2003ApJ...592..755R

We report deep, Keck narrowband Lyα images of the luminous z>3 radio galaxies 4C 41.17, 4C 60.07, and B2 0902+34. The images show giant, 100-200 kpc scale, emission-line nebulae, centered on these galaxies, that exhibit a wealth of morphological structure, including extended low surface brightness emission in the outer regions, radially directed filaments, cone-shaped structures and (indirect) evidence for extended Lyα absorption. We discuss these features within a general scenario in which the nebular gas cools gravitationally in large cold dark matter halos, forming stars and multiple stellar systems. Merging of these ``building blocks'' triggers large-scale starbursts, forming the stellar bulges of massive radio galaxy hosts, and feeds supermassive black holes, which produce the powerful radio jets and lobes. The radio sources, starburst superwinds, and radiation pressure from active galactic nucleus then disrupt the accretion process, limiting galaxy and black hole growth, and imprint the observed filamentary and cone-shaped structures of the Lyα nebulae.