Abstract
We present a detailed study of the integrated total hydrostatic mass profiles of the five most massive M500SZ < 5 × 1014 M⊙ galaxy clusters selected at z ∼ 1 via the Sunyaev–Zel’dovich effect. These objects represent an ideal laboratory to test structure formation models where the primary driver is gravity. Optimally exploiting spatially-resolved spectroscopic information from XMM-Newton and Chandra observations, we used both parametric (forward, backward) and non-parametric methods to recover the mass profiles, finding that the results are extremely robust when density and temperature measurements are both available. Our X-ray masses at R500 are higher than the weak lensing masses obtained from the Hubble Space Telescope (HST), with a mean ratio of 1.39−0.35+0.47. This offset goes in the opposite direction to that expected in a scenario where the hydrostatic method yields a biased, underestimated, mass. We investigated halo shape parameters such as sparsity and concentration, and compared to local X-ray selected clusters, finding hints for evolution in the central regions (or for selection effects). The total baryonic content is in agreement with the cosmic value at R500. Comparison with numerical simulations shows that the mass distribution and concentration are in line with expectations. These results illustrate the power of X-ray observations to probe the statistical properties of the gas and total mass profiles in this high mass, high-redshift regime.
Highlights
In the current ΛCDM paradigm, structure formation in the Universe is driven by the gravitational collapse of the dark matter component
The Backward parametric (BP) results indicate that while the NFW model is a good description in the case of relaxed objects (e.g. PLCK G266.6+27.3) and some perturbed systems (e.g. South Pole Telescope (SPT)−CL J2341−5119), the Einasto model is generally a better fit for our sample and is more able to fit a wider range of dynamical states
We found the same results by comparing the X-ray masses with the weak lensing masses centred on the SZ peak, M5W00LSZ, as shown in the bottom panels of Fig. 4
Summary
In the current ΛCDM paradigm, structure formation in the Universe is driven by the gravitational collapse of the dark matter component. Cosmological numerical simulations uniformly predict a quasi-universal cusped dark matter density profile, whose form only depends on mass and redshift. In the local (z 0.3) Universe, there is strong observational evidence for NFW-type dark and total matter density profiles with typical concentrations in line with expectations. Samples taken from such surveys are ideal for testing the theory of the dark matter collapse and its evolution. In this context, X-ray observations, while not the most accurate for measuring the mass because of the need for the assumption of hydrostatic equilibrium (HE), can give more precise results than other methods because of their good spatial resolution and signal-to-noise ratios.
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