A comparative study of local galaxy clusters – I. Derived X-ray observables

We examine systematic differences in the derived X-ray properties of galaxy clusters as reported by three different groups: Vikhlinin et al., Mantz et al. and Plank Collaboration. The sample overlap between any two pairs of works ranges between 16 to 28 galaxy clusters. We find systematic differences in most reported X-ray properties, including the total cluster mass, M 500 . The most extreme case is an average 45 5 per cent difference in cluster mass between the Plank Collaboration and Mantz et al., for clusters at z > 0.13 (averaged over 16 clusters). These differences also induce differences in cluster observables defined within an R 500 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, L X , core-excised spectroscopic temperature, T X , and gas thermal energy, Y X = M gas T X display mean differences at the 5-15 per cent level. We also find that the low (z 0.13) and high (z 0.13) redshift galaxy cluster samples in Plank Collaboration appear to be systematically different: the Y SZ /Y X ratio for each of these two sub-samples is ln (Y SZ /Y X ) = -0.06 0.04 and ln (Y SZ /Y X ) = 0.08 0.04, respectively.