Unveiling galaxy pair alignment in cosmic filaments: A 3D exploration using EAGLE simulation

Abstract

We investigate how galaxy pairs are oriented in three dimensions within cosmic filaments using data from the EAGLE simulation. We identify filament spines using DisPerSE and isolate galaxies residing in filamentary environments. Employing a FoF algorithm, we delineate individual filaments and determine their axes by diagonalizing the moment of inertia tensor. The orientations of galaxy pairs relative to the axis of their host filament are analyzed. Our study covers diverse subsets of filaments identified through varying linking lengths, examining how galaxy pairs align with the filament axis across different spatial parameters such as pair separation and distance from the filament spine. We observe a nearly uniform probability distribution for the cosine of the orientation angle, which is nearly identical in each case. We also investigate the effects of redshift space distortions and confirm that the probability distributions remain uniform in both real space and redshift space. To validate our approach, we conduct Monte Carlo simulations using various theoretical probability distributions. Our analysis does not reveal any evidence of preferential alignment of galaxy pairs within cosmic filaments in hydrodynamical simulations.