arxiv: 2604.11886 · v2 · submitted 2026-04-13 · 🌌 astro-ph.GA

The GMRT archive atomic gas survey -- IV. Consistency of the dark matter halo perturbation parameter from morphological and kinematic lopsidedness of galaxies

Prerana Biswas , Narendra Nath Patra , Veselina Kalinova This is my paper

Pith reviewed 2026-05-10 14:49 UTC · model grok-4.3

classification 🌌 astro-ph.GA

keywords galaxy lopsidednessdark matter halomorphological asymmetrykinematic asymmetryFourier analysisrotation curvesGMRT atomic gas survey

0 comments p. Extension

The pith

Assuming lopsidedness arises from a lopsided dark matter halo, morphological and kinematic halo perturbation parameters match in the same radial range.

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

This paper investigates the lopsidedness observed in many galaxies by comparing measures derived from the shapes of stellar and gas disks with those from their velocity fields. The authors assume this asymmetry arises from a lopsided dark matter halo and extract halo perturbation parameters in matching radial ranges using Fourier analysis for morphology and three-dimensional kinematic models for kinematics. They detect a linear correlation between the two parameters, though it lacks statistical significance in their sample of eleven galaxies. The work establishes a uniform framework for testing whether morphological and kinematic lopsidedness reflect the same underlying halo perturbation. This consistency, if confirmed, would link galaxy shapes directly to dark matter distributions without relying on rare events.

Core claim

Assuming lopsidedness originates due to a lopsided halo, the morphological and kinematic halo perturbation parameters are found in the same radial range. The detected linear correlation between them is not statistically significant for the small sample of eleven galaxies. This approach provides a more uniform and physically consistent framework to test the theoretically expected similarity between morphological and kinematic halo perturbation parameters. Further, the discrepancy between them does not appear to depend on the nature of the rotation-curve asymmetry of the two sides of the galaxy.

What carries the argument

Fourier decomposition of surface brightness and velocity fields to quantify lopsidedness, combined with 3D kinematic modeling of rotation curves to derive halo perturbation parameters.

If this is right

The method yields halo perturbation parameters from both morphological and kinematic data in identical radial ranges.
Discrepancies between the parameters show no dependence on rotation-curve asymmetry types.
Extending to larger samples can robustly assess the similarity of morphological and kinematic halo perturbations.
Moderate lopsidedness is interpreted as a response to the halo potential rather than isolated events.

Where Pith is reading between the lines

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

If confirmed with larger samples, this would indicate that dark matter halos commonly exhibit lopsidedness influencing galaxy disks.
Such a framework could be applied to test halo asymmetry predictions from cosmological simulations of galaxy formation.
Future observations might distinguish halo-driven lopsidedness from other causes like tidal interactions in specific galaxy types.

Load-bearing premise

Lopsidedness in galaxies originates primarily from a lopsided dark matter halo potential.

What would settle it

A larger sample of galaxies with similar Fourier and kinematic measurements showing no statistically significant correlation between morphological and kinematic halo perturbation parameters.

Figures

Figures reproduced from arXiv: 2604.11886 by Narendra Nath Patra, Prerana Biswas, Veselina Kalinova.

**Figure 1.** Figure 1: The radial distribution of the ratio of amplitudes of different Fourier modes to the 𝑚 = 0 mode found in the Fourier analysis of the stellar disk. The images of the respective galaxies for which the Fourier analysis is done are shown just below each plot of the radial distribution of different modes. Optical images for most galaxies, excluding NGC 7292 and NGC 7610, were taken from SPITZER IRAC-3.6𝜇m data,… view at source ↗

**Figure 2.** Figure 2: The radial distribution of the ratio of amplitudes of different Fourier modes to the 𝑚 = 0 mode found in the Fourier analysis of the H i disk. The images of the respective galaxies for which the Fourier analysis is done are shown just below each plot of the radial distribution of different modes. The concentric white ellipses over-plotted in the images of the H i disks, are centred at the optical centre of… view at source ↗

**Figure 3.** Figure 3: Distribution of the average of the ratio of the amplitudes for 𝑚 = 1, 2, 3 modes to 𝑚 = 0 mode in the inner and outer regions for both the stellar and gas disk. It is to be noted that the quantities marked as diamond for each galaxy are not an average ratio; these are the values of the ratios at the maximum radius of the H i disk. The morphologies of the galaxies are noted in the x-axis. For each mode, gal… view at source ↗

**Figure 4.** Figure 4: The rotation curve of the galaxies from the approaching side, the receding side and the whole galactic disk. MNRAS 000, 1–15 (2015) [PITH_FULL_IMAGE:figures/full_fig_p011_4.png] view at source ↗

