Hydrostatic mass profiles in X-COP galaxy clusters

Abstract

Aims. We present the reconstruction of hydrostatic mass profiles in 13 X-ray luminous galaxy clusters that have been mapped in their X-ray and Sunyaev-Zeldovich (SZ) signals out to R200 for the XMM-Newton Cluster Outskirts Project (X-COP). Methods. Using profiles of the gas temperature, density, and pressure that have been spatially resolved out to median values of 0.9R500, 1.8R500, and 2.3R500, respectively, we are able to recover the hydrostatic gravitating mass profile with several methods and using different mass models. Results. The hydrostatic masses are recovered with a relative (statistical) median error of 3 % at R500 and 6% at R200. By using several different methods to solve the equation of the hydrostatic equilibrium, we evaluate some of the systematic uncertainties to be of the order of 5% at both R500 and R200. A Navarro-Frenk-White profile provides the best-fit in 9 cases out of 13; the remaining 4 cases do not show a statistically significant tension with it. The distribution of the mass concentration follows the correlations with the total mass predicted from numerical simulations with a scatter of 0.18 dex, with an intrinsic scatter on the hydrostatic masses of 0.15 dex. We compare them with the estimates of the total gravitational mass obtained through X-ray scaling relations applied to YX , gas fraction, and YSZ , and from weak lensing and galaxy dynamics techniques, and measure a substantial agreement with the results from scaling laws, from WL at both R500 and R200 (with differences below 15%), from cluster velocity dispersions. Instead, we find a significant tension with the caustic masses that tend to underestimate the hydrostatic masses by 40% at R200. We also compare these measurements with predictions from alternative models to the cold dark matter, like the emergent gravity and MOND scenarios, confirming that the latter underestimates hydrostatic masses by 40% at R1000, with a decreasing tension as the radius increases, and reaches ∼15% at R200, whereas the former reproduces M500 within 10%, but overestimates M200 by about 20%. Conclusions. The unprecedented accuracy of these hydrostatic mass profiles out to R200 allows us to assess the level of systematic errors in the hydrostatic mass reconstruction method, to evaluate the intrinsic scatter in the NFW c − M relation, and to robustly quantify differences among different mass models, different mass proxies, and different gravity scenarios.

The Three Hundred Project: Correcting for the hydrostatic-equilibrium mass bias in X-ray and SZ surveys

“…Since quantifying the level of gas inhomogeneities is feasible with current X-ray instruments, in this paper we investigate how these estimates can be used to statistically correct the mass bias at R 500 . We, furthermore, investigate an approach proposed almost a decade ago (e.g., Ameglio et al 2009) and recently adopted in observational samples (e.g., Ettori et al 2019): to include directly the pressure, which can be derived from SZ observations out to large radii, within the HE mass equation, under the assumption that clump pressure is close to the isobaric level of the ICM. These goals are pursued with a detailed investigation of the simulated clusters of 'The Three Hundred' Project (Cui et al 2018), analysed at z = 0.…”

Helium abundance (and H0) in X‐COP galaxy clusters

“…These selection criteria guarantee that a joint analysis of the X‐ray and SZ signals allows the reconstruction of the ICM properties out to R 200 (≈1.5 R 500 ) for all our targets. A complete description of the reduction and analysis of our proprietary X‐ray data and of the Planck SZ data is provided in Ghirardini et al () (see also Eckert et al ; Ettori et al ). Here we want only to remark that a proper treatment of the X‐ray surface brightness profiles, accounting for the median of the distribution of the counts per pixel in a given radial annulus instead of the mean (Eckert et al ; Zhuravleva et al ), guarantees in the X‐COP analysis against a relevant contribution from clumped gas that might systematically bias the estimate of the gas density (Equation (3)).…”

“…Total corrections on M gas , M hyd , and f gas , assuming H 0, CMB (green squares) and H 0, LMC (red diamonds). The correction on the hydrostatic mass is compared with the measured tension with weak‐lensing estimates for a subsample of six X‐COP objects (for details, see Ettori et al )…”

“…See also the appendix in Ghirardini et al (2019) to R 200 (≈1.5R 500 ) for all our targets. A complete description of the reduction and analysis of our proprietary X-ray data and of the Planck SZ data is provided in Ghirardini et al (2019) (see also Eckert et al 2019;Ettori et al 2019).…”

“…Thus, we can associate to a given H 0 the correction that propagates to the gas mass and to the hydrostatic mass through x, according to the scaling presented in Equation (2) and F I G U R E 5 Total corrections on M gas , M hyd , and f gas , assuming H 0,CMB (green squares) and H 0,LMC (red diamonds). The correction on the hydrostatic mass is compared with the measured tension with weak-lensing estimates for a subsample of six X-COP objects (for details, see Ettori et al 2019) accounting for the dependence both on x and H 0 . We show in Figure 5 the total correction on these quantities.…”