Testing the Reliability of Cluster Mass Indicators with a Systematics Limited Dataset

TL;DR

This study examines galaxy cluster mass indicators using X-ray data, revealing higher scatter than expected, likely due to hydrostatic mass assumptions, and highlights the need for systematic error analysis in cosmological applications.

Contribution

It identifies increased scatter in mass scaling relationships from hydrostatic mass estimates and emphasizes the importance of systematic error analysis in cluster studies.

Findings

2-3 times more scatter in mass scaling than expected

Larger range of temperature profile slopes at r_{500}

Weak dependence of gas mass fraction on cluster mass

Abstract

We present the mass-X-ray observable scaling relationships for clusters of galaxies using the XMM-Newton cluster catalog of Snowden et al. Our results are roughly consistent with previous observational and theoretical work, with one major exception. We find 2-3 times the scatter around the best fit mass scaling relationships as expected from cluster simulations or seen in other observational studies. We suggest that this is a consequence of using hydrostatic mass, as opposed to virial mass, and is due to the explicit dependence of the hydrostatic mass on the gradients of the temperature and gas density profiles. We find a larger range of slope in the cluster temperature profiles at r_{500} than previous observational studies. Additionally, we find only a weak dependence of the gas mass fraction on cluster mass, consistent with a constant. Our average gas mass fraction results argue for a closer study of the systematic errors due to instrumental calibration and analysis method variations. We suggest that a more careful study of the differences between various observational results and with cluster simulations is needed to understand sources of bias and scatter in cosmological studies of galaxy clusters.