X-ray mass proxies from hydrodynamic simulations of galaxy clusters (paper I)
Abstract
We present a detailed study of scaling relations between total cluster mass and three mass proxies based on X-ray observables: temperature of the intra-cluster medium, gas mass and the product of the two, YX. Our analysis is based on two sets of high-resolution hydrodynamical simulations performed with the TreePM-SPH GADGET code. The first set includes about 140 clusters with masses above 5x1013 Msun/h (30 having mass above 1015 Msun/h), that have been simulated with (i) non-radiative physics and including (ii) cooling, star formation, chemical enrichment and the effect of supernova feedback triggering galactic ejecta. This large statistics is used to quantify the robustness of the scaling relations, to determine their redshift evolution and to calibrate their intrinsic scatter and its distribution. We use a smaller set of clusters including 18 halos with masses above 5x1013 Msun/h to test the robustness of mass proxies against changing the physical processes included in simulations (thermal conduction, artificial viscosity, cooling and star formation, galactic winds and AGN feedback). We find the M-YX scaling relation to be the least sensitive one to variations of the ICM physics, with its slope and redshift evolution close to the self-similar model predictions. The distribution of the scatter around the best-fitting relations is close to a log-normal one. Mgas has the smallest scatter in mass, with values of sigmalnM = 0.04-0.06, depending on the physics included in the simulation, and with a mild dependence on redshift. The M-T relation is the one with the largest scatter, with sigmalnM > 0.1 at z=0, increasing to > 0.15 at z=1. The intrinsic scatter in the M-YX relation is slightly larger than in the M-Mgas relation. These results confirm that both YX and Mgas mass proxies are well suited for cosmological applications of future large X-ray surveys. [abridged]