Evidence for Filamentarity in the Las Campanas Redshift Survey

Bharadwaj, Somnath; Sahni, Varun; Sathyaprakash, B. S.; Shandarin, Sergei F.; Yess, Capp

doi:10.1086/308163

Cited by 60 publications

(89 citation statements)

References 18 publications

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“…Note that all visual features across the boundaries in the two bottom panels (Shuffled data) are chance filaments. the number of holes (genus) stabilizes and then decreases (Bharadwaj et al 2000). For the À3 slice, this ratio stabilizes around 140 h À1 Mpc at FF $ 0:4.…”

Section: Discussionmentioning

confidence: 88%

“…originally defined in Bharadwaj et al (2000), to quantify the shape of the superclusters in the quasi-two-dimensional slices of the LCRS. By definition 0 F 1, which quantifies the degree of filamentarity of a cluster, with F ¼ 1 indicating a filament and F ¼ 0 indicating a square (while dealing with a density field defined on a grid).…”

Section: Analysis and Resultsmentioning

confidence: 99%

“…This raises the question of whether the filamentary features that appear to span scales larger than 100 h À1 Mpc are statistically significant features of the galaxy distribution, or whether they are mere artifacts arising from chance alignment of the galaxies. A quantitative estimator of filamentary structure, Shapefinder, was defined (Bharadwaj et al 2000) to provide a measure of the average filamentarity for a point distribution in two dimensions. (See for general introduction to Shapefinders and Sheth et al 2003 for the application of Shapefinders to three-dimensional simulations of structure formation.)…”

Section: Introductionmentioning

confidence: 99%

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The Size of the Longest Filaments in the Universe

Bharadwaj

Bhavsar

Sheth

2004

ApJ

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We analyze the filamentarity in the Las Campanas redshift survey (LCRS) and determine the length scale at which filaments are statistically significant. The largest length scale at which filaments are statistically significant, real objects is between 70 and 80 h À1 Mpc for the LCRS À3 slice. Filamentary features longer than 80 h À1 Mpc, although identified, are not statistically significant; they arise from chance alignments. For the five other LCRS slices, filaments of lengths 50-70 h À1 Mpc are statistically significant, but not beyond. These results indicate that while individual filaments up to 80 h À1 Mpc are statistically significant, the impression of structure on larger scales is a visual effect. On scales larger than 80 h À1 Mpc, the filaments interconnect by statistical chance to form the filament-void network. The reality of the 80 h À1 Mpc features in the À3 slice makes them the longest coherent features in the LCRS. While filaments are a natural outcome of gravitational instability, any numerical model that attempts to describe the formation of large-scale structure in the universe must produce coherent structures on scales that match these observations.

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Section: Discussionmentioning

confidence: 88%

Section: Analysis and Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The Size of the Longest Filaments in the Universe

Bharadwaj

Bhavsar

Sheth

2004

ApJ

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“…The area, length, and level-crossing statistics directly quantify the amount of contour surfaces (Ryden 1988b;Ryden et al 1989;Torres 1994). The Minkowski functionals (Mecke, Buchert, & Wagner 1994;Kerscher et al 1998;Bharadwaj et al 2000), which are closely related to the above statistics, are also applied to smoothed cosmic fields (Winitzki & Kosowsky 1997;Naselsky & Novikov 1998;Schmalzing & Gorski 1998;Schmalzing et al 1999;Schmalzing & Diaferio 2000). These statistics of smoothed density fields are considered as powerful descriptors of the statistical information of the universe.…”

Section: Introductionmentioning

confidence: 99%

Statistics of Smoothed Cosmic Fields in Perturbation Theory. I. Formulation and Useful Formulae in Second‐Order Perturbation Theory

Matsubara¹

2003

ApJ

133

166

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We formulate a general method for perturbative evaluations of statistics of smoothed cosmic fields and provide useful formulae for application of the perturbation theory to various statistics. This formalism is an extensive generalization of the method used by Matsubara, who derived a weakly nonlinear formula of the genus statistic in a three-dimensional density field. After describing the general method, we apply the formalism to a series of statistics, including genus statistics, level-crossing statistics, Minkowski functionals, and a density extrema statistic, regardless of the dimensions in which each statistic is defined. The relation between the Minkowski functionals and other geometrical statistics is clarified. These statistics can be applied to several cosmic fields, including three-dimensional density field, three-dimensional velocity field, twodimensional projected density field, and so forth. The results are detailed for second-order theory of the formalism. The effect of the bias is discussed. The statistics of smoothed cosmic fields as functions of rescaled threshold by volume fraction are discussed in the framework of second-order perturbation theory. In CDMlike models, their functional deviations from linear predictions plotted against the rescaled threshold are generally much smaller than that plotted against the direct threshold. There is still a slight meatball shift against rescaled threshold, which is characterized by asymmetry in depths of troughs in the genus curve. A theory-motivated asymmetry factor in the genus curve is proposed.

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“…This procedure, however, does not distinguish between different levels of compactness or filamentarity. Other approaches have been proposed to characterize the geometry of complex structures, most notably Minkowsky functionals (Bharadwaj et al 2000;Basilakos 2003;Einasto et al 2007;Costa-Duarte et al 2011), surface modeling via triangulated networks (Sheth et al 2003) and shapefinders of several kinds (e.g. Sahni et al 1998;Aragón-Calvo et al 2007).…”

Section: Structures In the High Density Regionsmentioning

confidence: 99%

Clues on void evolution – III. Structure and dynamics in void shells

Ruiz

Paz

Lares

et al. 2015

Monthly Notices of the Royal Astronomical Society

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Inspired on the well known dynamical dichotomy predicted in voids, where some underdense regions expand whereas others collapse due to overdense surrounding regions, we explored the interplay between the void inner dynamics and its large scale environment. The environment is classified depending on its density as in previous works. We analyse the dynamical properties of void-centered spherical shells at different void-centric distances depending on this classification. The above dynamical properties are given by the angular distribution of the radial velocity field, its smoothness, the field dependence on the tracer density and shape, and the field departures from linear theory. We found that the velocity field in expanding voids follows more closely the linear prediction, with a more smooth velocity field. However when using velocity tracers with large densities such deviations increase. Voids with sizes around 18hMpc are in a transition regime between regions with expansion overpredicted and underpredicted from linear theory. We also found that velocity smoothness increases as the void radius, indicating the laminar flow dominates the expansion of larger voids (more than 18hMpc). The correlations observed suggest that nonlinear dynamics of the inner regions of voids could be dependent on the evolution of the surrounding structures. These also indicate possible scale couplings between the void inner expansion and the large scale regions where voids are embedded. These results shed some light to the origin of nonlinearities in voids, going beyond the fact that voids just quickly becomes nonlinear as they become emptier.

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Evidence for Filamentarity in the Las Campanas Redshift Survey

Cited by 60 publications

References 18 publications

The Size of the Longest Filaments in the Universe

The Size of the Longest Filaments in the Universe

Statistics of Smoothed Cosmic Fields in Perturbation Theory. I. Formulation and Useful Formulae in Second‐Order Perturbation Theory

Clues on void evolution – III. Structure and dynamics in void shells

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