Cosmology dependence of galaxy cluster scaling relations

Abstract

The abundance of galaxy clusters as a function of mass and redshift is a well known powerful cosmological probe, which relies on underlying modelling assumptions on the mass-observable relations (MOR). MOR parameters have to be simultaneously fit together with the parameters describing the cosmological model. Some of the MOR parameters can be constrained directly from multi-wavelength observations, as the normalization at some reference cosmology, the mass-slope, the redshift evolution and the intrinsic scatter. However, the cosmology dependence of MORs cannot be tested with multi-wavelength observations alone. We use Magneticum simulations to explore the cosmology dependence of galaxy cluster scaling relations. We run fifteen different hydro-dynamical cosmological simulations varying Ω m , Ω b , h 0 and σ 8 (around a reference cosmological model). The MORs considered in this work are gas mass, gas temperature, Y and velocity dispersion as a function of the spherical overdensity virial mass. We verify that the mass and redshift slopes and the intrinsic scatter of the MORs are nearly independent of cosmology with variations significantly smaller than current observational uncertainties. We show that the gas mass sensitively depends only on the baryon fraction, velocity dispersion and gas temperature sensitively depend on the hubble constant, and Y depends on both baryon fraction and the hubble constant. We investigate the cosmological implications of our MOR parameterization on a mock catalog created for an idealized eROSITA-like experiment. We show that our parametrization introduces a strong degeneracy between the cosmological parameters and the normalization of the MOR, degeneracy that can be broken by combining multiple observables and hence improve the cosmological parameter constraints. Finally, the parameter constraints derived at different overdensity (∆ 500c ), for X-ray bolometric gas luminosity and stellar mass, and for different subgrid physics prescriptions are shown in the appendix.

Cosmology dependence of halo masses and concentrations in hydrodynamic simulations

“…Magneticum simulations are performed with an extended version of the N−body/SPH code P-Gadget3, which is the successor of the code P-Gadget2 (Springel et al 2005b;Springel 2005;Boylan-Kolchin et al 2009), with a space-filling curve aware neighbour search (Ragagnin et al 2016), an improved Smoothed Particle Hydrodynamics (SPH) solver (Beck et al 2016); treatment of radiative cooling, heating, ultraviolet (UV) background, star formation and stellar feedback processes as in Springel et al (2005a) connected to a detailed chemical evolution and enrichment model as in Tornatore et al (2007), which follows 11 chemical elements (H, He, C, N, O, Ne, Mg, Si, S, Ca, Fe) with the aid of CLOUDY photo-ionisation code (Ferland et al 1998). Fabjan et al (2010); Hirschmann et al Singh et al (2019). Columns show, respectively: simulation name, cosmological parameters Ω , Ω , 8 , and ℎ 0 , the number of haloes selected from all redshift snapshots ( = 0.00, 0.14, 0.29, 0.47, 0.67, and = 0.9) of a given simulation and the number of haloes of that simulations at redshift = 0.…”

“…This cut is different for each of our simulations. This is opposed to what was used in Singh et al (2019), where they choose a fixed mass cut for all C1-C15 simulations. The mass range of these haloes is between 10 14 − 4 × 10 15 , which 1 In particular, Magneticum simulations match observations of angular momentum for different morphologies (Teklu et al 2015(Teklu et al , 2016; the mass-size relation (Remus & Dolag 2016; Remus et al 2017; van de Sande et al 2019); the dark matter fraction (see Figure 3 in Remus et al 2017); the baryon conversion efficiency (see Figure 10 in Steinborn et al 2015); kinematical observations of early-type galaxies (Schulze et al 2018); the inner slope of the total matter density profile (see fits the typical range of galaxy cluster weak-lensing masses (see e.g.…”

“…Error associated with fit parameters are evaluated as follows in Singh et al (2019): (1) we first re-performed the fit for each simulation by setting its own cosmological parameter as pivot values; (2) then for each parameter except 0 , 0 , 0 , we considered the standard deviation of the parameter values in the previous fits and set it as uncertainty in Table 2; (3) parameters 0 , 0 , 0 are presented without uncertainty because the error obtained from the Hessian matrix is negligible compared to the scatter parameter . Being this work first necessary step towards a cosmology-dependent mass-concentration relation, these parameters may be constrained with more precision in future simulation campaigns.…”

“…Given the weak dependency of mass from the concentration (at least in the mass range of interests of cluster of galaxies), we provide a cosmology-redshift-mass-concentration fit where, in Eq. 5 we parametrise the dependency of the cosmology only in the normalisation and in the redshift dependency as the following: Table B1 show the results of this fit, with the same procedure as in Section 4, where pivot values are the ones for the reference cosmology C8 and errors are assigned by performing the same fit as in Singh et al (2019). Table B2 show the results of the mass-concentration plane where we fit the NFW profile of the dark matter density profile 2.610 9 /ℎ and 2.610 10 /ℎ respectively, as presented in .…”

Cosmological constraints from gas mass fractions of massive, relaxed galaxy clusters

“…For massive clusters of galaxies, whose internal dynamics are dominated by gravity, the mass of the intracluster medium (ICM) correlates tightly with total mass (Borgani & Kravtsov 2011, and refer-2014Barnes et al 2017;Henden et al 2020;Singh et al 2020). Precise measurements of 5 gas from X-ray data thus provide a route to constraining cosmological models, and, in combination with external information on b , have provided some of the earliest and most robust constraints on the cosmic matter density, m (White et al 1993;David et al 1995;White & Fabian 1995;Evrard 1997;Ettori & Fabian 1999;Mohr et al 1999;Allen et al 2002;Ettori et al 2003).…”