# A Line-Of-Sight Galaxy Cluster Collision: Simulated X-Ray Observations - Astrophysics

Abstract: Several lines of evidence have suggested that the the galaxy clusterCl~0024+17, an apparently relaxed system, is actually a collision of twoclusters, the interaction occurring along our line of sight. In this paper wepresent a high-resolution $N$-body-hydrodynamics simulation of such acollision. We have created mock X-ray observations of our simulated systemusing MARX, a program that simulates the on-orbit performance of the ChandraX-ray Observatory. We analyze these simulated data to generate radial profilesof the surface brightness and temperature. At later times, $t = 2.0-3.0$ Gyrafter the collision, the simulated surface brightness profiles are better fitby a superposition of two $\beta$-model profiles than a single profile, inagreement with the observations of Cl~0024+17. In general, due to projectioneffects, much of the post-collision density and temperature structure of theclusters is not seen in the observations. In particular, the observedtemperatures from spectral fitting are much lower than the temperature of thehottest gas. We determine from our fitted profiles that if the system ismodeled as a single cluster, the hydrostatic mass estimate is a factor$\sim$2-3 less than the actual mass, but if the system is modeled as two galaxyclusters in superposition, a hydrostatic mass estimation can be made which isaccurate to within $\sim$10%. We examine some implications of these results forgalaxy cluster X-ray surveys.

Author: J. A. Zuhone, P. M. Ricker, D. Q. Lamb, H.-Y. Yang

Source: https://arxiv.org/