New insights into the early universe’s galaxy clusters

MIT News Office, MIT Kavli Institute for Astrophysics and Space Research Tuesday, July 25, 2017

Molecular gas is the raw material which fuels star formation throughout the universe. Now, using the revolutionary Atacama Large Millimeter Array (ALMA) telescope, an international team of scientists has conducted one of the largest studies of molecular gas in distant galaxy clusters — rare conglomerations containing hundreds of galaxies, trillions of stars, and dark matter.  

Scientists from the Spitzer Adaptation of the Red-sequence Cluster Survey (SpARCS) collaboration observed the galaxies within these distant clusters as they were when the universe was only 4 billion years old. They found that they harbor larger molecular gas reservoirs compared to galaxies in found in more typical isolated environments with fewer galaxy neighbors, known as field galaxies.

“We expected to find molecular gas deficiencies in these cluster galaxies compared to the field,” says lead author Allison Noble, a postdoc at the MIT Kavli Institute for Astrophysics and Space Research. “Galaxies in nearby clusters are dead, lacking star formation activity and with little to no molecular gas. In these distant clusters, we are instead detecting gas-rich galaxies, but their star formation rates are on par with field galaxies.” 

The results were recently published in The Astrophysical Journal Letters. Noble is a member of the research group of Kavli Institute astronomer and assistant professor of physics Michael McDonald, who is the second author on the paper.  

Gillian Wilson, a professor of physics and astronomy at the University of California at Riverside and the leader of the SpARCS collaboration, says that while the current study "does not answer the question of which physical process is primarily responsible for causing the higher amounts of molecular gas, it provides the most accurate measurement yet of how much molecular gas exists in galaxies in clusters in the early universe.”