We report on the analysis of a suite of SPH simulations ( incorporating cooling and star formation ) of mergers involving idealised X-ray clusters whose initial conditions resemble relaxed clusters with cool compact cores observed by Chandra and XMM .
The simulations sample the most interesting , theoretically plausible , range of impact parameters and progenitor mass ratios .
We find that all mergers evolve via a common progression .
We illustrate this progression in the projected gas density , X-ray surface brightness , SZ , temperature , and gas entropy maps .
Several different classes of transient “ cold front ” -like features can arise over the course of a merger .
Each class is distinguished by a distinct morphological signature and physical cause .
We find that all of these classes are present in Chandra and XMM observations of merging systems and propose a naming scheme for these features : “ comet-like ” tails , bridges , plumes , streams and edges .
In none of the cases considered do the initial cool compact cores of the primary and the secondary get destroyed during the course of the mergers .
Instead , the two remnant cores eventually combine to form a new core that , depending on the final mass of the remnant , can have a greater cooling efficiency than either of its progenitors .
We quantify the evolving morphology of our mergers using centroid variance , power ratios and offset between the X-ray and the projected mass maps .
We find that the centroid variance best captures the dynamical state of the cluster .
It also provides an excellent indicator of how far the system is from virial and hydrostatic equilibrium .
Placing the system at z = 0.1 , we find that all easily identified observable traces of the secondary disappear from a simulated 50 \mbox { ks } Chandra image following the second pericentric passage .
The system , however , takes an additional \sim 2 Gyr to relax and virialize .
Observationally , the only reliable indicator of a system in this state is the smoothness of its the X-ray surface brightness isophotes , not temperature fluctuations .
Temperature fluctuations at the level of \Delta T / T \sim 20 \% , can persist in the final systems well past the point of virialization , suggesting that that the existence of temperature fluctuations , in and of themselves , do not necessarily indicate a disturbed or unrelaxed system .