A Comparative Study of Local Galaxy Clusters: II: X-ray and SZ Scaling Relations

TL;DR

This study compares X-ray and SZ galaxy cluster scaling relations, identifies systematic differences and modeling uncertainties, and proposes a multivariate model for consistent interpretation across observational catalogs.

Contribution

It introduces a multivariate scaling model that accounts for property covariance and scatter, improving the consistency of cluster scaling relations across different data sets.

Findings

Scaling relations agree after correcting for systematics and modeling uncertainties.

The predicted Ysz-Lx relation differs by approximately 25% from naive estimates.

The space density consistency test supports the validity of the scaling relations.

Abstract

We compare cluster scaling relations published for three different samples selected via X-ray and Sunyaev-Zel'dovich (SZ) signatures. We find tensions driven mainly by two factors: i) systematic differences in the X-ray cluster observables used to derive the scaling relations, and ii) uncertainty in the modeling of how the gas mass of galaxy clusters scales with total mass. All scaling relations are in agreement after accounting for these two effects. We describe a multivariate scaling model that enables a fully self-consistent treatment of multiple observational catalogs in the presence of property covariance, and apply this formalism when interpreting published results. The corrections due to scatter and observable covariance can be significant. For instance, our predicted Ysz-Lx scaling relation differs from that derived using the naive "plug in" method by \approx 25%. Finally, we test the mass normalization for each of the X-ray data sets we consider by applying a space density consistency test: we compare the observed REFLEX luminosity function to expectations from published Lx-M relations convolved with the mass function for a WMAP7 flat \Lambda CDM model.