Molecular gas is the raw material which fuels star formation throughout the Universe.  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 international Spitzer Adaptation of the Red-sequence Cluster Survey (SpARCS) collaboration found that galaxies within these distant clusters—observed as they were when the Universe was only four billion years old—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,” said lead author Allison Noble, a postdoctoral researcher 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.” Results were recently published in The Astrophysical Journal Letters. Noble is a member of Professor Michael McDonald’s research group. McDonald, the second author on this paper, is an astronomer in MIT’s Kavli Institute and an assistant professor of physics.  

“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,” said Gillian Wilson, a professor of physics and astronomy at University of California, Riverside and the leader of the SpARCS collaboration.

See also the University of California, Riverside press release

Caption: The Tadpole Galaxy is a disrupted spiral galaxy showing streams of gas stripped by gravitational interaction with another galaxy. Molecular gas is the required ingredient to form stars in galaxies in the early universe.

Credit: Hubble Legacy Archive, ESA, NASA and Bill Snyder.