On the relative bias of void tracers in the Dark Energy Survey

TL;DR

This paper investigates the relative bias between different tracers of large-scale structure around cosmic voids, confirming a linear relation that varies with void size, using simulations and DES data, and provides a new void catalogue.

Contribution

It demonstrates that the relation between galaxy and cluster density profiles around voids is linear and environment-dependent, supported by simulations and DES data, and introduces a void catalogue from photometric data.

Findings

The density profiles of different tracers around voids are linearly related.

The relative bias varies with void size, being higher for smaller voids.

A new catalogue of 3D voids from photometric survey data is presented.

Abstract

Luminous tracers of large-scale structure are not entirely representative of the distribution of mass in our Universe. As they arise from the highest peaks in the matter density field, the spatial distribution of luminous objects is biased towards those peaks. On large scales, where density fluctuations are mild, this bias simply amounts to a constant offset in the clustering amplitude of the tracer, known as linear bias. In this work we focus on the relative bias between galaxies and galaxy clusters that are located inside and in the vicinity of cosmic voids, extended regions of relatively low density in the large-scale structure of the Universe. With the help of hydro-dynamical simulations we verify that the relation between galaxy and cluster overdensity around voids remains linear. Hence, the void-centric density profiles of different tracers can be linked by a single multiplicative constant. This amounts to the same value as the relative linear bias between tracers for the largest voids in the sample. For voids of small sizes, which typically arise in higher density regions, this constant has a higher value, possibly showing an environmental dependence similar to that observed for the linear bias itself. We confirm our findings by analysing mocks and data obtained during the first year of observations by the Dark Energy Survey. As a side product, we present the first catalogue of three-dimensional voids extracted from a photometric survey with a controlled photo-z uncertainty. Our results will be relevant in forthcoming analyses that attempt to use voids as cosmological probes.