A Comparative Study of Local Galaxy Clusters: I. Derived X-ray Observables

TL;DR

This study compares X-ray derived properties of galaxy clusters from three different research groups, revealing systematic differences in mass estimates and other observables, with implications for cluster physics and cosmology.

Contribution

It provides a detailed comparison of X-ray cluster measurements across multiple datasets, highlighting systematic biases and differences in derived properties.

Findings

Mass differences up to 45% between datasets for high-redshift clusters.

Good agreement in gas mass estimates after aperture correction.

Observable differences of 5-15% in luminosity, temperature, and energy measures.

Abstract

We examine systematic differences in the derived X-ray properties of galaxy clusters as reported by three different groups: Vikhlinin et al. (2009a), Mantz et al. (2010b), and Planck Collaboration (2011b). The sample overlap between any two pairs of works ranges between 16 to 28 galaxy clusters in common. We find systematic differences in most reported properties, including the total cluster mass, M500. The most extreme case is an average 45% \pm 5% difference in cluster mass between the Planck Collaboration (2011b) and Mantz et al. (2010b), for clusters at z > 0.13 (averaged over 16 clusters). These mass differences induce differences in cluster observables defined within an R500 aperture. After accounting for aperture differences, we find very good agreement in gas mass estimates between the different groups. However, the soft-band X-ray luminosity, LX, core-excised spectroscopic temperature, TX, and gas thermal energy, YX = MgasTX display mean differences at the 5%-15% level. We also find that the low (z \leq 0.13) and high (z \geq 0.13) galaxy cluster samples in Planck Collaboration (2011b) appear to be systematically different: the YSZ/YX ratio for these two sub- samples is ln(YSZ/YX) = -0.06 \pm 0.04 and ln(YSZ/YX) = 0.08 \pm 0.04 for the low and high redshift sub-samples respectively.