Systematic Errors in Sunyaev-Zeldovich Surveys of Galaxy Cluster Velocities

TL;DR

This paper examines the potential and challenges of using Sunyaev-Zeldovich Effect-based galaxy cluster velocity surveys to constrain cosmology, highlighting systematic errors and their impact on dark energy measurements.

Contribution

It demonstrates that cluster velocity statistics are nearly independent of mass and discusses how to model and mitigate systematic errors in velocity measurements.

Findings

Cluster velocities closely trace large-scale velocity fields.

Velocity statistics are nearly independent of cluster mass.

Systematic errors can bias dark energy parameter estimation but are modelable.

Abstract

Galaxy cluster surveys compiled via the Sunyaev-Zeldovich Effect have the potential to place strong constraints on cosmology, and in particular the nature of dark energy. Here we consider cluster velocity surveys using kinetic Sunyaev-Zeldovich measurements. Cluster velocities closely trace the large-scale velocity field independent of cluster mass; we demonstrate that two useful cluster velocity statistics are nearly independent of cluster mass, in marked contrast to cluster number count statistics. On the other hand, cluster velocity determinations from three-band observations of Sunyaev-Zeldovich distortions can require additional cluster data or assumptions, and are complicated by microwave emission from dusty galaxies and radio sources, which may be correlated with clusters. Systematic errors in velocity due to these factors can give substantial biases in determination of dark energy parameters, although large cluster velocity surveys will contain enough information that the errors can be modeled using the data itself, with little degradation in cosmological constraints.