arxiv: 2604.11694 · v1 · submitted 2026-04-13 · 🌌 astro-ph.CO

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Cosmological inference with halo clustering reconstructed from the redshift-space galaxy distribution

Ryuichiro Hada, Teppei Okumura

Authors on Pith no claims yet

Pith reviewed 2026-05-10 15:03 UTC · model grok-4.3

classification 🌌 astro-ph.CO

keywords halo reconstructionredshift-space distortionseffective field theorycosmological parametersgrowth rate fσ8galaxy clusteringAlcock-Paczynski parameters

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The pith

Reconstructing halo centers from redshift-space galaxies yields unbiased cosmological parameters with over 20 percent tighter errors on the growth rate.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper tests halo reconstruction via the cylinder grouping method as a way to improve full-shape analyses of redshift-space distortions. Using DESI-like luminous red galaxy mocks, the authors apply effective field theory modeling to the power spectrum of the reconstructed sample and show that the main reconstruction effects are absorbed into existing model components. This produces stable constraints on parameters such as fσ8 even when smaller scales are included, while cutting the uncertainty by more than 20 percent relative to direct galaxy clustering. A reader would care because the approach extracts more information from the same data without adding new parameters or losing robustness.

Core claim

The reconstructed-halo sample yields unbiased constraints on cosmological parameters, including the growth rate fσ8 and Alcock-Paczynski parameters. Compared to the galaxy sample, it enables both improved robustness and increased statistical precision: the inferred fσ8 remains stable when extending the fit beyond k_max ≃ 0.2 h Mpc^{-1}, with its uncertainty reduced by more than 20 percent. The dominant reconstruction-induced systematics are captured by a multipole-dependent rescaling on large scales, while residual small-scale changes are absorbed by the standard counterterm and stochastic sectors without new parameters.

What carries the argument

The cylinder grouping reconstruction, which selects an effective halo center tracer from the observed galaxy distribution to reduce satellite and Finger-of-God contributions before power-spectrum modeling.

Load-bearing premise

The dominant reconstruction-induced systematics are fully captured by a multipole-dependent rescaling inferred from large-scale data and any residual small-scale changes are completely absorbed by the standard EFT counterterm and stochastic sectors without introducing bias.

What would settle it

A significant bias appearing in the recovered fσ8 when the reconstructed-halo fit is extended past k_max = 0.2 h Mpc^{-1}, or the uncertainty on fσ8 failing to shrink by at least 20 percent relative to the galaxy sample in the same mocks.

Figures

Figures reproduced from arXiv: 2604.11694 by Ryuichiro Hada, Teppei Okumura.

**Figure 2.** Figure 2: FIG. 2: Cosmological constraints in the compressed pa [PITH_FULL_IMAGE:figures/full_fig_p011_2.png] view at source ↗

**Figure 4.** Figure 4: FIG. 4: Constraints on the growth-rate parameter [PITH_FULL_IMAGE:figures/full_fig_p012_4.png] view at source ↗

**Figure 5.** Figure 5: FIG. 5: Full posterior distributions in the complete parameter space for galaxies (red), halos (blue), and reconstructed halos [PITH_FULL_IMAGE:figures/full_fig_p014_5.png] view at source ↗

**Figure 6.** Figure 6: FIG. 6: Same as Fig. 4, but for the AP parameters [PITH_FULL_IMAGE:figures/full_fig_p015_6.png] view at source ↗

read the original abstract

Accurate modeling of small-scale redshift-space clustering is crucial for full shape RSD analyses, where satellite galaxies contribute to 1-halo terms and Finger-of-God distortions. We investigate halo reconstruction based on the cylinder grouping (CG) method of Okumura et al. (2017), which selects an effective halo center tracer from the observed galaxy distribution, and how it impacts cosmological parameter inference. Using DESI-like luminous red galaxy mock catalogs from the AbacusSummit simulations at $z=1.1$, we perform effective field theory (EFT)-based full-shape modeling of the power spectrum of the reconstructed-halo sample. We show that the dominant reconstruction-induced systematics can be described and incorporated within the standard EFT framework. In particular, a simple multipole-dependent rescaling inferred directly from the data on large scales captures the dominant effect, while residual small-scale changes are absorbed by the standard counterterm and stochastic sector, without introducing additional reconstruction-specific parameters. The reconstructed-halo sample yields unbiased constraints on cosmological parameters, including the growth rate $f\sigma_8$ and Alcock-Paczynski parameters. Compared to the galaxy sample, it enables both improved robustness and increased statistical precision: the inferred $f\sigma_8$ remains stable when extending the fit beyond $k_{\max}\simeq 0.2\,h\,{\rm Mpc}^{-1}$, with its uncertainty reduced by more than $20\%$.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Desk Editor's Note private letter to a colleague

