The Effect of Cooling on the Density Profile of Hot Gas in Clusters of Galaxies Is Addition.pdfVIP

POPe-755, UTAP-286, RESCEU-16/98 The Eect of Co oling on the Density Pro le of Hot Gas in Clusters of Galaxies: Is Additional Physics Needed? 1 ;2 ;3 4 Tatsushi Suginohara and Jeremiah P. Ostriker Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 ABSTRA CT We use high-resolution hydro dynamic simulations to investigate the density pro le of hot gas in clusters of galaxies, adopting a variant of cold dark matter cosmologies and employing a cosmological N-b o dy/smo othed particle hydro dynamics co de to follow the evolution of dark matter and gas. In addition to gravitational interactions, gas pressure, and sho ck heating, we include bremsstrahlung co oling in the computation. Dynamical time, two-b o dy relaxation time, and co oling time in the simulations are examined to demonstrate that the results are free from arti cial relaxation eects and that the time step is short enough to accurately follow the evolution of the system. In the simulation with nominal resolution of 66 h 1 kp c the computed cluster app ears normal, but in a higher (by a factor 2) resolution run, co oling is so ecient that the nal gas density pro le shows a steep rise toward the cluster center that is not observed 45 1 in real clusters. Also, the X-ray luminosity of 7  10 ergs s far exceeds that for any cluster of the computed temp erature. The most reasonable explanation for this discrepancy is that there are some physical pro cesses st