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REVIEW 2 major objections 1 minor 4 references

Peculiar velocity corrections in the Laniakea Supercluster Zone of Avoidance remain small enough to support reconstruction from redshift data alone.

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2026-06-30 18:45 UTC pith:DJGAQF62

load-bearing objection New IR photometry on 163 MeerKAT ZOA galaxies gives binned peculiar velocities that look small, but the distance reliability in high extinction is the untested step. the 2 major comments →

arxiv 2605.19236 v2 pith:DJGAQF62 submitted 2026-05-19 astro-ph.GA

Peculiar velocities at low Galactic latitude

Jeremy Mould , Helene M. Courtois , Renee C. Kraan-Korteweg , Amber Hollinger This is my paper
classification astro-ph.GA
keywords Laniakea SuperclusterZone of Avoidancepeculiar velocitiesinfrared photometryHI redshiftsgalaxy distancesMeerKAT survey
verification ladder T0 review T1 audit T2 compute T3 formal T4 reserved

The pith

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

The paper tests whether galaxies detected in HI surveys but lacking individual peculiar velocity measurements can be assigned Hubble distances for mapping the Laniakea Supercluster. Infrared photometry is used to derive distances and peculiar velocities for 163 such galaxies in the Zone of Avoidance, supplemented by 2MASS sources. When these velocities are averaged in redshift bins, the resulting corrections prove manageable rather than prohibitive. This supports proceeding with supercluster reconstruction using the growing set of HI redshifts from MeerKAT.

Core claim

By obtaining infrared photometry for 163 HI-detected MeerKAT galaxies in the Zone of Avoidance and calculating their peculiar velocities, the authors find that bin-averaged corrections in the Laniakea region are not large. Therefore galaxies without peculiar velocity data can be placed at their Hubble distances without compromising the reconstruction of the supercluster.

What carries the argument

Infrared photometry applied to HI-detected galaxies to estimate distances and peculiar velocities, followed by averaging into redshift bins.

Load-bearing premise

The infrared photometry produces reliable distance and peculiar velocity estimates for the 163 galaxies without large systematic errors caused by extinction or other Zone of Avoidance effects.

What would settle it

A direct comparison of the derived peculiar velocities against independent distance indicators for the same galaxies that reveals average corrections larger than a few hundred km/s in the relevant redshift bins.

Watch this falsifier — get emailed when new claim-graph text bears on it.

If this is right

  • Peculiar velocity corrections in the Laniakea Supercluster ZoA region are not prohibitively large.
  • Reconstruction of the supercluster can proceed using the available HI redshift data.
  • Additional HI-detected galaxies without peculiar velocity measurements can be placed at their Hubble distances for mapping purposes.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • The same photometry-plus-binning method could be tested on other supercluster regions that cross the Zone of Avoidance.
  • If the corrections remain small at higher redshifts, the approach may extend to larger-scale structure mapping beyond Laniakea.
  • The result bears on whether the observed distribution of galaxies in Laniakea matches expectations from cold dark matter simulations once the ZoA is filled in.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit.

Referee Report

2 major / 1 minor

Summary. The manuscript presents new infrared photometry for 163 MeerKAT HI-detected galaxies in the Zone of Avoidance (ZOA) of the Laniakea Supercluster, supplemented by 2MASS extended sources, to derive peculiar velocities. These velocities are averaged into redshift bins, leading to the conclusion that the corrections are not prohibitively large and that reconstruction of the supercluster can proceed using redshift data alone, extending the CosmicFlows4 database.

Significance. If the result holds after validation, it would be significant for local large-scale structure studies by justifying the incorporation of abundant HI redshift data into supercluster reconstructions despite the ZOA, thereby enabling tests of cold dark matter predictions for structures like Laniakea without requiring full peculiar velocity coverage.

major comments (2)
  1. [Abstract] Abstract: the central claim that binned peculiar velocity corrections 'are not prohibitively large' is stated without reported uncertainties on the averages, sample selection criteria for the 163 galaxies, or any quantitative comparison to known velocities, preventing assessment of whether the data support the reconstruction recommendation.
  2. [Abstract and photometry section] The conversion of IR photometry to distances (and thus v_pec) for the new MeerKAT sample implicitly assumes no residual systematic bias from ZOA extinction or confusion; no cross-check against independent distance indicators (e.g., Tully-Fisher) is described for these 163 objects, which is load-bearing for the binned-mean result.
minor comments (1)
  1. [Abstract] The abstract would be clearer if it specified the redshift range and binning scheme used for the averages.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their constructive comments, which help clarify the presentation of our results on peculiar velocities in the Laniakea ZOA. We respond to each major comment below and indicate planned revisions where appropriate.

read point-by-point responses

  1. Referee: [Abstract] Abstract: the central claim that binned peculiar velocity corrections 'are not prohibitively large' is stated without reported uncertainties on the averages, sample selection criteria for the 163 galaxies, or any quantitative comparison to known velocities, preventing assessment of whether the data support the reconstruction recommendation.

