Galaxy cluster scaling relations measured with APEX-SZ

TL;DR

This study measures the Sunyaev-Zel'dovich effect in 42 galaxy clusters using APEX-SZ, analyzing the scaling relations between SZE and X-ray properties to understand cluster physics and evolution.

Contribution

It provides new SZE measurements for 42 clusters and compares these with X-ray observables, revealing the impact of analysis variability and supporting models with cooling and feedback.

Findings

Scaling relations are consistent with self-similar gravitational models.

Variability in X-ray analysis affects normalization of scaling relations.

Intrinsic scatter in the Y-Y_X relation is approximately 28%.

Abstract

We present thermal Sunyaev-Zel'dovich effect (SZE) measurements for 42 galaxy clusters observed at 150 GHz with the APEX-SZ experiment. For each cluster, we model the pressure profile and calculate the integrated Comptonization $Y$ to estimate the total thermal energy of the intracluster medium (ICM). We compare the measured $Y$ values to X-ray observables of the ICM from the literature (cluster gas mass $M_{\rm{gas}}$, temperature $T_X$, and $Y_X =M_{\rm{gas}}T_X$) that relate to total cluster mass. We measure power law scaling relations, including an intrinsic scatter, between the SZE and X-ray observables for three subsamples within the set of 42 clusters that have uniform X-ray analysis in the literature. We observe that differences between these X-ray analyses introduce significant variability into the measured scaling relations, particularly affecting the normalization. For all three subsamples, we find results consistent with a self-similar model of cluster evolution dominated by gravitational effects. Comparing to predictions from numerical simulations, these scaling relations prefer models that include cooling and feedback in the ICM. Lastly, we measure an intrinsic scatter of $\sim28$ per cent in the $Y-Y_X\,$ scaling relation for all three subsamples.