Speaker
Description
Despite many studies, superclusters, the largest structures in the cosmic web containing galaxy clusters on scales of tens to hundreds of megaparsecs (Mpc), remain enigmatic in their evolutionary processes. To shed light on this, we present a catalogue of 662 superclusters identified using a modified Friends-of-Friends algorithm applied to the WHL cluster catalogue within a redshift range of $0.05 \le z \le 0.42$. Among these, the most massive supercluster at $z \sim 0.25$ is named the Einasto Supercluster. On average, superclusters exhibit a median mass of $\sim 5.8 \times 10^{15}$ M$_{\odot}$ and a median size of $\sim 65$ Mpc. While the supercluster environment affects cluster growth, comparisons with mock superclusters from the Horizon Run 4 cosmological simulation yield broad agreement. We establish a correlation between a supercluster's density contrast and its maximum extent, characterized by a $\alpha \sim -2$ power law index. Additionally, our analysis shows that, on average, $\sim 90%$ of a supercluster influences its constituent parts, as evidenced by the phase-space distribution of mock halos in and around superclusters.
Furthermore, we investigate the presence and influence of Giant Radio Galaxies (GRGs)—enormous structures powered by supermassive black holes—within supercluster environments. Leveraging the catalogues of superclusters (401) and GRGs (1446), we identify 77 GRGs (5.3%) within 64 superclusters (16%) across the redshift range $\rm 0.05 \leq z \leq 0.42$. Notably, about 70% of these GRGs are located within galaxy clusters. In contrast, among GRGs outside superclusters (comprising 94.7% of the sample), only 21% are associated with galaxy clusters, with the majority situated in sparser environments. We examine how different environments—cluster versus non-cluster and supercluster versus non-supercluster—affect GRG size and growth patterns. Our findings indicate that the largest GRGs ($\gtrsim$,3 Mpc) tend to grow in underdense regions. Furthermore, approximately 24% of the 1446 GRGs reside in galaxy clusters. GRGs appear to preferentially grow in sparser regions of the cosmic web, exhibiting significantly larger median sizes. Lastly, we highlight the utility of GRGs as astrophysical probes, particularly in estimating magnetic field strengths of supercluster environments using cases where GRGs with polarized emissions are located behind superclusters, acting as natural Faraday screens, to achieve sub-micro Gauss level estimations.
These findings present a valuable opportunity for comparison with the eROSITA data on superclusters and active galactic nuclei (AGNs) that can be crucial in our understanding of how the largest structures of the cosmic web affect the largest galaxies of the radio Universe, powered by AGNs.
