Multiphase gas reservoirs around z~3 quasars and the impact of feedback from host-galaxy to halo scales

Extended Ly-alpha nebulae observed around quasars trace the cool gas within the circumgalactic medium and can provide key insights into the complex interplay between gas dynamics and active galactic nuclei (AGN) feedback. However, the connection between this cool phase and the cold molecular gas of the host galaxies remains largely unexplored. In this talk, I leverage ALMA CO(4–3) observations of 37 quasars at z ~ 3, all of which have been previously mapped in Ly-alpha with VLT/MUSE, to investigate the relation between the CO emission, and hence the molecular gas content, and halo properties. I show that systems with higher black hole mass and lower Eddington ratio exhibit higher CO detection rates while also demonstrating lower Ly-alpha surface brightness. This result suggest that radiative feedback regulates cold gas survival in dusty, gas-rich environments and consequently influences the reprocessed Ly-alpha emission from halo gas. I report on the incidence and properties of CO-emitting companions to quantify the quasar–galaxy clustering and to investigate the impact of the quasar environment on surrounding galaxies. Additionally, I explore a connection between the orientation of the quasar host galaxy disks and the large-scale morphology and kinematics of the Ly-alpha nebulae. This investigation aims to provide a deeper understanding of the connections between quasar activity and the multiphase gas content of quasar host galaxies and their halos.