Reconstruction plus a fixed multipole rescaling lets EFT fits stay unbiased to higher k on mocks and cuts fσ8 error by >20%.

read the letter

The main point is that applying the 2017 cylinder-grouping reconstruction to DESI-like LRG mocks lets you push standard EFT full-shape fits past k_max ~0.2 h/Mpc without bias or extra parameters, and the fσ8 uncertainty drops by more than 20 percent while AP parameters stay stable. They infer a simple multipole-dependent rescaling from large-scale data, fix it, and let the usual counterterms and stochastic terms absorb the remaining small-scale shifts from reconstruction. On the AbacusSummit mocks at z=1.1 the recovered cosmology, including growth rate, looks unbiased in their tests. That is the concrete result worth noting. It is a useful practical extension rather than a new theoretical framework, but the quantified precision gain and the claim that no reconstruction-specific terms are needed are new in this context. The mock tests are clean and directly relevant to upcoming survey analyses. The soft spot is the fixed rescaling step. Because it is measured once from the same large-scale data and then held constant, any mismatch between that constant-per-multipole correction and the true scale dependence introduced by reconstruction (especially near the 1-halo regime) could in principle shift the posterior or narrow the errors. Their mocks do not show this, but the paper would be stronger with an explicit check of how results change if the rescaling is varied within its uncertainty or if different mock realizations are used. Real data will also bring extra observational systematics not present in the mocks. This work is for people running full-shape RSD analyses on DESI, Euclid, or similar samples who want to know whether reconstruction can safely extend the fitting range. It deserves peer review because the tests are concrete, the improvement is measured, and the central claim is falsifiable on the mocks they provide.

Referee Report

2 major / 2 minor

Summary. The paper examines halo reconstruction from redshift-space galaxy distributions using the cylinder grouping method on DESI-like LRG mocks from AbacusSummit at z=1.1. It applies EFT full-shape power spectrum modeling to the reconstructed-halo sample and shows that a multipole-dependent rescaling (inferred from large-scale data) plus standard counterterms and stochastic terms capture reconstruction systematics, yielding unbiased constraints on cosmological parameters including fσ8 and Alcock-Paczynski parameters, with improved robustness and >20% smaller uncertainty on fσ8 when extending fits beyond k_max ≃ 0.2 h Mpc^{-1}.

Significance. If the results hold, the approach provides a practical route to extend full-shape RSD analyses to smaller scales by mitigating 1-halo and FoG contributions without new free parameters, potentially increasing statistical power on growth-rate and AP measurements from surveys like DESI. The use of realistic mocks to demonstrate unbiased recovery and the parameter-free character of the rescaling (within the EFT framework) are explicit strengths.

major comments (2)

[§4] §4 (Results on mocks): the claim that fσ8 remains stable and its uncertainty drops by >20% when k_max is extended requires explicit comparison of posterior means, widths, and covariances between the galaxy and reconstructed-halo samples at both k_max=0.2 and higher; without tabulated values or figures showing the shift in best-fit fσ8 and the effective degrees of freedom, it is unclear whether the precision gain is robust to the choice of covariance estimation.
[§3.2] §3.2 (EFT modeling and rescaling): the multipole-dependent rescaling is inferred once from large-scale data and then held fixed; the manuscript should demonstrate (e.g., via mock ensemble tests) that any residual mismatch between this constant-per-multipole correction and the true scale-dependent reconstruction effect does not shift the posterior mean of fσ8 or AP parameters when the fit range is extended, since the rescaling is not marginalized.

minor comments (2)

[Abstract and §3] The abstract states the rescaling is 'inferred directly from the data on large scales'; the corresponding section should specify the exact k-range and multipoles used for this inference and whether the same data vector is later used for the cosmological fit.
[Figures and §4] Figure captions and text should clarify whether the reported error reduction on fσ8 is computed at fixed k_max or when the reconstructed sample allows a higher k_max; the two cases have different interpretations for robustness.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their positive assessment of our work and for the constructive comments, which have helped clarify the presentation of our results. We address each major comment point by point below and have revised the manuscript accordingly.

read point-by-point responses

Referee: [§4] §4 (Results on mocks): the claim that fσ8 remains stable and its uncertainty drops by >20% when k_max is extended requires explicit comparison of posterior means, widths, and covariances between the galaxy and reconstructed-halo samples at both k_max=0.2 and higher; without tabulated values or figures showing the shift in best-fit fσ8 and the effective degrees of freedom, it is unclear whether the precision gain is robust to the choice of covariance estimation.

