Researchers discover large galaxies strip star-making gas from nearby smaller galaxies

Astronomers published new research this week, discovering that small satellite galaxies contain less molecular gas in their centers. The team says that large galaxies are known to strip away gas occupying the space between the stars of smaller satellite galaxies. They now know that the larger galaxies can strip away molecular gas at the center of the smaller galaxies, which is the type of gas the smaller galaxies that need to create new stars.

The lead author of the new research is Dr. Adam Stevens, an astrophysicist from UW who works for the International Center for Radio Astronomy Research. Stevens says the study provides scientists with new systemic evidence that small galaxies everywhere lose some molecular gas when they get close to a larger galaxy and the larger hot gas halo surrounding that massive galaxy. The continued acquisition of gas is how galaxies grow and can form new stars.

Without a supply of gas, galaxies stagnate. While researchers have known for a long time that large galaxies can strip atomic gas from the outskirts of the small galaxies, this is the first time they've been able to test with molecular gas in the same detail. Galaxies don't typically live alone. They usually have other galaxies around them. When a galaxy moves through the hot intergalactic medium or a larger galaxy halo, some cold gas in that galaxy is stripped away.

Scientists say this is a fast-acting process known as ram pressure stripping. The research involved a global collaboration of scientists with team members hailing from the University of Maryland, Max Planck Institute for Astronomy, University of Heidelberg, Harvard-Smithsonian Center for Astrophysics, University of Bologna, and Massachusetts Institute of Technology. The team notes that molecular gas is very difficult to detect directly.

For the study, the team used a state-of-the-art cosmological simulation. It made direct predictions for the amount of atomic and molecular gas that should be observed by specific surveys via the Arecibo telescope in Puerto Rico and the IRAM 30-meter telescope in Spain. Actual observations were then taken from the telescopes and compared to the original predictions. The team says they were very close.