Subsample of the Lyα halos detected around z≈6 quasars. The image shows how diverse is the distribution of cool hydrogen around massive galaxies at the cosmic dawn.

3D distribution of the Lyα emission around the quasar P308-21 at z≈6.23. The gas appears to be in a relatively quiescent motion, suggesting that it is moving within the dark matter halo where the central quasar resides.

Evolution of the median Lyα surface brightness profile around quasars at different redshifts. The surface brightness is corrected for redshift dimming and the projected distance is normalized by the virial radius of a 10^12.5M_☉ dark matter halo.

3D visualization of the Lyα (blue) and [CII] (orange) emission around the quasar P308-21. For more details see our ESO press release. Credit: ESO/Farina et al.; ALMA (ESO/NAOJ/NRAO), Decarli et al.; L. Calçada