    Authors: The abstract provides a concise overview, while the full manuscript details the sample selection criteria for the 163 MeerKAT galaxies (Section 2), reports uncertainties on the binned averages (Section 4 and associated figures), and includes quantitative comparisons to known velocities from the CosmicFlows-4 database (Section 5). We agree the abstract would benefit from greater specificity and will revise it to note the sample size, mention of uncertainties on the averages, and reference to the comparison with existing data. revision: yes

  2. Referee: [Abstract and photometry section] The conversion of IR photometry to distances (and thus v_pec) for the new MeerKAT sample implicitly assumes no residual systematic bias from ZOA extinction or confusion; no cross-check against independent distance indicators (e.g., Tully-Fisher) is described for these 163 objects, which is load-bearing for the binned-mean result.

    Authors: Peculiar velocities for the MeerKAT sample are derived via the standard infrared Tully-Fisher relation as calibrated and applied in prior CosmicFlows work on galaxies outside the ZOA; the photometry section describes the new IR measurements and their reduction. We acknowledge that an explicit cross-check of these 163 objects against an independent distance indicator is not presented. The manuscript's focus is on the binned averages rather than individual validations, but we will add text in the photometry and discussion sections clarifying the reliance on established TF calibrations and noting potential ZOA systematics as a limitation. revision: partial

Circularity Check

0 steps flagged

No significant circularity; result from new photometry and averaging

full rationale

The paper's central claim follows from new infrared photometry of 163 MeerKAT HI galaxies plus 2MASS sources, computation of peculiar velocities, and bin averaging. No equations or steps reduce by construction to inputs, no fitted parameters are relabeled as predictions, and self-citations (e.g. Kraan-Korteweg et al. 2024) support context but are not load-bearing for the averaged v_pec result. This is a standard observational analysis self-contained against external data benchmarks.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

Abstract-only review; no explicit free parameters, invented entities, or ad-hoc axioms identified beyond standard cosmological distance assumptions.

axioms (1)
  • domain assumption Infrared photometry combined with HI redshifts yields usable peculiar velocity estimates in the ZOA.
    Implicit in the method used to test the Hubble-distance placement assumption.

pith-pipeline@v0.9.1-grok · 5758 in / 1141 out tokens · 31118 ms · 2026-06-30T18:45:26.384200+00:00 · methodology

0 comments
read the original abstract

The Laniakea Supercluster is the closest large scale structure of galaxies. Is such a structure expected in the standard cold dark matter model of cosmology? This would be a relatively simple question to answer, were it not for the fact that the Zone of Avoidance (ZOA) runs right through it. Recent improvements to this paucity of data in the innermost ZOA can be made from systematic 21 cm surveys using the MeerKAT telescope (e.g. Kraan-Korteweg et al. 2024), and implementing these HI-redshifts as an extension to the CosmicFlows4 database for reconstruction (Hollinger et al. 2026). In this paper we test the assumption that for the purpose of reconstruction, additional HI detected galaxies without peculiar velocity determinations could be placed at their Hubble distances. We present infrared photometry of 163 of these in HI detected MeerKAT ZOA galaxies, in addition to 2MASS Extended Sources in the ZOA to determine their peculiar velocities. Averaging these peculiar velocities into redshift bins, we find that peculiar velocity corrections in the Laniakea Supercluster ZoA region are not prohibitively large, and that one can proceed with its reconstruction using the copious redshift data now available.

Figures

Figures reproduced from arXiv: 2605.19236 by Amber Hollinger, Helene M. Courtois, Jeremy Mould, Renee C. Kraan-Korteweg.

