Collisions of galaxy clusters: simulating shocks and gas sloshing

 

Rubens Machado (IAG/USP)

 

Galaxy clusters often exhibit X-ray morphologies suggestive of recent interaction with an infalling subcluster. The collision of two clusters often gives rise to disturbances in the intracluster gas (such as shocks, cold fronts, gas sloshing), and these can be studied through numerical simulations. I will discuss the modelling of two observed clusters by means of dedicated hydrodynamical simulations that aim at reconstructing their dynamical histories. The first example, Abell 3376, is a nearby 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 970 kpc away from the peak of X-ray emission. The second one, Abell 2052, is a moderately rich cluster that exhibits a spiral-shaped region of cold gas, a few hundred kpc across. This feature is seen as an excess in X-ray brightness and is interpreted as a sloshing cold front, due to a non-frontal collision in the past. We attempt to propose specific scenarios for each of these merging events. Our simulations also allow us to explore details of the supersonic shock waves and of the dark matter distributions.