“This was the most comprehensive survey ever done covering the bulk of the galaxies that represent conditions in the early universe,” Glazebrook said. “We expected to find basically zero massive galaxies beyond about 9 billion years ago, because theoretical models predict that massive galaxies form last. Instead, we found highly developed galaxies that just shouldn’t have been there, but are.”
These findings challenge the dominant theory of galactic evolution, which posits that at this early stage, galaxies should have formed from the bottom up, with small pieces crashing together to build small and then ever larger galaxies. Called the “hierarchical model,” this scenario predicts that normal-to-large galaxies such as those studied by GDDS would not yet exist.
The GDDS team, which included Nature paper co-authors Roberto Abraham from the University of Toronto, Patrick McCarthy from the Observatories of the Carnegie Institution of Washington and David Crampton of the National Research Council of Canada’s Herzberg Institute of Astrophysics, was supported by a grant from the Packard Foundation and by institutional support from the National Science Foundation, Canada’s National Research Council, the Natural Sciences and Engineering Research Council of Canada and the United Kingdom’s Particle Physics and Research Council, among others.