Dark Matter Halo Profiles of Massive Clusters: Theory Versus Observations

Abstract

Dark matter-dominated cluster-scale halos act as an important cosmological probe and provide a key testing ground for structure formation theory. Focusing on their mass profiles, we have carried out (gravity-only) simulations of the concordance ΛCDM cosmology, covering a mass range of 2 × 10 12 − 2 × 10 15 h −1 M ⊙ and a redshift range of z = 0 − 2, while satisfying the associated requirements of resolution and statistical control. When fitting to the Navarro-Frenk-White profile, our concentration-mass (c − M) relation differs in normalization and shape in comparison to previous studies that have limited statistics in the upper end of the mass range. We show that the flattening of the c − M relation with redshift is naturally expressed if c is viewed as a function of the peak height parameter, ν. Unlike the c − M relation, the slope of the c − ν relation is effectively constant over the redshift range z = 0 − 2, while the amplitude varies by ∼ 30% for massive clusters. This relation is, however, not universal: Using a simulation suite covering the allowed wCDM parameter space, we show that the c − ν relation varies by about ± 20% as cosmological parameters are varied. At fixed mass, the c(M) distribution is well-fit by a Gaussian with σ c / c ≃ 0.33, independent of the radius at which the concentration is defined, the halo dynamical state, and the underlying cosmology. We compare the ΛCDM predictions with observations of halo concentrations from strong lensing, weak lensing, galaxy kinematics, and X-ray data, finding good agreement for massive clusters (M vir > 4 × 10 14 h −1 M ⊙ ), but with some disagreements at lower masses. Because of uncertainty in observational systematics and modeling of baryonic physics, the significance of these discrepancies remains unclear.

LoCuSS: weak-lensing mass calibration of galaxy clusters

“…The normalisation of our best-fit mass-concentration relation is in excellent agreement with the results of recent numerical simulations at z l = 0.23 (Table 3; Figure 5;Bhattacharya et al 2013;Diemer & Kravtsov 2014;Meneghetti et al 2014). As an aside, we note that these three recent independent theoretical studies agree both with each other and with our observational results, whilst older simulations showed considerable variation between their respective mass-concentration relations and a lower overall normalization (e.g.…”

“…We measured weak-lensing mass for individual clusters by fitting tangential shear profile with the spherical NFW model and investigated the mass-concentration relation. The best-fit mass-concentration relation is in excellent agreement with recent numerical simulations (Bhattacharya et al 2013;Diemer & Kravtsov 2014;Meneghetti et al 2014). We also measured the average mass density profile for the NFW and Einasto profiles by stacked lensing analysis, considering the point mass and the two-halo term.…”

“…Numerical simulations (e.g. Bullock et al 2001;Duffy et al 2008;Bhattacharya et al 2013;Diemer & Kravtsov 2014;Meneghetti et al 2014;Ludlow et al 2014) show that the concentration depends on both the halo mass and redshift.…”

New constraints on σ8 from a joint analysis of stacked gravitational lensing and clustering of galaxy clusters

“…For a given cosmological model, b depends on the mass and the redshift of the haloes hosting the galaxies through the peak height (Sheth & Tormen 1999;Tinker et al 2010;Bhattacharya et al 2013). Finally, the cross-correlation function is…”

“…Galaxies are biased tracers of the underlying mass distribution (Sheth & Tormen 1999;Tinker et al 2010;Bhattacharya et al 2013). This severely limits the constraining power of either galaxy clustering or stacked lensing on the matter power spectrum amplitude.…”