Cosmological hydrodynamical simulations of galaxy clusters: X-ray scaling relations and their evolution

Abstract

We analyse cosmological hydrodynamical simulations of galaxy clusters to study the X-ray scaling relations between total masses and observable quantities such as X-ray luminosity, gas mass, X-ray temperature, and Y X . Three sets of simulations are performed with an improved version of the smoothed-particle-hydrodynamics GADGET-3 code. These consider the following: non-radiative gas, star formation and stellar feedback, and the addition of activegalactic-nucleus (AGN) feedback. We select clusters with M 500 > 10 14 M E(z) −1 , mimicking the typical selection of Sunyaev-Zeldovich samples. This permits to have a mass range large enough to enable robust fitting of the relations even at z ∼ 2. The results of the analysis show a general agreement with observations. The values of the slope of the mass -gas mass and mass − temperature relations at z = 2 are 10 per cent lower with respect to z = 0 due to the applied mass selection, in the former case, and to the effect of early merger in the latter. We investigate the impact of the slope variation on the study of the evolution of the normalization. We conclude that cosmological studies through scaling relations should be limited to the redshift range z = 0 − 1, where we find that the slope, the scatter, and the covariance matrix of the relations are stable. The scaling between mass and Y X is confirmed to be the most robust relation, being almost independent of the gas physics. At higher redshifts, the scaling relations are sensitive to the inclusion of AGNs which influences low-mass systems. The detailed study of these objects will be crucial to evaluate the AGN effect on the ICM.

Aging haloes: implications of the magnitude gap on conditional statistics of stellar and gas properties of massive haloes

“…The log-normal model, besides its mathematical tractability, is justified theoretically and verified through hydrodynamical simulations (e.g., Evrard et al 2008;Stanek et al 2010;Truong et al 2018;Farahi et al 2018). For example, Farahi et al (2018) illustrate that the integrated stellar mass and gas mass of halos extracted from the BAHAMAS and MACSIS hydrodynamical simulations follow a log-normal form.…”

“…This quantity is the correlation in the scatter of a pair of halo properties at fixed halo mass. The magnitude and sign of this correlation are sensitive to sub-grid models and how the baryons evolve within the potential well of the host dark matter halo (Stanek et al 2010;Wu et al 2015;Truong et al 2018;Farahi et al 2018). A precise and accurate estimation of this quantity will allow us to improve our understanding of sub-grid physics.…”

“…While slope and scatter of the mean relations may be scaledependent and/or evolve with redshift (e.g., Le Brun et al 2017;Truong et al 2018;Farahi et al 2018), at the mass scales that are considered in this work the scale-dependence is negligible. The current observational data are yet not rich enough to model these effects.…”

“…For example, in the context of modeling star formation, a log-normal shape for final stellar mass naturally emerges when random factors govern the evolution of the system (e.g., Larson 1973;Zinnecker 1984). In the past decade, observations (Pratt et al 2009;Reichert et al 2011;Mahdavi et al 2013;Lieu et al 2016;Mantz et al 2016a,b;McClintock et al 2019;Golden-Marx & Miller 2019;Mulroy et al 2019) and simulations (Evrard et al 2008;Stanek et al 2010;Truong et al 2018;Farahi et al 2018;Bradshaw et al 2019) have employed the power-law, log-normal model and extensively studied and quantified the mean and scatter of mass-observables relation. These studies found that the a powerlaw model with a log-normal scatter is a sufficient model to describe integrated properties of the most massive systems.…”

A tight correlation between the enclosed gravitational mass and hot gas mass in galaxy clusters at intermediate radii

“…However, these processes might be significant in galaxies, but not in galaxy clusters because the amount of baryons is quite insignificant (f ∼ 0.1) to affect the gravitational potential and the baryonic feedbacks in the intergalactic hot gas medium are nearly negligible. Some numerical simulations show that strong baryonic feedbacks such as AGN feedback may be able to alter the hot gas structure as well as the dark matter distribution [57,54]. However, whether dark matter could be rigorously controlled by the much smaller amount of normal matter is still controversial [58].…”