Temperature Structure and Mass-Temperature Scatter In Galaxy Clusters

TL;DR

This study evaluates the effectiveness of the T_HBR temperature ratio as an indicator of scatter in the galaxy cluster mass-temperature relation using simulated data, finding only a modest correlation.

Contribution

It introduces and tests T_HBR as a potential measure of cluster substructure and scatter in the mass-temperature relation using simulations.

Findings

T_HBR is correlated with deviations from the mean M-T_X relation.

The correlation between T_HBR and scatter is modest.

T_HBR alone may not be a strong indicator of mass-temperature scatter.

Abstract

Precision cosmology studies based on wide-field surveys of galaxy clusters benefit from constraints on intrinsic scatter in mass-observable relationships. In principle, two-parameter models combining direct measurements of galaxy cluster structural variation with mass proxies such as X-ray luminosity and temperature can be used to constrain scatter in the relationship between the mass proxy and the cluster's halo mass and to measure the redshift evolution of that scatter. One candidate for quantifying cluster substructure is the ICM temperature inhomogeneity inferred from X-ray spectral properties, an example of which is T_HBR, the ratio of hardband to broadband spectral-fit temperatures. In this paper we test the effectiveness of T_HBR as an indicator of scatter in the mass-temperature relation using 118 galaxy clusters simulated with radiative cooling and feedback. We find that, while T_HBR is correlated with clusters' departures \delta lnT_X from the mean M-T_X relation, the effect is modest.