Galaxy orbits and the intracluster gas temperature in clusters

Abstract

In this paper, we examine how well galaxies and intracluster gas trace the gravitational potential of clusters. Utilizing mass profiles derived from gravitational lensing and X-ray observations, coupled with measured galaxy velocities, we solve for the velocity anisotropy parameter β_(orb)(r) using the anisotropic Jeans equation. This is done for five clusters, three at low redshift: A2199, A496 and A576 and two at high redshifts: A2390 and MS1358. We use X-ray temperature profiles obtained from Chandra and ASCA/ROSAT data to estimate β_X(r), the ratio of energy in the galaxies compared to the X-ray gas. We find that none of these clusters is strictly in hydrostatic equilibrium. We compare the properties of our sample with clusters that form in high-resolution cosmological N-body simulations that include baryonic physics. Simulations and data show considerable scatter in their β_(orb)(r) and β_X(r) profiles. We demonstrate the future feasibility and potential for directly comparing the orbital structure of clusters inferred from multiwavelength observations with high-resolution simulated clusters.