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arxiv: 2604.09983 · v1 · submitted 2026-04-11 · 🌌 astro-ph.GA

Environmental Dependence of Galaxy properties: A study of 341 Ring Galaxies in Cosmic Voids

Santosh Poudel , Binil Aryal This is my paper

Pith reviewed 2026-05-10 16:48 UTC · model grok-4.3

classification 🌌 astro-ph.GA
keywords ring galaxiescosmic voidsgalaxy morphologysecular evolutionenvironmental dependencevoid galaxiesstar formation ratesgalaxy colors
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The pith

Ring galaxies in cosmic voids are a distinct population shaped mainly by internal secular evolution under the weakest environmental gradients.

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

The paper studies the locations, morphologies, masses, colors, and star formation rates of 341 ring galaxies identified inside cosmic voids. It reports that over 90 percent lie away from void centers, that inner and outer pseudorings dominate the sample, and that these objects are systematically more massive, redder, and less actively star-forming than the average void galaxy. Only gentle gradients in mass and specific star formation rate appear from void core to edge. The authors conclude that ring galaxies represent a secularly evolved class whose formation is driven by internal dynamics even in the lowest-density large-scale environments. A reader would care because the result separates internal galaxy processes from the strong environmental effects usually invoked in denser regions.

Core claim

Ring galaxies in voids show a strong preference for locations away from void cores, with inner rings or pseudorings in 45 percent and outer pseudorings in 56 percent of the sample; relative to the general void population they are more massive, redder, and exhibit lower specific star formation rates, with only subtle radial trends in these quantities, indicating that they constitute a distinct, secularly evolved population whose properties are set by the weakest large-scale environmental gradients rather than by strong external interactions.

What carries the argument

Morphological classification of rings via the Buta CVRHS catalog applied to Galaxy Zoo 2 candidates, combined with VoidFinder void mapping, which enables direct comparison of ring properties against the broader void galaxy population.

If this is right

  • Ring formation proceeds primarily through internal dynamical instabilities such as bars even when external tidal forces are minimal.
  • Gentle density gradients across voids are enough to produce measurable but weak trends in stellar mass and star formation rate.
  • Ring galaxies can be used as clean tracers of secular evolution because they are little affected by the strong environmental processes that operate in clusters.
  • The observed preference for void edges implies a minimum density threshold below which ring structures become less common or less visible.

Where Pith is reading between the lines

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

  • Ring structures appear resilient across the full range of cosmic densities, which would imply that secular processes set morphology more universally than merger-driven models currently assume.
  • Similar ring populations should be detectable in other underdense regions such as the outskirts of superclusters, providing a testable extension.
  • Galaxy-evolution simulations that underweight internal secular channels would underpredict the abundance of ring features in low-density volumes.

Load-bearing premise

The Galaxy Zoo 2 decision tree plus Buta CVRHS classifications correctly identify genuine ring galaxies with little contamination or misidentification, and the VoidFinder catalog supplies an unbiased sample of void environments.

What would settle it

Deep imaging or spectroscopy showing that a large fraction of the 341 candidates display clear tidal tails, shells, or merger signatures would indicate external processes dominate, falsifying the secular-evolution interpretation.

Figures

Figures reproduced from arXiv: 2604.09983 by Binil Aryal, Santosh Poudel.

