Journal Article

Simulating the Bullet Cluster

Chiara Mastropietro and Andreas Burkert

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 389, issue 2, pages 967-988
Published in print September 2008 | ISSN: 0035-8711
Published online September 2008 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2008.13626.x
Simulating the Bullet Cluster

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We present high resolution N-body/smoothed particle hydrodynamics (SPH) simulations of the interacting cluster 1E0657-56. The main and the subcluster are modelled using extended cuspy Λcold dark matter (ΛCDM) dark matter haloes and isothermal β-profiles for the collisional component. The hot gas is initially in hydrostatic equilibrium inside the global potential of the clusters. We investigate the X-ray morphology and derive the most likely impact parameters, mass ratios and initial relative velocities. We find that the observed displacement between the X-ray peaks and the associated mass distribution, the morphology of the bow shock, the surface brightness and projected temperature profiles across the shock discontinuity can be well reproduced by offset 6:1 encounters where the subcluster has initial velocity (in the rest frame of the main cluster) 2.3 times the virial velocity of the main cluster dark matter halo. A model with the same mass ratio and lower velocity (1.5 times the main cluster virial velocity) matches quite well most of the observations. However, it does not reproduce the relative surface brightness between the bullet and the main cluster. Dynamical friction strongly affects the kinematics of the subcluster so that the low-velocity bullet is actually bound to the main system at the end of the simulation. We find that a relatively high concentration (c= 6) of the main cluster dark matter halo is necessary in order to prevent the disruption of the associated X-ray peak. For a selected subsample of runs we perform a detailed three-dimensional analysis following the past, present and future evolution of the interacting systems. In particular, we investigate the kinematics of the gas and dark matter components as well as the changes in the density profiles and the motion of the system in the LXT diagram.

Keywords: methods: N-body simulations; galaxies: clusters: individual: 1E0657-56; dark matter; X-rays: galaxies: clusters

Journal Article.  14950 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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