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Shapes and Alignments of Galaxy Cluster Halos
Astrophysics · Submitted 3 Aug 2004
abstract compiled · 2026-09-23 · no language-model review
The authors' main claim We investigate mark correlations of halo pair orientations using two measures: a simple scalar product shows $\ge 1%$ alignment extending to $30 \hinv \mpc$ while a filamentary statistic exhibits non-random alignment extending to scales $\sims 200 \hinv \mpc$, ten times the sample two-point correlation length and well into the regime of negative two-point correlation.
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The abstract, sentence by sentence
We present distribution functions and spatial correlations of the shapes of dark matter halos derived from Hubble Volume simulations of a LambdaCDM universe. We measure both position and velocity shapes within spheres encompassing mean density 200 times the critical value, and calibrate small-N systematic errors using Poisson realizations of isothermal spheres and higher resolution simulations. For halos more massive than 3x10^{14} Msun/h, the shape distribution function peaks at (minor/major, intermediate/major) axial ratios of (0.64,0.76) in position, and is rounder in velocity, peaking at (0.72,0.82). Halo shapes are rounder at lower mass and/or redshift; the mean minor axis ratio in position follows <c/a>(M,z) = c_{15,0} [1-\alpha\ln(M/10^{15}Msun/h)] (1+z)^{-\epsilon}, with c_{15,0}=0.631 \pm 0.001, \alpha=0.023 \pm 0.002 and \epsilon=0.086 \pm 0.004. Position and velocity principal axes are well aligned in direction, with median alignment angle $22^\circ$, and the axial ratios in these spaces are correlated in magnitude. We investigate mark correlations of halo pair orientations using two measures: a simple scalar product shows $\ge 1%$ alignment extending to $30 \hinv \mpc$ while a filamentary statistic exhibits non-random alignment extending to scales $\sims 200 \hinv \mpc$, ten times the sample two-point correlation length and well into the regime of negative two-point correlation. Cluster shapes are unaffected by the large-scale environment; the shape distribution of supercluster members is consistent with that of the general population.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | We present distribution functions and spatial correlations of the shapes of dark matter halos derived from Hubble Volume simulations of a LambdaCDM universe. | contribution 1.00 | 0.95 | 0.07 | asserted 0.99 |
| s1 | We measure both position and velocity shapes within spheres encompassing mean density 200 times the critical value, and calibrate small-N systematic errors using Poisson realizations of isothermal spheres and higher resolution simulations. | method 1.00 | 0.96 | 0.03 | asserted 1.00 |
| s2 | For halos more massive than 3x10^{14} Msun/h, the shape distribution function peaks at (minor/major, intermediate/major) axial ratios of (0.64,0.76) in position, and is rounder in velocity, peaking at (0.72,0.82). | result 1.00 | 0.95 | 0.14 | asserted 1.00 |
| s3 | Halo shapes are rounder at lower mass and/or redshift; the mean minor axis ratio in position follows <c/a>(M,z) = c_{15,0} [1-\alpha\ln(M/10^{15}Msun/h)] (1+z)^{-\epsilon}, with c_{15,0}=0.631 \pm 0.001, \alpha=0.023 \pm 0.002 and \epsilon=0.086 \pm 0.004. | result 1.00 | 0.94 | 0.16 | asserted 1.00 |
| s4 | Position and velocity principal axes are well aligned in direction, with median alignment angle $22^\circ$, and the axial ratios in these spaces are correlated in magnitude. | result 1.00 | 0.94 | 0.11 | asserted 1.00 |
| s5 | We investigate mark correlations of halo pair orientations using two measures: a simple scalar product shows $\ge 1%$ alignment extending to $30 \hinv \mpc$ while a filamentary statistic exhibits non-random alignment extending to scales $\sims 200 \hinv \mpc$, ten times the sample two-point correlation length and well into the regime of negative two-point correlation. | result 0.95 | 0.95 | 0.27 | asserted 1.00 |
| s6 | Cluster shapes are unaffected by the large-scale environment; the shape distribution of supercluster members is consistent with that of the general population. | result 1.00 | 0.90 | 0.14 | asserted 0.92 |
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The paper
Original abstract
We present distribution functions and spatial correlations of the shapes of dark matter halos derived from Hubble Volume simulations of a LambdaCDM universe. We measure both position and velocity shapes within spheres encompassing mean density 200 times the critical value, and calibrate small-N systematic errors using Poisson realizations of isothermal spheres and higher resolution simulations. For halos more massive than 3x10^{14} Msun/h, the shape distribution function peaks at (minor/major, intermediate/major) axial ratios of (0.64,0.76) in position, and is rounder in velocity, peaking at (0.72,0.82). Halo shapes are rounder at lower mass and/or redshift; the mean minor axis ratio in position follows <c/a>(M,z) = c_{15,0} [1-\alpha\ln(M/10^{15}Msun/h)] (1+z)^{-\epsilon}, with c_{15,0}=0.631 \pm 0.001, \alpha=0.023 \pm 0.002 and \epsilon=0.086 \pm 0.004. Position and velocity principal axes are well aligned in direction, with median alignment angle $22^\circ$, and the axial ratios in these spaces are correlated in magnitude. We investigate mark correlations of halo pair orientations using two measures: a simple scalar product shows $\ge 1%$ alignment extending to $30 \hinv \mpc$ while a filamentary statistic exhibits non-random alignment extending to scales $\sims 200 \hinv \mpc$, ten times the sample two-point correlation length and well into the regime of negative two-point correlation. Cluster shapes are unaffected by the large-scale environment; the shape distribution of supercluster members is consistent with that of the general population.
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4 arXiv papers cite this in 6 sentences
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Assuming that the HSE assumption holds for a large cluster sample, we compare our results with N-body simulation studies by [ref] , [ref] , and [ref] .
The three-dimensional shapes of the galaxy cluster intracluster medium in eRASS1 · Conclusions · 0.99
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