Figure 1
Figure 1. Figure 1: Images of four ring galaxies residing at outskirts of voids from our sample. NSAID 263999 (z = 0.07656, Void 435 ): An early-type lenticular galaxy (S0+) featuring an outer ring and an inner lens, with no bar; NSAID 238331 (z = 0.032417, Void 32): An intermediate-type spiral galaxy featuring an outer pseudoring intermediate bar and an inner pseudoring; NSAID 273968 (z = 0.057957, Void 658): An early type s… view at source ↗
Figure 2
Figure 2. Figure 2: Images of four ring galaxies residing on the onset of voids edges from our sample. NSAID 379096 (z = 0.032593, Void 689 ): An unbarred, transition type galaxy featuring an inner pseudoring marking the emergence of spiral structure within a largely smooth, lenticular like disk.; NSAID 243707 (z = 0.0341, Void 95): Inner Pseudoring structure; NSAID 56324 (z = 0.042552, Void 18): An unbarred to weakly barred … view at source ↗
Figure 3
Figure 3. Figure 3: Images of four ring galaxies residing on the cores of void from our sample. NSAID 383498 (z = 0.04399, Void 138 ): An intermediate type spiral galaxy featuring an close outer ring and an intermediate bar ; NSAID 530870 (z = 0.0422, Void 18): An early type spiral lenticular transition galaxy featuring an outer pseudoring, an intermediate bar, and inner spiral arms; NSAID 248444 (z = 0.0395, Void 516): Outer… view at source ↗
Figure 4
Figure 4. Figure 4: Environmental properties of ring galaxies in cosmic voids. Left: Distribution of distance fraction (r/R), where r is the distace from galaxy to the void center and R is the void effective radius, here the values near zero corresponds to the galaxies near void centers and values around one corresponds to galaxies near void edges. Middle: Distribution of absolute distances to void centers in Mpc/h. Right: Di… view at source ↗
Figure 5
Figure 5. Figure 5: Stellar mass distribution of void galaxies at different radial positions nearly constant across all bins, with g−r around 0.7–0.8 and u−r around 2.2–2.3. The blue fractions, defined by g−r < 0.7 and u−r < 2.3, also show no systematic trend with void radius, staying at approximately 30% and 55% respectively ( [PITH_FULL_IMAGE:figures/full_fig_p007_5.png] view at source ↗
Figure 6
Figure 6. Figure 6: Color properties of void ring galaxies [PITH_FULL_IMAGE:figures/full_fig_p008_6.png] view at source ↗
Figure 7
Figure 7. Figure 7: SFR of void ring galaxies. The dotted histogram is of average SFR values and black filled histogram is of median SFR values [PITH_FULL_IMAGE:figures/full_fig_p008_7.png] view at source ↗
Figure 8
Figure 8. Figure 8: sSFR of void ring galaxies.The dotted histogram is of average sSFR values and black filled histogram is of median sSFR values. of the void center might allow rings to persist for longer timescales, fading slowly due to secu￾lar diffusion. However, dynamical timescales are also longer in the lower-density halo potentials of the smallest void-center galaxies, potentially slowing the very internal evolution t… view at source ↗
read the original abstract

We investigate the morphological and physical properties of ring galaxies residing within cosmic voids. Using void catalogs from VoidFinder, ring candidates identified via the Galaxy Zoo 2 decision tree, and morphological classifications from the Buta (2017) CVRHS based catalog, we analyze a sample of 341 void ring galaxies and find a radial preference, with 91.5% located away from the void cores. Morphologically, inner rings and inner pseudorings account for 45.2% of the sample while outer pseudorings are even more common(56.3%) and outer rings appear in 17.9% of galaxies, which points to secular evolution driven by internal dynamics as the primary formation mechanism. Compared to the general void population, our sample ring galaxies are found to be more massive, redder, and have lower specific star formation rates. Subtle gradients in stellar mass and sSFR from void centers to edges also shows a gentle, density-dependent evolutionary progression. Our results show ring galaxies as a distinct, secularly evolved population shaped by the weakest large-scale environmental gradients

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.

Referee Report

2 major / 1 minor

Summary. The manuscript analyzes a sample of 341 ring galaxies in cosmic voids identified via VoidFinder catalogs, Galaxy Zoo 2 decision trees, and Buta CVRHS morphological classifications. It reports that 91.5% lie away from void cores, with morphological fractions (45.2% inner rings/pseudorings, 56.3% outer pseudorings, 17.9% outer rings) interpreted as evidence for secular evolution via internal dynamics; the ring galaxies are more massive, redder, and lower in sSFR than the general void population, with subtle radial gradients in stellar mass and sSFR from void centers to edges.

Significance. If the central observational results hold after addressing statistical and comparative gaps, the work would provide a useful census of ring galaxies in the lowest-density environments and support the viability of internal secular processes for ring formation even where large-scale tidal influences are minimal. The sample size is non-trivial for this rare morphological class, but the absence of any non-void control sample limits claims that the observed properties are specifically shaped by the weakest environmental gradients rather than by selection or universal processes.