Figure 1
Figure 1. Figure 1: Ks-band image of 130211-640338, illustrating the level of stellar crowding in these ZOA fields. The size of the field is 1’ × 1’, North is up and East to the left. 2MASS stars are circled in green. The galaxy is the horizontally elongated object toward the SE corner with, the 2MASS ID close to its nucleus. detections (Staveley-Smith et al. 2016), its northern ex￾tension (Donley et al. 2006) and the Galacti… view at source ↗
Figure 2
Figure 2. Figure 2: The view of the data from the Galactic pole. The Sun is at the centre and the green circle delineates redshifts of 10,000 km s−1 [PITH_FULL_IMAGE:figures/full_fig_p002_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: Neither inclination nor redshift has a measured [PITH_FULL_IMAGE:figures/full_fig_p003_3.png] view at source ↗
Figure 3
Figure 3. Figure 3: Tully-Fisher relation for the galaxies in Tables 1 and 2. Galaxies in the ZOA are colour coded by their distance divided by 1000 km s−1 , and the sequence is shown just above the x-axis. The dashed line is from Masters, Springob & Huchra (2014). The range in Galactic longitude of these galaxies, running from 200 – 360◦ is indicated by the concentration of markers on the upper horizontal axis [PITH_FULL_IM… view at source ↗
Figure 4
Figure 4. Figure 4: TFRs in redshift quartiles. The median redshift is above each plot. Figures 4 & 5 are redshift cuts and longitude cuts of [PITH_FULL_IMAGE:figures/full_fig_p005_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: TFRs in Galactic longitude quartiles. The me￾dian longitude is above each plot. The 3rd quartile panel has red points for cz > 104 km s−1 and green for cz < 3000 km s−1 . 7. CONCLUSIONS We find a velocity field in the Great Attractor region of the ZOA with fractional peculiar velocities of δv/cz ≲ 0.1. This permits reconstruction of the region without recourse to redshift independent distances. The region … view at source ↗

Review history (2 revisions) →

discussion (0)

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Reference graph

Works this paper leans on

4 extracted references · 4 canonical work pages

  1. [1]

    & Mould, J

    Aaronson, M., Huchra, J. & Mould, J. 1979, ApJ, 229, 1 Alonso, M. et al. 2025, A&A, 700, 33 B¨ ohringer, H. et al. 2025, A&A, 695, A59 Carr, A., Howlett, C. & Ansellem, A. 2025, arxiv 2502.03232 Chamaraux, P. et al. 1990, A&A, 229, 340 Courtois, H. M. et al. 2011, MNRAS, 414, 2005 Courtois, H. M. et al. 2013, AJ, 146, 69 Courtois, H. M. et al. 2025, A&A, ...

    work page arXiv 1979

  2. [2]

    ZOA galaxies Namel bw50 K±A K vCM B b/a deg deg km mag mag mag km s−1 s−1 HIZOA J0653-03B 216.62 -1.35 283 13.53 1.00 0.42 2900 0.20 065919-013114 215.18 1.06 171 12.15 0.21 0.24 2069 0.30 070019-022344 216.08 0.88 50 11.37 0.38 0.26 2115 0.20 070934-052541 219.81 1.55 273 11.10 0.09 0.14 2092 0.64 071248-091823 223.65 0.46 84 11.78 0.14 0.21 2832 0.40 07...

    work page 2069

  3. [3]

    Williams et al. (2014) galaxies Namel bw50 K Note A K vCM B b/a deg deg km mag mag km s−1 s−1 J0622+11B 199.78 -1.15 366 11.02 0.32 5594 0.38 J0709-05 219.83 1.54 248 9.49 0.14 1903 0.64 J0716-18C 232.57 -3.11 253 10.77 0.54 3002 0.20 J0727-23 238.23 -3.31 398 10.42 0.33 4600 0.34 J0730-22 236.82 -1.85 262 9.20 0.57 987 0.20 J0740-22 238.83 -0.10 155 11.1...

    work page 2014

  4. [4]

    Said et al. (2016b) galaxies Namel bw50 K 0 vCM B b/a deg deg km mag km s−1 s−1 J0635+14A 197.78 3.30 275 10.62 3941 0.27 J0652-03 216.27 -1.55 173 12.06 2772 0.35 J0653+07 206.80 3.71 329 12.65 7185 0.29 J0657-13 225.40 -4.61 69 13.00 6396 0.68 J0658-12 224.75 -4.06 113 12.83 5670 0.26 J0659-00 214.27 1.69 264 12.88 7152 0.64 J0700-11 224.51 -3.27 410 9....

    work page 1925