The splashback radius (also known as the last density caustic or the second turnaround radius) is a sharp dark matter halo edge that corresponds to the location of the first orbital apocenter of satellite galaxies after their infall. This definition of a halo boundary is more physical compared to the traditional definitions of halo boundaries which tend to be quite arbitrary. The splashback radius responds to the mass assembly history of clusters. For dark matter halos of the same mass, a large mass accretion rate results in a smaller splashback radius, since its deeper halo potential well has a closer apocenter. Using two cluster samples which had the same mass, but different splashback radii, we set out to check if the incidences of active galactic nuclei (AGN) in the member galaxies of these clusters are affected by their mass assembly history. Using SDSS spectroscopic data, we determined metallicity of galaxies and constructed a BPT diagram to classify each galaxy member in each cluster (Seyfert, Liner, Composite, etc.) and determined if an AGN was likely to be present. We compared the samples and determined that the rapidly assembling sample did have a larger AGN presence.
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