(rp, rπ) as the primary observable. We construct mock catalogs from the AbacusSummit N-body simulations, using a Halo Occupation Distribution (HOD) model for galaxies and a log-normal mass-observable relation for cluster selection. We parameterize departures from GR with a single multiplicative factor FG that rescales halo infall velocities relative to the GR prediction. Marginalizing over the HOD, mass-observable, and cosmological parameters, we find that DESI BGS can constrain FG to σ(FG) = 0.033 at z ∼ 0.3. This precision is sufficient to distinguish representative f(R) and Galileon gravity models from GR at ≳ 4σ. The strongest limitation is a degeneracy between FG and the scatter in the cluster mass-observable relation, while the constraint shows no strong degeneracy with any individual HOD parameter. Perfect knowledge of the galaxy-halo connection would improve the constraint to σ(FG) ≈ 0.015, and including the galaxy autocorrelation function in the data vector could recover part of this improvement. The same data vector yields tight constraints on the cosmological parameters, σ(Ωm) = 0.010 and σ(σ8) = 0.010, only moderately correlated with FG. These results demonstrate the potential of DESI BGS cluster-galaxy correlations to test gravity on quasi-linear scales, complementary to existing modified gravity probes and to weak-lensing cluster mass profiles.

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Cite

BibTeXRIS
BibTeX
@misc{gountanis2026redshiftspace,
  title = {{The Redshift-Space Cluster-Galaxy Cross-Correlation as a Probe of Gravity on Cosmic Scales}},
  author = {Nicole Marcelina Gountanis and David H. Weinberg and Andrés N. Salcedo and Claire Lamman},
  howpublished = {arXiv},
  year = {2026},
  month = oct,
  doi = {10.48550/arxiv.2610.37782},
  eprint = {2610.37782},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2610.37782},
  note = {CC BY 4.0},
}
RIS
TY  - UNPB
TI  - The Redshift-Space Cluster-Galaxy Cross-Correlation as a Probe of Gravity on Cosmic Scales
AU  - Nicole Marcelina Gountanis
AU  - David H. Weinberg
AU  - Andrés N. Salcedo
AU  - Claire Lamman
PY  - 2026
DA  - 2026/10/27
PB  - arXiv
DO  - 10.48550/arxiv.2610.37782
UR  - https://arxiv.org/abs/2610.37782
AB  - Testing General Relativity (GR) on cosmological scales requires probes that are directly sensitive to gravitational dynamics. We present a Fisher matrix forecast of how well the Dark Energy Spectroscopic Instrument (DESI) Bright Galaxy Survey (BGS) can constrain departures from GR through the cluster infall velocity field, using the redshift-space cluster-galaxy cross-correlation function ξ^s_cg(r_p, r_π) as the primary observable. We construct mock catalogs from the AbacusSummit N-body simulations, using a Halo Occupation Distribution (HOD) model for galaxies and a log-normal mass-observable relation for cluster selection. We parameterize departures from GR with a single multiplicative factor F_G that rescales halo infall velocities relative to the GR prediction. Marginalizing over the HOD, mass-observable, and cosmological parameters, we find that DESI BGS can constrain F_G to σ(F_G) = 0.033 at z ∼ 0.3. This precision is sufficient to distinguish representative f(R) and Galileon gravity models from GR at ≳ 4σ. The strongest limitation is a degeneracy between F_G and the scatter in the cluster mass-observable relation, while the constraint shows no strong degeneracy with any individual HOD parameter. Perfect knowledge of the galaxy-halo connection would improve the constraint to σ(F_G) ≈ 0.015, and including the galaxy autocorrelation function in the data vector could recover part of this improvement. The same data vector yields tight constraints on the cosmological parameters, σ(Ω_m) = 0.010 and σ(σ_8) = 0.010, only moderately correlated with F_G. These results demonstrate the potential of DESI BGS cluster-galaxy correlations to test gravity on quasi-linear scales, complementary to existing modified gravity probes and to weak-lensing cluster mass profiles.
ER  -