Euclid Quick Data Release (Q1)

The matter around galaxy clusters is distributed over several filaments, reflecting their positions as nodes in the large-scale cosmic web. The number of filaments connected to a cluster, i.e. its connectivity, is expected to affect the physical properties of clusters. Using the first Euclid galaxy catalogue from the Euclid Quick Release 1 (Q1), we investigated the connectivity of galaxy clusters and how it correlates with their physical and galaxy member properties. Around 220 clusters located within the three fields of Q1 (covering ∼63 deg2) were analysed in the redshift range 0.2 < z < 0.7. Due to the photometric redshift uncertainty, we reconstructed the cosmic web skeleton, and measured the cluster connectivity, in 2D projected slices with a thickness of 170 comoving h−1 Mpc and centred on each cluster redshift, by using two different filament finder algorithms on the most massive galaxies (M★ > 1010.3 M⊙). In agreement with previous measurements, we recovered the mass-connectivity relation independently of the filament detection algorithm, showing that the most massive clusters are, on average, connected to a larger number of cosmic filaments, consistent with hierarchical structure formation models. Furthermore, we explored the possible correlations between connectivities and two cluster properties: the fraction of early-type galaxies and the Sérsic index of galaxy members. Our result suggests that the clusters populated by early-type galaxies exhibit higher connectivity compared to clusters dominated by late-type galaxies. These preliminary investigations highlight our ability to quantify the impact of the cosmic web’s connectivity on cluster properties with Euclid.