“With galaxies we can look back over the last few billion years of cosmic history, the quasars take us back about 10 billion years, and finally the Lyman-alpha galaxies allow us to look back to when the universe was less than 2 billion years old.” Studies of the Cosmic Microwave Background then reach even further back, to the infant Universe, just 380 000 years after the Big Bang. “Quasars provide a unique sample that allows us to bridge the redshift gap between galaxies and the Lyman-alpha forest at the highest redshifts,” says Jiamin Hou, a junior MPE researcher who led the quasar clustering analyses within eBOSS. Finally, to map the Universe eleven billion years in the past and more, they used quasars, which are bright galaxies lit up by material falling onto a central supermassive black hole. Farther out, they used younger, blue galaxies. To create the part of the map dating back six billion years, the team used large, red galaxies. Within the eBOSS team, individual groups focused on different aspects of the analysis with each of these samples requiring careful analysis in order to remove contaminants, and to reveal the patterns of the Universe. At the heart of the new results are detailed measurements of more than two million galaxies and quasars covering 11 billion years of cosmic time. The new results come from the extended Baryon Oscillation Spectroscopic Survey (eBOSS), an international collaboration of more than 100 astrophysicists including researchers at the Max Planck Institute for Extraterrestrial Physics (MPE) that is one of the SDSS’s component surveys. Credit: Anand Raichoor (EPFL), Ashley Ross (Ohio State University) and SDSS.
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