CMB lensing imprints of cosmic voids in DESI Legacy Survey DR9 LRGs with photometric redshift calibration
Pith reviewed 2026-05-20 02:26 UTC · model grok-4.3
The pith
CMB lensing signals from DESI cosmic voids match Lambda CDM predictions with amplitude 1.016 plus or minus 0.054.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
By categorizing voids according to gravitational potential and stacking the Planck 2018 lensing convergence map on voids found in the DESI DR9 LRG catalog, the authors obtain two independent detections at roughly 17 sigma each. They compare the observed stacked signal to templates from Buzzard mocks that have been calibrated to match the sparseness and photometric redshift error distribution of the real data. The resulting amplitude parameter A_kappa equals 1.016 plus or minus 0.054 for the full sample and remains consistent with one across all populations and redshift bins from 0.35 to 0.95.
What carries the argument
The central mechanism is the potential-based separation of void-in-void and void-in-cloud populations combined with the stacking of the CMB lensing convergence map against mocks calibrated to observed photometric redshift errors and sample density.
If this is right
- The lensing-is-low tension disappears once mock catalogs are matched to the actual redshift error and density properties of the survey.
- Separate analysis of the two void populations produces two independent high-significance detections of the lensing imprint.
- The amplitude remains consistent with unity in every redshift bin from 0.35 to 0.95, supporting the standard model across this range.
Where Pith is reading between the lines
- The calibration method shown here could be applied to other large-scale structure tracers to test whether similar tensions arise from photometric redshift mismatches.
- If the same approach holds in future data releases with improved redshift precision, void lensing may provide independent constraints on the growth of structure.
- Extending the void selection to higher redshifts could reveal whether the current agreement persists or begins to deviate at earlier cosmic times.
Load-bearing premise
The Buzzard mocks, once calibrated with over one million DESI spectra, accurately reproduce the sparseness and photometric redshift error distributions of the observed LRG sample without biasing the stacked lensing signal.
What would settle it
A re-measurement of the stacked lensing amplitude using spectroscopic redshifts instead of photometric ones that yields a value for A_kappa significantly different from one would challenge the claimed agreement.
read the original abstract
The lensing imprint of cosmic voids in the Cosmic Microwave Background (CMB) provides a powerful test of the $\Lambda$CDM model. However, recent studies report a "lensing-is-low" tension between observations and mock predictions. To investigate this, we measure the stacked CMB lensing signal of 3D cosmic voids identified in the DESI Legacy Survey DR9 Luminous Red Galaxy (LRG) sample, cross-correlated with the Planck 2018 lensing map. We compare our observations to $\Lambda$CDM templates derived from Buzzard mocks, critically calibrated using over one million DESI spectra to perfectly match the sparseness and photometric redshift error distributions of the observed data. By categorizing voids based on their gravitational potential, we disentangle the signals of void-in-voids and void-in-clouds, achieving two independent record detection significances of $\sim 17\sigma$. We find full agreement between observations and simulated $\Lambda$CDM templates across all void populations and redshift bins ($0.35\! <\! z\! <\! 0.95$), measuring an amplitude parameter $A_\kappa = 1.016 \pm 0.054$ for the full sample. This highlights the necessity of accurate systematic control, effectively resolving the reported lensing tension within this dataset. This proceeding summarizes the results presented in Sartori et al. (2025).
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The manuscript measures the stacked CMB lensing convergence signal of 3D cosmic voids identified in the DESI Legacy Survey DR9 LRG sample (0.35 < z < 0.95) and cross-correlates it with the Planck 2018 lensing map. Voids are classified into void-in-void and void-in-cloud populations according to gravitational potential. Observed signals are compared against ΛCDM templates generated from Buzzard mocks that have been calibrated to match the observed galaxy sparseness and photometric redshift error distributions using >1 million DESI spectra. The analysis reports two independent ~17σ detections and an amplitude A_κ = 1.016 ± 0.054 for the full sample, claiming consistency with unity and resolution of the reported lensing-is-low tension.
Significance. If the mock calibration is shown to be sufficient, the work supplies a high-precision test of ΛCDM using void lensing with record detection significances and demonstrates that careful control of photometric systematics can eliminate apparent tensions. The separation of void populations by potential depth adds physical insight beyond a single stacked measurement.
major comments (2)
- The central claim that A_κ is consistent with unity and that the lensing tension is resolved rests on the fidelity of the calibrated Buzzard mocks. Matching only the marginal distributions of sparseness and photo-z errors does not automatically guarantee that the 3D void finder produces identical populations (in radius, depth, or void-in-void vs. void-in-cloud classification) or that line-of-sight projection and lensing-kernel weighting remain unbiased. Residual correlations between photo-z scatter and local density could shift the stacked κ profile even when the quoted error distributions appear matched. Additional validation comparing void statistics and lensing profiles between mocks and data is required before the amplitude measurement can be considered robust.
