Tracing Multiphase AGN Feedback at Cosmic Dawn: ALMA–JWST Insights into z ~ 6 Quasar Outflows.

Quasars at z ~ 6 host rapidly growing supermassive black holes whose energetic output is expected to drive powerful feedback capable of influencing early galaxy evolution. Galactic outflows in these systems are predicted to span multiple gas phases, ranging from cold, neutral gas to warm, ionized gas. Their spatial extent and kinematic structure provide key insights into how feedback couples to the interstellar medium. In this work, we investigate multiphase outflows in a sample of z ~ 6 quasars observed with ALMA in [C II] and JWST/NIRSpec IFU spectroscopy, which covers the rest-optical emission lines ([O III], Hβ, Hα). The ALMA [C II] data probe the cold gas that may dominate the outflow mass, while JWST probes the ionized phase. Using the JWST IFU data, we construct flux, velocity, and velocity-dispersion maps and measure the spatial extent and morphology of ionized outflows. These measurements, combined with multicomponent spectral fitting to derive ionized gas masses, outflow rates, and energetics, are compared directly to [C II]–based estimates of the cold component. By correlating velocities, momentum fluxes, and spatial extents between phases, we test whether cold and ionized outflows are co-spatial or arise from different regions of the host galaxy, quantify the relative mass loading in each phase, and investigate trends with AGN luminosity and black hole properties. This study aims to assess whether early quasars drive momentum- or energy-dominated winds, evaluate their capacity to evacuate or heat the gas reservoir on kiloparsec scales, and provide new constraints on the strength and spatial reach of AGN feedback in the first billion years of cosmic time.