Authors: We agree that a more explicit side-by-side comparison strengthens the claim. In the revised manuscript we have added Table 2, which tabulates the posterior means and 68% credible intervals for fσ8, α∥, and α⊥ (together with χ²/dof) for both the galaxy and reconstructed-halo samples at k_max = 0.20 h Mpc⁻¹ and k_max = 0.25 h Mpc⁻¹. We have also added Figure 8, which overlays the 1D marginalized posteriors and 2D contours for these parameters. All fits use the identical covariance matrix estimated from the full mock ensemble, so the comparison is internally consistent; the effective number of degrees of freedom is set by the EFT model and remains the same across the two k_max choices. The tabulated values confirm that the fσ8 mean shifts by less than 0.3σ while the uncertainty decreases by 22–25%, and the χ²/dof stays acceptable. revision: yes
Referee: [§3.2] §3.2 (EFT modeling and rescaling): the multipole-dependent rescaling is inferred once from large-scale data and then held fixed; the manuscript should demonstrate (e.g., via mock ensemble tests) that any residual mismatch between this constant-per-multipole correction and the true scale-dependent reconstruction effect does not shift the posterior mean of fσ8 or AP parameters when the fit range is extended, since the rescaling is not marginalized.

Authors: We have performed the requested ensemble test and now report the results in a new paragraph of §3.2 together with Appendix C. For each of the 25 mocks we (i) infer the three multipole rescaling factors from the k < 0.10 h Mpc⁻¹ range exactly as in the main analysis, (ii) apply those fixed factors to the full k-range up to 0.25 h Mpc⁻¹, and (iii) compare the resulting posterior means for fσ8, α∥, and α⊥ against the means obtained when the rescaling factors are allowed to vary freely (or are re-inferred over the full range). The mean bias in fσ8 across the ensemble remains < 0.2σ and is statistically indistinguishable from the bias obtained with the fixed rescaling; the same holds for the AP parameters. The additional freedom does not meaningfully tighten the constraints, confirming that the fixed, large-scale-derived rescaling introduces no detectable systematic shift once the standard counterterms and stochastic terms are included. revision: yes

Circularity Check

1 steps flagged

Minor self-citation to prior CG reconstruction method; central EFT-based inference and unbiased fσ8 claims remain independent

specific steps

self citation load bearing [Abstract]
"We investigate halo reconstruction based on the cylinder grouping (CG) method of Okumura et al. (2017), which selects an effective halo center tracer from the observed galaxy distribution"

The reconstruction procedure itself is introduced by citation to prior work sharing an author; while this is a normal methodological reference rather than a circular justification of the cosmological results, it is the only self-citation present and therefore registers as a minor instance under the scoring rubric.

full rationale

The paper defines its halo sample via the cylinder-grouping reconstruction of Okumura et al. (2017) and then fits an EFT power-spectrum model that includes a multipole-dependent rescaling fitted once on large-scale data. The reported unbiased cosmological constraints and >20% precision gain on fσ8 are obtained by comparing the posterior to the known input cosmology of the AbacusSummit mocks; neither the rescaling nor the final parameter values are defined in terms of themselves or forced by the self-citation. The self-citation supplies only the operational definition of the sample, not a load-bearing uniqueness theorem or ansatz that would make the inference results tautological.

Axiom & Free-Parameter Ledger

1 free parameters · 2 axioms · 0 invented entities

The central claim rests on the prior CG reconstruction method, standard EFT assumptions for galaxy power spectra, and the representativeness of AbacusSummit mocks; the multipole rescaling is data-driven rather than a new free parameter in the cosmological fit.

free parameters (1)

multipole-dependent rescaling
Inferred directly from large-scale data to capture dominant reconstruction effect; not introduced as a new cosmological fit parameter.

axioms (2)

domain assumption Standard EFT framework accurately models galaxy and halo power spectra including bias, counterterms, and stochastic terms
Invoked to absorb residual small-scale changes without additional reconstruction-specific parameters.
domain assumption AbacusSummit mocks at z=1.1 accurately represent DESI LRG sample properties
Used as the basis for all tests of unbiased constraints and precision.

pith-pipeline@v0.9.0 · 5558 in / 1559 out tokens · 74162 ms · 2026-05-10T15:03:53.694302+00:00 · methodology

discussion (0)

Reference graph

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