Journal or Book Title
Tracing Cosmic Evolution with Galaxy Clusters
We investigate the X-ray vs. optical scaling relations of poor groups
to small clusters ( 100−700 km/s) identified in a cosmological hydro-
dynamic simulation of a ΛCDM universe, with cooling and star forma-
tion but no pre-heating. We find that the scaling relations between X-ray
luminosity, X-ray temperature, and velocity dispersion show significant
departures from the relations predicted by simple hydrostatic equilibrium
models or simulations without cooling, having steeper LX− and LX−TX
slopes and a “break” at 200 km/s ( 0.3 keV). These departures arise
because the hot (X-ray emitting) gas fraction varies substantially with
halo mass in this regime. Our predictions roughly agree with observa-
tions. Thus radiative cooling is a critical physical process in modeling
galaxy groups, and may present an alternative to ad hoc models such as
pre-heating or entropy floors for explaining X-ray group scaling relations.
Dave, R; Katz, N; Hernquist, L; and Weinberg, D, "Group Scaling Relations From a Cosmological Hydrodynamic Simulation: No Pre-heating Required?" (2001). Tracing Cosmic Evolution with Galaxy Clusters. 985.