A gravitational lensing detection of filamentary structures connecting luminous red galaxies

¹ Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK
e-mail: qx211@roe.ac.uk
² Department of Astrophysics, University of Oxford, Keble Road, Oxford OX1 3RH, UK
e-mail: naomi.robertson@physics.ox.ac.uk
³ German Centre for Cosmological Lensing, Astronomisches Institut, Ruhr-Universität Bochum, Universitätsstr, Bochum, Germany
⁴ Kavli Institute for Particle Astrophysics & Cosmology, Stanford University, PO Box 2450, Stanford, CA 94305, USA
⁵ Argelander-Institut für Astronomie, Universitẗ Bonn, Auf dem Hügel 71, 53121 Bonn, Germany
⁶ Leiden Observatory, Leiden University, PO Box 9513, 2300 Leiden, The Netherlands
⁷ Instituto de Física, Pontificia Universidad Católica de Valparaíso, Casilla, 4059 Valparaíso, Chile

Received: 12 September 2019
Accepted: 26 November 2019

Abstract

We present a weak lensing detection of filamentary structures in the cosmic web, combining data from the Kilo-Degree Survey, the Red Cluster Sequence Lensing Survey, and the Canada-France-Hawaii Telescope Lensing Survey. The line connecting luminous red galaxies with a separation of 3 − 5 h⁻¹ Mpc was chosen as a proxy for the location of filaments. We measured the average weak lensing shear around ∼11 000 candidate filaments selected in this way from the Sloan Digital Sky Survey. After nulling the shear induced by the dark matter haloes around each galaxy, we reported a 3.4σ detection of an anisotropic shear signal from the matter that connects them. Adopting a filament density profile, motivated from N-body simulations, the average density at the centre of these filamentary structures was found to be 15 ± 4 times the critical density.