Average dark matter halo sparsity relations as consistency check of mass estimates in galaxy cluster samples

Abstract

The dark matter halo sparsity provides a direct observational proxy of the halo mass profile, characterizing halos in terms of the ratio of masses within radii which enclose two different overdensities. Previous numerical simulation analyses have shown that at a given redshift the halo sparsity carries cosmological information encoded in the halo mass profile. Moreover, its ensemble averaged value can be inferred from prior knowledge of the halo mass function at the overdensities of interest. Here, we present a detailed study of the ensemble average properties of the halo sparsity. In particular, using halo catalogs from high-resolution N-body simulations, we show that its ensemble average value can be estimated from the ratio of the averages of the inverse halo masses as well as the ratio of the averages of the halo masses at the overdensity of interests. This can be relevant for galaxy clusters data analyses. As an example, we have estimated the average sparsity properties of galaxy clusters from the LoCuSS and HIFLUGCS datasets respectively. The results suggest that the expected consistency of the different average sparsity estimates can provide a test of the robustness of mass measurements in galaxy cluster samples.

Cosmology dependence of halo masses and concentrations in hydrodynamic simulations

“…This kind of conversions is used in computing the sparsity of haloes (i.e. ratio of masses in two overdensities), which itself can probe cosmological parameters (Corasaniti et al 2018;Corasaniti & Rasera 2019) and dark energy models (Balmès et al 2014).…”

Cosmological Constraints from Galaxy Cluster Sparsity, Cluster Gas Mass Fraction and Baryon Acoustic Oscillations Data

“…(2) holds valid to better than percent level (see e.g. Table 1 in Corasaniti & Rasera 2019). Hence, Eq.…”

“…The validity of Eq. (2) in predicting the ensemble average halo sparsity has been extensively tested using N-body halo catalogs from the RayGalGroupSims simulation of a ΛCDM model in Corasaniti et al (2018) and the halo catalogs from the MultiDark-Planck2 simulation in Corasaniti & Rasera (2019). These studies have shown that the simulation calibrated mass functions can predict the average halo sparsity to better then a few percent accuracy level.…”

“…The validity of Eq. (2) has been extensively tested using halo catalogs from high-resolution large volume N-body simulations in Corasaniti et al (2018); Corasaniti & Rasera (2019) and we refer the readers to these publications for further details. In particular, for the halo masses used in this work, namely M 200c and M 500c , which correspond to masses within radii enclosing the overdensity ∆ = 200 and 500 respectively (in units of the critical density ρ c ), the analysis of the N-body halo catalogs has shown that Eq.…”

“…D. AVERAGE SPARSITY CONSISTENCY RELATIONS Corasaniti & Rasera (2019) have shown that the validity of Eq. ( 2) also implies the validity of the following relations:…”