Scientists have observed 574 previously unknown massive galaxies using the VISTA Telescope. The objects are the first giant galaxies that formed in the universe, between 1 and 1.5 billion years after the Big Bang.
The galaxies have a mass of at least 50 billion times that of the Sun, which is comparable to our Milky Way. Moreover, the scientists found twice as many of these galactic giants than expected, which contradicts our current model of galaxy formation. Larger galaxies, they therefore reason, must have been able to form in the early universe much more quickly than believed.
"We uncovered 574 new massive galaxies – the largest sample of such hidden galaxies in the early universe ever assembled," explained Karina Caputi, lead author of the study, in a statement. "Studying them allows us to answer a simple but important question: when did the first massive galaxies appear?"
Astronomers think that the seeds of the first stars and galaxies began to form around 150 million years after the Big Bang, with structures in the universe forming in a bottom-up hierarchy. Small things were created first, and these then merged to form larger objects. The process is slow, however, and giant galaxies are assumed to take billions of years to form. But with such an abundance of massive galaxies present in the early universe, this study suggests that may not be the case.
The exact details of how galaxies first form and acquire mass are still mysterious, and solving this mystery is one of the science goals of the VISTA survey. The telescope is being used to survey the entire southern sky, and it is slowly creating a census of all distant galaxies.
"We found no evidence of these massive galaxies earlier than around one billion years after the Big Bang, so we’re confident that this is when the first massive galaxies must have formed," added Henry Joy McCracken, a co-author on the paper.
Based on the number of objects observed by the team, the vast majority of the giant galaxies observed in the universe today already existed 10 billion years ago. These objects are going receive follow-up observation from current and proposed telescopes, which will hopefully provide more clues on how these massive galaxies formed.
The paper is published in the Astrophysical Journal.