The cosmic web and the orientation of angular momenta

Libeskind, Noam I.; Hoffman, Yehuda; Knebe, Alexander; Steinmetz, Matthias; Gottlöber, Stefan; Metuki, Ofer; Yepes, Gustavo

doi:10.1111/j.1745-3933.2012.01222.x

Cited by 106 publications

(126 citation statements)

References 34 publications

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“…The shear tensor is diagonalized and the eigenvalues (λ1, λ2, and λ3) and corresponding eigenvectors (e1 , e2 and e3 ) are then obtained. Eigenvalues are then ordered as λ1 > λ2 > λ3, denoting the strength of compression or expansion along the eigenvectors Libeskind et al 2012Libeskind et al , 2013. Note that the shear tensor's eigenvectors are non-directional lines, and as such their direction has a degeneracy of 180 degrees.…”

Section: Shear Tensormentioning

confidence: 99%

“…Methods to quantify the cosmic web abound (Stoica et al 2005;Shen et al 2006;Aragón-Calvo et al 2007;Hahn et al 2007;Sousbie et al 2008;Forero-Romero et al 2009;Hoffman et al 2012;Libeskind et al 2012Libeskind et al , 2013Tempel et al 2014a) depending on the data and problem at hand. In general, the methods based on simulations rely on a more complete knowledge of the cosmic fluid than what is usually available in observations.…”

Section: Introductionmentioning

confidence: 99%

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The alignment of galaxy spin with the shear field in observations

Pahwa

Libeskind

Tempel

et al. 2016

Mon. Not. R. Astron. Soc.

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Tidal torque theory suggests that galaxies gain angular momentum in the linear stage of structure formation. Such a theory predicts alignments between the spin of haloes and tidal shear field. However, non-linear evolution and angular momentum acquisition may alter this prediction significantly. In this paper, we use a reconstruction of the cosmic shear field from observed peculiar velocities combined with spin axes extracted from galaxies within 115 Mpc (∼ 8000 kms −1 ) from 2MRS catalog, to test whether or not galaxies appear aligned with principal axes of shear field. Although linear reconstructions of the tidal field have looked at similar issues, this is the first such study to examine galaxy alignments with velocity-shear field. Ellipticals in the 2MRS sample, show a statistically significant alignment with two of the principal axes of the shear field. In general, elliptical galaxies have their short axis aligned with the axis of greatest compression and perpendicular to the axis of slowest compression. Spiral galaxies show no signal. Such an alignment is significantly strengthened when considering only those galaxies that are used in velocity field reconstruction. When examining such a subsample, a weak alignment with the axis of greatest compression emerges for spiral galaxies as well. This result indicates that although velocity field reconstructions still rely on fairly noisy and sparse data, the underlying alignment with shear field is strong enough to be visible even when small numbers of galaxies are considered -especially if those galaxies are used as constraints in the reconstruction.

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Section: Shear Tensormentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The alignment of galaxy spin with the shear field in observations

Pahwa

Libeskind

Tempel

et al. 2016

Mon. Not. R. Astron. Soc.

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“…They suggested that the cosmic environments be classified into the four standard categories (i.e., knot, filament, sheet, void) by putting some positive threshold on the three eigenvalues of the local velocity shear tensor, and they demonstrated with a high-resolution N-body simulation that the web environments classified by their algorithm reproduced the expected images of the four categories (Libeskind et al 2012). However, there is no objective way to classify the cosmic web, and thus it is quite subjective to claim that the velocity shear field is an optimal tracer of the cosmic web.…”

Section: Introductionmentioning

confidence: 99%

Detection of the Velocity Shear Effect on the Spatial Distributions of the Galactic Satellites in Isolated Systems

Lee¹,

Choi²

2015

ApJ

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We report a detection of the effect of the large-scale velocity shear on the spatial distributions of the galactic satellites around the isolated hosts. Identifying the isolated galactic systems, each of which consists of a single host galaxy and its satellites, from the Seventh Data Release of the Sloan Digital Sky Survey and reconstructing linearly the velocity shear field in the local universe, we measure the alignments between the relative positions of the satellites from their isolated hosts and the principal axes of the local velocity shear tensors projected onto the plane of sky. We find a clear signal that the galactic satellites in isolated systems are located preferentially along the directions of the minor principal axes of the large-scale velocity shear field. Those galactic satellites that are spirals, are brighter, are located at distances larger than the projected virial radii of the hosts, and belong to the spiral hosts yield stronger alignment signals, which implies that the alignment strength depends on the formation and accretion epochs of the galactic satellites. It is also shown that the alignment strength is quite insensitive to the cosmic web environment, as well as the size and luminosity of the isolated hosts. Although this result is consistent with the numerical finding of Libeskind et al. based on an N-body experiment, owing to the very low significance of the observed signals, it remains inconclusive whether or not the velocity shear effect on the satellite distribution is truly universal.

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“…Hahn et al 2007;Libeskind et al 2012;Forero-Romero et al 2014). In as much as galaxy properties are determined by Figure 3.…”

Section: Halo Abundances In the Cosmic Webmentioning

confidence: 99%

REVEALING THE z ∼ 2.5 COSMIC WEB WITH 3D Lyα FOREST TOMOGRAPHY: A DEFORMATION TENSOR APPROACH

Lee

White

2016

ApJ

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Studies of cosmological objects should take into account their positions within the cosmic web of largescale structure. Unfortunately, the cosmic web has only been extensively mapped at low-redshifts (z < 1), using galaxy redshifts as tracers of the underlying density field. At z > 1, the required galaxy densities are inaccessible for the foreseeable future, but 3D reconstructions of Lyα forest absorption in closely-separated background QSOs and star-forming galaxies already offer a detailed window into z ∼ 2 − 3 large-scale structure. We quantify the utility of such maps for studying the cosmic web by using realistic z = 2.5 Lyα forest simulations matched to observational properties of upcoming surveys. A deformation tensor-based analysis is used to classify voids, sheets, filaments and nodes in the flux, which is compared to those determined from the underlying dark matter field. We find an extremely good correspondence, with 70% of the volume in the flux maps correctly classified relative to the dark matter web, and 99% classified to within 1 eigenvalue. This compares favorably to the performance of galaxy-based classifiers with even the highest galaxy densities from low-redshift surveys. We find that narrow survey geometries can degrade the cosmic web recovery unless the survey is 60 h −1 Mpc or 1 deg on the sky. We also examine halo abundances as a function of the cosmic web, and find a clear dependence as a function of flux overdensity, but little explicit dependence on the cosmic web. These methods will provide a new window on cosmological environments of galaxies at this very special time in galaxy formation, "high noon", and on overall properties of cosmological structures at this epoch.

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The cosmic web and the orientation of angular momenta

Cited by 106 publications

References 34 publications

The alignment of galaxy spin with the shear field in observations

The alignment of galaxy spin with the shear field in observations

Detection of the Velocity Shear Effect on the Spatial Distributions of the Galactic Satellites in Isolated Systems

REVEALING THE z ∼ 2.5 COSMIC WEB WITH 3D Lyα FOREST TOMOGRAPHY: A DEFORMATION TENSOR APPROACH

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