**Figure 5.** Figure 5: Distribution of the average value of the lopsided halo perturbation parameter found from the morphological distortion of 𝑚 = 1 mode in the outer region of the stellar and gas disk. Galaxies are colour-coded to indicate if they are non-isolated or isolated. The morphologies of each galaxy are noted on the x-axis. previous sections [PITH_FULL_IMAGE:figures/full_fig_p012_5.png] view at source ↗

**Figure 6.** Figure 6: Comparison of 𝜖𝑘𝑖𝑛 and < 𝜖1 > measured between Rℎ,𝐻𝐼 and 2Rℎ,𝐻𝐼 for various types of differences in the rotation curves. The large data points are from our study, and the small data points are from the study van Eymeren et al. (2011b). The solid blue line and the blue shaded region respectively denote where 𝜖𝑘𝑖𝑛=< 𝜖1 > and scatter of represented data points from our study around this line. ther estimated t… view at source ↗

**Figure 7.** Figure 7: Comparison of 𝜖𝑘𝑖𝑛 and < 𝜖1 > measured between Rℎ,𝐻𝐼 and R𝑚𝑎𝑥,𝐻𝐼 for various types of differences in the rotation curves. The solid blue line and the blue shaded region respectively denote where 𝜖𝑘𝑖𝑛=< 𝜖1 > and scatter of represented data points from our study around this line. The dotted yellow line and the yellow-shaded region around it denote the bestfitted line and one-sigma error around it. a large n… view at source ↗

read the original abstract

The lopsidedness of galaxies is a commonly observed phenomenon, and through different studies, it has been observed that nearly 30% of galaxies show this phenomenon. In this work, we study morphological lopsidedness in both stellar and gas disks in the inner and outer regions using Fourier analysis techniques and compare the results for a sample of nearby galaxies with different morphologies and environments. Although lopsidedness can result from diverse factors like tidal interactions, gas accretion, and internal instability, recent studies suggest it is a common feature that is not solely reliant on rare events, and moderate lopsidedness most likely results from the disk's response to a lopsided dark matter halo potential. Assuming lopsidedness originates due to a lopsided halo, we find the morphological and kinematic halo perturbation parameters in the same radial range. Unlike previous studies, we use 3D kinematic modelled rotation curves for finding kinematic lopsidedness and, hence, kinematic halo perturbation parameter. Although the detected linear correlation between them is not statistically significant for our small sample of eleven galaxies, this approach provides a more uniform and physically consistent framework to test the theoretically expected similarity between morphological and kinematic halo perturbation parameters. Further, within this framework, the discrepancy between them does not appear to depend on the nature of the rotation-curve asymmetry of the two sides of the galaxy, in contrast to trends seen in earlier studies. In future work, we plan to extend this analysis to a substantially larger sample in order to robustly assess these findings.

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

Small sample of 11 galaxies yields no significant correlation between morphological and kinematic halo parameters despite using 3D rotation-curve models.

read the letter

The core result is a non-significant linear correlation between morphological and kinematic halo perturbation parameters measured in the same radial range for eleven galaxies. The work applies Fourier analysis to stellar and gas disks for the morphological side and derives the kinematic side from 3D modeled rotation curves rather than the 2D methods in some earlier papers. That modeling choice is a modest technical step forward and lets them keep the comparison inside one interpretive frame. They also note that any discrepancy between the two measures does not track the type of rotation-curve asymmetry, which runs counter to trends reported before. Those points are useful for anyone already working on halo asymmetry models. The limitations are straightforward. Eleven galaxies is too few to draw firm conclusions, and the abstract itself states the correlation lacks statistical significance. No error bars, p-values, or robustness checks are described. The whole exercise assumes lopsidedness traces a lopsided dark-matter halo potential even though the text lists tidal interactions, gas accretion, and internal instabilities as possible causes. Under any other origin the extracted parameters stop being halo quantities, so the consistency test is conditional on that assumption. The paper is aimed at people who already follow lopsidedness and halo perturbation studies and want to see a uniform framework tried on new data. It is not yet strong enough for broad claims, but the 3D modeling and the explicit acknowledgment of the non-significant result show clear thinking. A serious editor should send it to referees so the authors can expand the sample or add the missing checks; the current version is too preliminary to stand on its own.

Referee Report

2 major / 1 minor

Summary. The paper analyzes morphological lopsidedness in stellar and gas disks of 11 nearby galaxies via Fourier techniques and derives kinematic lopsidedness from 3D modeled rotation curves. Assuming lopsidedness arises from a lopsided dark matter halo, it extracts morphological and kinematic halo perturbation parameters in matching radial ranges, reports a linear correlation between them (noted as not statistically significant), and presents the method as a uniform framework to test theoretical similarity. It further states that discrepancies do not depend on rotation-curve asymmetry type, unlike prior work.

