| Abstract : | Galaxy clusters are the giants of hierarchical structure formation scenario in the universe. A cluster merger event is highly energetic, releasing upto 10^65 erg of binding energy. This vigorous interaction drives shocks into the intra-cluster medium (ICM), accelerating particles to relativistic velocities within cluster sized magnetic fields. Additionally, regions of magneto-hydrodynamic turbulence scatter these particles resulting in synchrotron emission observable in radio wavelengths. The ICM comprises of a hot (10^7 K) plasma which shines brightly in X-ray wavelengths. Hence, a disturbed X-ray morphology is also a signature of interaction.
Most studies on merging clusters interpret a dynamical scenario around such signatures; rather than a systematic search for interacting clusters a-priori. As the interaction timescale is a few Gyr, tracking evolution of each system is impossible. A catalog of multiple simultaneous mergers in various phases would be insightful to deduce evolution pattern of clusters. We aim to create a search algorithm to identify interacting galaxy clusters with their merging phases from optical galaxy data. Typically, a mock cluster catalog is used to tune the parameters of cluster-finding algorithm. In contrast, we formulate a parameter optimization process based on redshift-independent SZ observations. This accurately captures physical information about clusters without any cosmological presumptions. We formulate physically motivated interaction criteria for clusters in different merger phases.
We present 465 interacting candidates in merging or premerging/postmerging phases. This unique categorization is helpful to interpret evolution of dynamical states of clusters. Additionally, a few cases of interaction with radio and X-ray evidence are presented. We report a new candidate relic lying on the verge of observation sensitivity of LoTSS, an interesting outcome of the different approach of this study. The locations of interacting candidates may possibly host fainter radio structures like radio filaments and ridges which may be observed with even sensitive surveys in future.
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