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Abstract
Italy Large dust reservoirs (up to approximately 108M&Odot;) have been detected13 in galaxies out to redshift z ≃ 8, when the age of the Universe was only about 600 Myr. Generating substantial amounts of dust within such a short timescale has proven challenging for theories of dust formation4,5 and has prompted the revision ofthe modelling of potential sites of dust production6-8, such asthe atmospheres of asymptotic giant branch stars in low-metallicity environments, supernova ejecta and the accelerated growth ofgrains in the interstellar medium. However, degeneracies between different evolutionary pathways remain when the total dust mass of galaxies is the only available observable. Here we report observations of the 2,175 Å dust attenuation feature, which is well known in the Milky Way and galaxies at z ≃ 3 (refs. 9-11), in the near-infrared spectra of galaxies up to z ≃ 7, correspondingto the first billion years of cosmic time. The relatively short timescale implied forthe formation of carbonaceous grainsgiving rise to this feature12 suggests a rapid production process, possibly in Wolf-Rayet stars or supernova
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1 Willmer 1Kavli Institute for Cosmology, University of Cambridge, Cambridge, UK. Cavendish Laboratory, University of Cambridge, Cambridge, UK
2 Steward Observatory, University of Arizona, Tucson, AZ, USA
3 Astrophysics Research Institute, Liverpool John Moores University, Liverpool, UK
4 Willmer 1Kavli Institute for Cosmology, University of Cambridge, Cambridge, UK. Cavendish Laboratory, University of Cambridge, Cambridge, UK. Department of Physics and Astronomy, University College London, London, UK
5 Scuola Normale Superiore, Pisa, Italy