major comments (2)
  1. [Abstract] Abstract: The claim that the sample forms 'a distinct, secularly evolved population shaped by the weakest large-scale environmental gradients' is not supported by the presented analysis, which is performed exclusively inside VoidFinder voids and compares only to the general void population. Without a quantitative contrast sample of ring galaxies in filaments, walls, or clusters, the secular signatures and weak internal gradients cannot be attributed specifically to the void environment.
  2. [Abstract] Abstract and results sections: The reported fractions (91.5% radial preference, 45.2% inner rings, 56.3% outer pseudorings) and property comparisons (higher mass, redder colors, lower sSFR) are given without error bars, confidence intervals, or statistical tests (e.g., binomial uncertainties on fractions or KS tests on mass/sSFR distributions). This absence prevents assessment of whether the offsets are significant or could arise from selection biases in the Galaxy Zoo 2 or Buta classifications.
minor comments (1)
  1. [Abstract] The abstract refers to 'subtle gradients' in stellar mass and sSFR but does not quantify their slopes, radial binning, or significance; a figure or table showing the binned trends with uncertainties would improve clarity.

Simulated Author's Rebuttal

2 responses · 1 unresolved

We thank the referee for the constructive review. We address the two major comments point by point below, revising the manuscript where the concerns are valid.

read point-by-point responses

  1. Referee: [Abstract] Abstract: The claim that the sample forms 'a distinct, secularly evolved population shaped by the weakest large-scale environmental gradients' is not supported by the presented analysis, which is performed exclusively inside VoidFinder voids and compares only to the general void population. Without a quantitative contrast sample of ring galaxies in filaments, walls, or clusters, the secular signatures and weak internal gradients cannot be attributed specifically to the void environment.

    Authors: We agree that the original abstract wording overstates the environmental specificity. Our study focuses on ring galaxies inside voids and contrasts them only with the general void population to demonstrate that secular internal processes operate even in the lowest-density regimes. This supports the viability of internal dynamics where large-scale tides are minimal, consistent with the reader's summary. However, without a non-void control sample we cannot claim the properties are uniquely shaped by void gradients. We have therefore revised the abstract to remove the phrase 'shaped by the weakest large-scale environmental gradients' and now state that the results indicate ring galaxies in voids constitute a distinct, secularly evolved population. revision: partial

  2. Referee: [Abstract] Abstract and results sections: The reported fractions (91.5% radial preference, 45.2% inner rings, 56.3% outer pseudorings) and property comparisons (higher mass, redder colors, lower sSFR) are given without error bars, confidence intervals, or statistical tests (e.g., binomial uncertainties on fractions or KS tests on mass/sSFR distributions). This absence prevents assessment of whether the offsets are significant or could arise from selection biases in the Galaxy Zoo 2 or Buta classifications.

    Authors: We acknowledge the omission of quantitative uncertainties and tests in the presented text. The revised manuscript now includes binomial uncertainties on all reported fractions and Kolmogorov-Smirnov tests on the stellar-mass, color, and sSFR distributions. These additions appear in both the abstract and results sections, allowing readers to evaluate significance and potential classification biases. revision: yes

standing simulated objections not resolved
  • The absence of a non-void control sample of ring galaxies, which would require a separate analysis outside the current scope.

Circularity Check

0 steps flagged

No circularity: purely observational statistical analysis on catalog data

full rationale

The paper selects 341 ring galaxies from VoidFinder + Galaxy Zoo 2 + Buta CVRHS catalogs, then reports descriptive statistics (locations, morphological fractions, mass/sSFR gradients) and comparisons to the general void population. No equations, fitted parameters, predictions, or derivations exist that could reduce outputs to inputs by construction. No self-citation chains or ansatzes are used to justify core claims. The analysis is self-contained against external catalogs and does not manufacture results via redefinition or renaming.

Axiom & Free-Parameter Ledger

0 free parameters · 3 axioms · 0 invented entities

The central claims rest on the reliability of three external catalogs rather than new parameters or entities derived within the paper.

axioms (3)
  • domain assumption VoidFinder catalogs accurately delineate cosmic voids without significant boundary or contamination errors.
    The radial preference analysis depends on void core versus edge definitions from this catalog.
  • domain assumption Galaxy Zoo 2 decision tree reliably flags true ring galaxies.
    The sample of 341 galaxies is defined by this citizen-science classification step.
  • domain assumption Buta (2017) CVRHS morphological classifications correctly distinguish inner rings, outer rings, and pseudorings.
    The reported fractions (45.2%, 17.9%, 56.3%) rely on these classifications.

pith-pipeline@v0.9.0 · 5495 in / 1522 out tokens · 54527 ms · 2026-05-10T16:48:45.554561+00:00 · methodology

discussion (0)

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Reference graph

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