Voids in Ly{\alpha} Forest Tomographic Maps

TL;DR

This paper introduces a new method for identifying cosmic voids in high-redshift Lyα forest tomographic maps, demonstrating its effectiveness through simulations and discussing potential cosmological applications.

Contribution

The authors develop and validate a novel void-finding technique for high-redshift Lyα forest maps, providing tools and forecasts for future large-area surveys.

Findings

Void properties at high redshift are similar to low-redshift but smaller and steeper.

Good agreement between voids in tomographic maps and density fields for voids larger than 6 h^{-1} Mpc.

The method enables detection of about 100 high-redshift voids in the CLAMATO survey area.

Abstract

We present a new method of finding cosmic voids using tomographic maps of Ly{\alpha} forest flux. We identify cosmological voids with radii of 2 - 12 $h^{-1}$Mpc in a large N-body simulation at $z = 2.5$, and characterize the signal of the high-redshift voids in density and Ly{\alpha} forest flux. The void properties are similar to what has been found at lower redshifts, but they are smaller and have steeper radial density profiles. Similarly to what has been found for low-redshift voids, the radial velocity profiles have little scatter and agree very well with the linear theory prediction. We run the same void finder on an ideal Ly{\alpha} flux field and tomographic reconstructions at various spatial samplings. We compare the tomographic map void catalogs to the density void catalog and find good agreement even with modest-sized voids ($r > 6 \, h^{-1}$Mpc). Using our simple void-finding method, the configuration of the ongoing CLAMATO survey covering 1 deg$^2$ would provide a sample of about 100 high-redshift voids. We also provide void-finding forecasts for larger area surveys, and discuss how these void samples can be used to test modified gravity models, study high-redshift void galaxies, and to make an Alcock-Paczynski measurement. To aid future work in this area, we provide public access to our simulation products, catalogs, and sample tomographic flux maps.