The Halo Effect: Unraveling Galaxy Evolution in Overdense Regions at the Cosmic Noon

• Sofia GALLEGO (UPCité, APC)

Room: 200/0-Auditorium - Auditorium P. Lehmann Galaxies are embedded within a network of interconnected filaments, essential for their formation and growth. Simultaneously, they emit radiation and enriched matter back into their environment, influencing the evolution of cosmic gas. Recent advancements in wide-field spectrographs offer a unique perspective, allowing us to probe the spatial distribution and properties of the circumgalactic medium at high redshift, particularly the Lyman-alpha line emitted by cold hydrogen gas. These insights are especially valuable in overdense regions, like protoclusters and groups, where we can explore most of the physical mechanisms at play. I will present a multi-wavelength analysis of a protocluster at the cosmic noon, which provides a unique opportunity to investigate the evolution of galaxies at a cosmic epoch of enhanced star formation and where environmental effects are most significant. Leveraging extensive data spanning the near-infrared to the ultraviolet, we uncover a densely sampled group of extended halos that exhibit complex morphological and kinematical features in Lyman-alpha, CIV, and HeII and are connected with a variety of galaxies such as interacting galaxies, mergers, and a remarkably high local density of AGN activity. These observations suggest ongoing feedback processes between AGNs and the surrounding gas, as well as an intricate formation process of the circum-galactic gas within the context of large-scale structures. These findings highlight the need for state-of-the-art theoretical interpretations of the interaction between galaxies and their surrounding gas up to intergalactic scales, as well as serving as a precursor to future large surveys targeting a statistical sample of galaxies that will revolutionize our understanding of galaxy evolution in the cosmic landscape.