Coffee talks
Friday 09/10/2026 @ 11:30, Sala riunioni quarto piano e on-line (meet.google.com/sue-bwvk-axf)
Lwandile Gwebushe (Rhodes University, South Africa), "Neutral hydrogen in the Shapley Supercluster core – II. Gas content and star formation in the filaments connecting the core"
I will present the second HI study of the Shapley Supercluster core, focusing on the role of the environment in shaping the gas content and star formation properties of galaxies. We combine archival MeerKAT observations of the dense supercluster centre with five new MeerKAT L-band pointings targeting the filamentary structures connecting the core to the northern and southern clusters Abell 3559 and Abell 3560. These HI observations are combined with the optical and spectroscopic data from the Shapley Supercluster Survey (ShaSS), allowing us to identify supercluster members and study galaxies across different environmental densities at the same redshift. We investigate HI gas content, gas-fraction scaling relations, star-formation activity, HI depletion timescales, and optical morphology. The global HI detection fraction increases from approximately 21% in the cluster centre to 49% in the filaments. While cluster galaxies show progressively lower HI gas fractions towards the red sequence, filament galaxies can retain substantial HI reservoirs despite suppressed star formation. Approximately 78% of the HI-detected filament galaxies have HI depletion times longer than the Hubble time, indicating inefficient conversion of atomic gas into stars. These results provide evidence that environmental effects on galaxy evolution extend beyond the dense cluster environment and can already be important within the surrounding large-scale structure.