Simulations of the merging galaxy cluster Abell 3376

Abstract

Observed galaxy clusters often exhibit X-ray morphologies suggestive of recent interaction with an infalling subcluster. Abell 3376 is a nearby (z = 0.046) massive galaxy cluster whose bullet-shaped X-ray emission indicates that it may have undergone a recent collision. It displays a pair of Mpc-scale radio relics and its brightest cluster galaxy is located 970h −1 70 kpc away from the peak of X-ray emission, where the second brightest galaxy lies. We attempt to recover the dynamical history of Abell 3376. We perform a set of N -body adiabatic hydrodynamical simulations using the SPH code Gadget-2. These simulations of binary cluster collisions are aimed at exploring the parameter space of possible initial configurations. By attempting to match X-ray morphology, temperature, virial mass and X-ray luminosity, we set approximate constraints on some merger parameters. Our best models suggest a collision of clusters with mass ratio in the range 1/6-1/8, and having a subcluster with central gas density four times higher than that of the major cluster. Models with small impact parameter (b < 150 kpc), if any, are preferred. We estimate that Abell 3376 is observed approximately 0.5 Gyr after core passage, and that the collision axis is inclined by i ≈ 40 • with respect to the plane of the sky. The infalling subcluster drives a supersonic shock wave that propagates at almost 2600 km/s, implying a Mach number as high as M ∼ 4; but we show how it would have been underestimated as M ∼ 3 due to projection effects.

Galaxy cluster mergers as triggers for the formation of jellyfish galaxies: case study of the A901/2 system

“…The requirement of hydrostatic equilibrium determines the gas temperatures. Realisations of these initial conditions are created according to the procedures described in Machado & Lima Neto (2013). The virial masses, virial radii and gas fractions of the initial conditions are given in Table 1.…”

Physical properties of the X-ray gas as a dynamical diagnosis for galaxy clusters

“…The temperature and metallicity maps obtained by Bagchi et al (2006) show patches of hotter gas and a higher metallicity in the southeast half of the cluster. Hydrodynamical simulations by Machado & Lima Neto (2013) computed to match the Xray properties suggest a collision of two clusters with mass ratio between 1:6 and 1:8, the subcluster having a gas density four times that of the main cluster. The merger seems to correspond to a small impact parameter (< 150 kpc), with a collision axis inclined by ∼ 40 • with respect to the plane of the sky, and having taken place 0.5 Gyr ago, with a large Mach number of ∼ 4.…”

Weak lensing and spectroscopic analysis of the nearby dissociative merging galaxy cluster Abell 3376

“…Using N-body hydrodynamical simulations, Machado & Lima Neto (2013) had proposed a scenario of a post minor-merger (mass ratio around 1:6-1:8) whose pericentric passage would have happened 0.5 Gyr before the observed configuration. Due to the unavailability of lensing data at the time, those authors had considered the BCGs (∼970 kpc apart from each other) as tracers of the dark matter halo centroids.…”