Optimal void finders in weak lensing maps

Monthly Notices of the Royal Astronomical Society, vol. 500, pp. 2417–2439

Abstract

ABSTRACT Cosmic voids are a key component of the large-scale structure that contain a plethora of cosmological information. Typically, voids are identified from the underlying galaxy distribution, which is a biased tracer of the total matter field. Previous works have shown that 2D voids identified in weak lensing (WL) maps – WL voids – correspond better to true underdense regions along the line of sight. In this work, we study how the properties of WL voids depend on the choice of void finder, by adapting several popular void finders. We present and discuss the differences between identifying voids directly in the convergence maps, and in the distribution of WL peaks. Particular effort has been made to test how these results are affected by galaxy shape noise (GSN), which is a dominant source of noise in WL observations. By studying the signal-to-noise ratios (S/N) for the tangential shear profile of each void finder, we find that voids identified directly in the convergence maps have the highest S/N but are also the ones most affected by GSN. Troughs are least affected by noise, but also have the lowest S/N. The tunnel algorithm, which identifies voids in the distribution of WL peaks, represents a good compromise between finding a large tangential shear S/N and mitigating the effect of GSN.

Authors 4

1. Christopher T Davies corresponding

   Durham University

   Affiliation as printed

   Institute for Computational Cosmology, Department of Physics, Durham University, South Road, Durham DH1 3LE, UK

2. E. Paillas

   Pontificia Universidad Católica de Chile

   Affiliation as printed

   Centro de Astro-Ingeniería, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860 Santiago, Chile

   Instituto de Astrofísica, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, Santiago, Chile

3. Marius Cautun Aachen Leiden Observatory

   Leiden University · Leiden Observatory

   Affiliation as printed

   Leiden Observatory, Leiden University, P.O. Box 9513, NL-2300 RA Leiden, the Netherlands

4. Baojiu Li

   Durham University

   Affiliation as printed

   Institute for Computational Cosmology, Department of Physics, Durham University, South Road, Durham DH1 3LE, UK