A kinematic classification of the cosmic web
Abstract
A new approach for the classification of the cosmic web is presented. In extension of the previous work of Hahn et al. and ForeroRomero et al., the new algorithm is based on the analysis of the velocity shear tensor rather than the gravitational tidal tensor. The procedure consists of the construction of the shear tensor at each (grid) point in space and the evaluation of its three eigenvectors. A given point is classified to be either a void, sheet, filament or a knot according to the number of eigenvalues above a certain threshold, 0, 1, 2 or 3, respectively. The threshold is treated as a free parameter that defines the web. The algorithm has been applied to a dark matter only simulation of a box of side length 64 h^{1} Mpc and N = 1024^{3} particles within the framework of the 5year Wilkinson and Microwave Anisotropy Probe/Λ cold dark matter (ΛCDM) model. The resulting velocitybased cosmic web resolves structures down to ≲0.1 h^{1} Mpc scales, as opposed to the ≈1 h^{1} Mpc scale of the tidalbased web. The underdense regions are made of extended voids bisected by planar sheets, whose density is also below the mean. The overdense regions are vastly dominated by the linear filaments and knots. The resolution achieved by the velocitybased cosmic web provides a platform for studying the formation of haloes and galaxies within the framework of the cosmic web.
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 September 2012
 DOI:
 10.1111/j.13652966.2012.21553.x
 arXiv:
 arXiv:1201.3367
 Bibcode:
 2012MNRAS.425.2049H
 Keywords:

 cosmology: theory;
 dark matter;
 large scale of Universe;
 Astrophysics  Cosmology and Extragalactic Astrophysics
 EPrint:
 8 pages, 4 Figures, MNRAS Accepted 2012 June 19. Received 2012 May 10