Are there cool-core clusters at high-redshift? Chandra results and prospects with WFXT

TL;DR

This study investigates the evolution of cool-core galaxy clusters up to redshift 1.3 using Chandra data, finding a decline in cool-core fraction over time but evidence of well-formed cool-cores at high redshift, and discusses future prospects with WFXT.

Contribution

It introduces a new method to characterize cool-core strength in low S/N data and evaluates WFXT's potential to study high-redshift cool-core clusters.

Findings

Negative evolution of cool-core fraction with redshift.

Presence of well-formed cool-cores at z ~ 1.

WFXT's capability to detect and analyze high-z cool-core clusters.

Abstract

In this contribution we trace the evolution of cool-core clusters out to z~1.3 using high-resolution Chandra data of three representative cluster samples spanning different redshift ranges. Our analysis is based on the measurement of the surface brightness (SB) concentration, c_SB, which strongly anti-correlates with the central cooling time and allows us to characterize the cool-core strength in low S/N data. We confirm a negative evolution in the fraction of cool-core clusters with redshift, in particular for very strong cool-cores. Still, we find evidence for a large population of well formed cool-cores at z ~ 1. This analysis is potentially very effective in constraining the nature and the evolution of the cool-cores, once large samples of high-z clusters will be available. In this respect, we explore the potential of the proposed mission Wide Field X-ray Telescope (WFXT) to address this science case. We conclude that WFXT provides the best trade-off of angular resolution, sensitivity and covered solid angle in order to discover and fully characterize the cool-core cluster population up to z=1.5.