Chandra Cluster Cosmology Project II: Samples and X-ray Data Reduction

TL;DR

This paper presents measurements of galaxy cluster mass functions at different redshifts using Chandra X-ray data, providing updated calibrations and analyzing their evolution for cosmological insights.

Contribution

It offers new calibration relations between X-ray indicators and cluster mass, and first measurements of the evolving L_X-Mtot relation from a complete cluster sample.

Findings

Measured evolution of cluster number density by a factor of 5.0 ± 1.2 from z=0 to 0.5.

Provided updated calibration of X-ray to mass relations based on relaxed clusters.

Quantified systematic uncertainties and discussed likelihood calculations.

Abstract

We discuss the measurements of the galaxy cluster mass functions at z=~0.05 and z=~0.5 using high-quality Chandra observations of samples derived from the ROSAT PSPC All-Sky and 400deg^2 surveys. We provide a full reference for the data analysis procedures, present updated calibration of relations between the total cluster mass and its X-ray indicators (T_X, Mgas, and Y_X) based on a subsample of low-z relaxed clusters, and present a first measurement of the evolving L_X-Mtot relation (with Mtot estimated from Y_X) obtained from a well-defined statistically complete cluster sample and with appropriate corrections for the Malmquist bias applied. Finally, we present the derived cluster mass functions, estimate the systematic uncertainties in this measurement, and discuss the calculation of the likelihood function. We confidently measure the evolution in the cluster comoving number density at a fixed mass threshold, e.g., by a factor of 5.0 +- 1.2 at M_500=2.5e14 h^-1 Msun between z=0 and 0.5. This evolution reflects the growth of density perturbations and can be used for the cosmological constraints complementing those from the distance-redshift relation.