title: Galaxy evolution. Quasar quartet embedded in giant nebula reveals rare massive structure in distant universe.
abstract: All galaxies once passed through a hyperluminous quasar phase powered by accretion onto a supermassive black hole. But because these episodes are brief, quasars are rare objects typically separated by cosmological distances. In a survey for Lyman-α emission at redshift z ≈ 2, we discovered a physical association of four quasars embedded in a giant nebula. Located within a substantial overdensity of galaxies, this system is probably the progenitor of a massive galaxy cluster. The chance probability of finding a quadruple quasar is estimated to be ∼10(-7), implying a physical connection between Lyman-α nebulae and the locations of rare protoclusters. Our findings imply that the most massive structures in the distant universe have a tremendous supply (≃10(11) solar masses) of cool dense (volume density ≃ 1 cm(-3)) gas, which is in conflict with current cosmological simulations.
authors.affiliation: Max-Planck-Institut für Astronomie, Heidelberg, Germany. joe@mpia.de.
authors.forename: Joseph F
authors.initials: JF
authors.lastname: Hennawi
authors.affiliation: University of California Observatories-Lick Observatory, University of California Santa Cruz, Santa Cruz, CA, USA.
authors.forename: J Xavier
authors.initials: JX
authors.lastname: Prochaska
authors.affiliation: University of California Observatories-Lick Observatory, University of California Santa Cruz, Santa Cruz, CA, USA. ETH Zurich, Institute for Astronomy, Zurich, Switzerland.
authors.forename: Sebastiano
authors.initials: S
authors.lastname: Cantalupo
authors.affiliation: Max-Planck-Institut für Astronomie, Heidelberg, Germany.
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Arrigoni-Battaia