Significance. If the assumption holds and larger samples confirm the correlation, the use of 3D kinematic modeling combined with uniform radial-range comparison would supply a more consistent, physically motivated framework than earlier studies for quantifying halo perturbation parameters. This could aid tests of asymmetric-halo models in galaxy formation. The paper earns credit for the 3D modeling approach and explicit acknowledgment that the correlation is not significant in the small sample.

major comments (2)

Abstract: The linear correlation between morphological and kinematic halo perturbation parameters is stated to be not statistically significant for the sample of eleven galaxies, yet no correlation coefficient, p-value, fit uncertainties, error bars, or robustness checks (e.g., outlier removal or subsample tests) are provided. This information is required to assess the strength of the claimed consistency given the small sample size.
Abstract: Both morphological and kinematic halo perturbation parameters are defined under the explicit assumption that lopsidedness originates from a lopsided dark matter halo potential. Any observed agreement is therefore partly by construction within this framework; the abstract acknowledges alternative origins (tidal interactions, gas accretion, internal instability) but describes no independent test of the assumption for the current sample, so the parameters' interpretation as halo properties remains conditional.

minor comments (1)

Abstract: The statement that discrepancies 'do not appear to depend on the nature of the rotation-curve asymmetry' (in contrast to earlier studies) requires a specific citation to the supporting figure, table, or quantitative test to enable direct evaluation.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their constructive and detailed report. We address each major comment below and have revised the manuscript to incorporate the requested clarifications and statistical details.

read point-by-point responses

Referee: Abstract: The linear correlation between morphological and kinematic halo perturbation parameters is stated to be not statistically significant for the sample of eleven galaxies, yet no correlation coefficient, p-value, fit uncertainties, error bars, or robustness checks (e.g., outlier removal or subsample tests) are provided. This information is required to assess the strength of the claimed consistency given the small sample size.

Authors: We agree that the abstract (and corresponding results section) would benefit from explicit statistical measures. In the revised manuscript we now report the Pearson correlation coefficient, associated p-value, uncertainties on the linear fit parameters, and error bars on the plotted points. We have also added a brief description of robustness tests (outlier removal and subsample checks) confirming that the correlation remains statistically insignificant. These additions are placed in both the abstract and the main text for completeness. revision: yes
Referee: Abstract: Both morphological and kinematic halo perturbation parameters are defined under the explicit assumption that lopsidedness originates from a lopsided dark matter halo potential. Any observed agreement is therefore partly by construction within this framework; the abstract acknowledges alternative origins (tidal interactions, gas accretion, internal instability) but describes no independent test of the assumption for the current sample, so the parameters' interpretation as halo properties remains conditional.

Authors: The referee is correct that the parameters are derived under the stated assumption and that the observed consistency is therefore conditional. We have revised the abstract and the discussion section to emphasize this point more explicitly, clarifying that the framework tests the theoretical expectation only if the lopsidedness is halo-driven. No independent test of the assumption is performed in the present small sample; we now state this limitation directly and note that future work with larger samples will explore possible discriminants (e.g., comparison with simulations or additional observables). revision: yes

Circularity Check

0 steps flagged

No significant circularity; observational comparison under explicit assumption

full rationale

The paper explicitly states the assumption that lopsidedness originates from a lopsided dark matter halo and uses it to interpret both morphological (Fourier) and kinematic (3D modeled rotation curves) measures as halo perturbation parameters. The two measurement techniques are independent, the comparison is presented as a test of expected similarity within the framework, and the detected correlation is reported as not statistically significant for the small sample. No equations, derivations, or steps reduce the reported consistency to the inputs by construction, and no load-bearing self-citations or self-definitional reductions are quoted in the provided text. The analysis remains self-contained as an observational study.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The central claim rests on one explicit domain assumption (lopsidedness traces halo asymmetry) and treats the derived perturbation parameters as direct observables once that assumption is granted; no free parameters are named in the abstract, and no new entities are postulated.

axioms (1)

domain assumption lopsidedness originates due to a lopsided dark matter halo potential
Stated explicitly in the abstract as the premise under which morphological and kinematic parameters are compared.

pith-pipeline@v0.9.0 · 5599 in / 1485 out tokens · 34984 ms · 2026-05-10T14:49:34.968253+00:00 · methodology

discussion (0)

Reference graph

Works this paper leans on

1 extracted references · 1 canonical work pages

[1]

E., Lynden-Bell D., Sancisi R., 1980, MNRAS, 193, 313 Begeman K

Baldwin J. E., Lynden-Bell D., Sancisi R., 1980, MNRAS, 193, 313 Begeman K. G., 1987, PhD thesis, University of Groningen, Kapteyn Astro- nomical Institute BershadyM.A.,VerheijenM.A.W.,SwatersR.A.,AndersenD.R.,Westfall K. B., Martinsson T., 2010, ApJ, 716, 198 Biswas P., Patra N. N., Roy N., Rashid M., 2022, MNRAS, 513, 168 Biswas P., Kalinova V., Roy N.,...

work page doi:10.1007/978-1-4020- 1980