Local supercluster dynamics: external tidal impact of the PSC<i>z</i>sample traced by optimized numerical least action method

Romano-Díaz, Emilio; Branchini, E.; Weygaert, Rien van de

doi:10.1051/0004-6361:20042011

Cited by 11 publications

(11 citation statements)

References 86 publications

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“…Most methods aimed at describing the morphology of the large‐scale structure are either based directly on the galaxy distribution (e.g. Hoyle & Vogeley 2002; Romano‐Díaz & van de Weygaert 2007; Sousbie, Pichon & Kawahara 2011) or on the smoothed density field (e.g. Park et al 2005; Aragón‐Calvo et al 2007).…”

Section: Introductionmentioning

confidence: 99%

Reconstructing the cosmic velocity and tidal fields with galaxy groups selected from the Sloan Digital Sky Survey

Wang¹,

Mo²,

Yang³

et al. 2011

Monthly Notices of the Royal Astronomical Society

113

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Cosmic velocity and tidal fields are important for the understanding of the cosmic web and the environments of galaxies, and can also be used to constrain cosmology. In this paper, we reconstruct these two fields in the Sloan Digital Sky Survey (SDSS) volume from dark matter halos represented by galaxy groups. Detailed mock catalogues are used to test the reliability of our method against uncertainties arising from redshift distortions, survey boundaries, and false identifications of groups by our group finder. We find that both the velocity and tidal fields, smoothed on a scale of ∼ 2 h −1 Mpc, can be reliably reconstructed in the inner region (∼ 66%) of the survey volume.The reconstructed tidal field is used to split the cosmic web into four categories: clusters, filaments, sheets, and voids, depending on the sign of the eigenvalues of local tidal tensor. The reconstructed velocity field nicely shows how the flows are diverging from the centers of voids, and converging onto clusters, while sheets and filaments have flows that are convergent along one and two directions, respectively. We use the reconstructed velocity field and the Zel'dovich approximation to predict the mass density field in the SDSS volume as function of redshift, and find that the mass distribution closely follows the galaxy distribution even on small scales. We find a large-scale bulk flow of about 117 km s −1 in a very large volume, equivalent to a sphere 2 Huiyuan Wang et al.with a radius of ∼ 170 h −1 Mpc, which seems to be produced by the massive structures associated with the SDSS Great Wall. Finally, we discuss potential applications of our reconstruction to study the environmental effects of galaxy formation, to generate initial conditions for simulations of the local Universe, and to constrain cosmological models. The velocity, tidal and density fields in the SDSS volume, specified on a Cartesian grid with a spatial resolution of ∼ 700 h −1 kpc, are available from the authors upon request.

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Section: Introductionmentioning

confidence: 99%

Reconstructing the cosmic velocity and tidal fields with galaxy groups selected from the Sloan Digital Sky Survey

Wang¹,

Mo²,

Yang³

et al. 2011

Monthly Notices of the Royal Astronomical Society

113

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“…Voids are a dominant component of the cosmic web (see e.g. Romano‐Díaz & van de Weygaert 2007; Tully et al 2007), occupying most of the volume of space. In this paper we present evidence for significant alignments between neighbouring voids and establish the intimate dynamic link between voids and the cosmic tidal force field.…”

Section: Introductionmentioning

confidence: 99%

Alignment of voids in the cosmic web

Platen¹,

Weygaert²,

Jones³

2008

Monthly Notices RAS

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We investigate the shapes and mutual alignment of voids in the large‐scale matter distribution of a Λ cold dark matter (ΛCDM) cosmology simulation. The voids are identified using the novel watershed void finder (WVF) technique. The identified voids are quite non‐spherical and slightly prolate, with axis ratios in the order of c : b : a≈ 0.5 : 0.7 : 1. Their orientations are strongly correlated with significant alignments spanning scales >30 h−1 Mpc. We also find an intimate link between the cosmic tidal field and the void orientations. Over a very wide range of scales we find a coherent and strong alignment of the voids with the tidal field computed from the smoothed density distribution. This orientation–tide alignment remains significant on scales exceeding twice the typical void size, which shows that the long‐range external field is responsible for the alignment of the voids. This confirms the view that the large‐scale tidal force field is the main agent for the large‐scale spatial organization of the cosmic web.

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“…Another alternative consists of analysing velocity profiles, e.g. Romano‐Diaz & van de Weygaert (2007), for a review.…”

Section: Introductionmentioning

confidence: 99%

Phase-space structures - I. A comparison of 6D density estimators

Maciejewski

Colombi

Alard

et al. 2009

Monthly Notices of the Royal Astronomical Society

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In the framework of particle‐based Vlasov systems, this paper reviews and analyses different methods recently proposed in the literature to identify neighbours in 6D space and estimate the corresponding phase‐space density. Specifically, it compares smoothed particle hydrodynamics (SPH) methods based on tree partitioning to 6D Delaunay tessellation. This comparison is carried out on statistical and dynamical realizations of single halo profiles, paying particular attention to the unknown scaling, SG, used to relate the spatial dimensions to the velocity dimensions. It is found that, in practice, the methods with local adaptive metric provide the best phase‐space estimators. They make use of a Shannon entropy criterion combined with a binary tree partitioning and with subsequent SPH interpolation using 10–40 nearest neighbours. We note that the local scaling SG implemented by such methods, which enforces local isotropy of the distribution function, can vary by about one order of magnitude in different regions within the system. It presents a bimodal distribution, in which one component is dominated by the main part of the halo and the other one is dominated by the substructures of the halo. While potentially better than SPH techniques, since it yields an optimal estimate of the local softening volume (and therefore the local number of neighbours required to perform the interpolation), the Delaunay tessellation in fact generally poorly estimates the phase‐space distribution function. Indeed, it requires, prior to its implementation, the choice of a global scaling SG. We propose two simple but efficient methods to estimate SG that yield a good global compromise. However, the Delaunay interpolation still remains quite sensitive to local anisotropies in the distribution. To emphasize the advantages of 6D analysis versus traditional 3D analysis, we also compare realistic 6D phase‐space density estimation with the proxy proposed earlier in the literature, Q=ρ/σ3, where ρ is the local 3D (projected) density and 3σ2 is the local 3D velocity dispersion. We show that Q only corresponds to a rough approximation of the true phase‐space density, and is not able to capture all the details of the distribution in phase space, ignoring, in particular, filamentation and tidal streams.

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Local supercluster dynamics: external tidal impact of the PSCzsample traced by optimized numerical least action method

Cited by 11 publications

References 86 publications

Reconstructing the cosmic velocity and tidal fields with galaxy groups selected from the Sloan Digital Sky Survey

Reconstructing the cosmic velocity and tidal fields with galaxy groups selected from the Sloan Digital Sky Survey

Alignment of voids in the cosmic web

Phase-space structures - I. A comparison of 6D density estimators

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