Dynamics of Void and its Shape in Redshift Space

TL;DR

This paper studies how spherical voids appear in redshift space within a cosmological model, revealing an elongation effect that can help measure cosmological parameters like the cosmological constant.

Contribution

It introduces a new analysis of void shapes in redshift space, showing their elongation along the line of sight and proposing a method to estimate cosmological parameters.

Findings

Void in redshift space appears as an elongated ellipse along the line of sight.

The shape deformation is opposite to the Kaiser effect.

Potential to evaluate cosmological constant from observed voids at z~1-2.

Abstract

We investigate the dynamics of a single spherical void embedded in a Friedmann-Lema\^itre universe, and analyze the void shape in the redshift space. We find that the void in the redshift space appears as an ellipse shape elongated in the direction of the line of sight (i.e., an opposite deformation to the Kaiser effect). Applying this result to observed void candidates at the redshift z~1-2, it may provide us with a new method to evaluate the cosmological parameters, in particular the value of a cosmological constant.