- Details on error propagation, covariance estimation, and the precise impact of data cuts on the lensing measurement are not fully specified. These elements directly affect the quoted uncertainty on A_κ and the claimed detection significances of ~17σ.
minor comments (1)
- As this is a proceedings summary of Sartori et al. (2025), some technical details are necessarily abbreviated; the main text would benefit from a concise table or figure showing the void radius and depth distributions in data versus calibrated mocks.
Simulated Author's Rebuttal
We thank the referee for their careful and constructive review of our manuscript. We value the recognition of the work's potential significance and have addressed each major comment below with specific plans for revision.
read point-by-point responses
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Referee: The central claim that A_κ is consistent with unity and that the lensing tension is resolved rests on the fidelity of the calibrated Buzzard mocks. Matching only the marginal distributions of sparseness and photo-z errors does not automatically guarantee that the 3D void finder produces identical populations (in radius, depth, or void-in-void vs. void-in-cloud classification) or that line-of-sight projection and lensing-kernel weighting remain unbiased. Residual correlations between photo-z scatter and local density could shift the stacked κ profile even when the quoted error distributions appear matched. Additional validation comparing void statistics and lensing profiles between mocks and data is required before the amplitude measurement can be considered robust.
Authors: We agree that demonstrating the sufficiency of the mock calibration is critical to supporting our central claims. The manuscript details the use of >1 million DESI spectra to calibrate the Buzzard mocks to match the observed sparseness and photometric redshift error distributions, which are the dominant systematics for photometric void identification. To strengthen this, we will add a new subsection with explicit comparisons of void population statistics (radius, depth, and void-in-void vs. void-in-cloud fractions) between data and calibrated mocks, as well as a direct comparison of the stacked lensing profiles. These additions will quantify any residual differences and confirm that the templates remain unbiased for the amplitude measurement. revision: yes
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Referee: Details on error propagation, covariance estimation, and the precise impact of data cuts on the lensing measurement are not fully specified. These elements directly affect the quoted uncertainty on A_κ and the claimed detection significances of ~17σ.
Authors: We acknowledge that, as a concise proceedings summary, the current text does not fully elaborate on all statistical procedures. We will revise the methods and results sections to provide complete details on error propagation, the covariance estimation approach (using the calibrated mocks to capture relevant variances), and quantitative tests of how data cuts influence the measured A_κ and detection significances. This will include explicit statements on how the ~17σ values are computed. revision: yes
Circularity Check
Mock calibration to observed sparseness and photo-z introduces moderate circularity in ΛCDM template comparison
specific steps
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fitted input called prediction
[Abstract]
"we compare our observations to ΛCDM templates derived from Buzzard mocks, critically calibrated using over one million DESI spectra to perfectly match the sparseness and photometric redshift error distributions of the observed data. ... measuring an amplitude parameter A_κ = 1.016 ± 0.054 for the full sample."
The ΛCDM templates used for comparison are derived from mocks calibrated to match the observed data's sparseness and photo-z errors. The amplitude A_κ is then measured by scaling these templates to the observed stacked lensing signal, so the reported agreement incorporates properties fitted from the same dataset rather than providing a fully independent prediction.
full rationale
The central result (A_κ = 1.016 ± 0.054, full agreement with ΛCDM) relies on templates generated from Buzzard mocks that were calibrated directly to the same DESI LRG dataset's sparseness and photometric redshift error distributions. While the Planck lensing map is external and the calibration targets only marginal distributions rather than the lensing signal itself, this still incorporates fitted properties of the measurement sample into the 'prediction', creating moderate circularity burden without fully reducing the claim to tautology by construction. No self-citation chains or self-definitional steps were identified in the provided text.
Axiom & Free-Parameter Ledger
free parameters (1)
- A_κ
axioms (1)
- domain assumption Buzzard mocks after calibration with DESI spectra match the sparseness and photometric redshift error distributions of the LRG sample.
Lean theorems connected to this paper
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IndisputableMonolith/Foundation/RealityFromDistinction.leanreality_from_one_distinction unclear?
unclearRelation between the paper passage and the cited Recognition theorem.
We identify our cosmic void sample using the LRG population... calibrated using over one million DESI spectra to perfectly match the sparseness and photometric redshift error distributions
What do these tags mean?
- matches
- The paper's claim is directly supported by a theorem in the formal canon.
- supports
- The theorem supports part of the paper's argument, but the paper may add assumptions or extra steps.
- extends
- The paper goes beyond the formal theorem; the theorem is a base layer rather than the whole result.
- uses
- The paper appears to rely on the theorem as machinery.
- contradicts
- The paper's claim conflicts with a theorem or certificate in the canon.
- unclear
- Pith found a possible connection, but the passage is too broad, indirect, or ambiguous to say the theorem truly supports the claim.
Reference graph
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discussion (0)
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