It is known that large galaxies cleanse the space inside themselves of gas that occupies the space between the stars of smaller satellite galaxies. In the new study, astronomers described that these small satellite galaxies also contain less molecular gas at their centers.

Molecular gas is found in giant clouds at the centers of galaxies and is the building block for new stars. Therefore, large galaxies steal material that their smaller counterparts need to form new stars.

This study provides new systematic evidence that small galaxies everywhere are losing some of their molecular gas as they approach the larger galaxy and the surrounding hot gas halo.

“Gas is the“ blood ”of the galaxy. As they continue to accumulate gas, galaxies grow and form stars. Without it, galaxies stagnate. We’ve known for a long time that large galaxies remove atomic gas from the outskirts of small galaxies. But until now this has not been studied in the same detail with molecular gas. “

Adam Stevens, Astrophysicist, International Center for Radio Astronomy Research (ICRAR).
Galaxies don’t usually live in isolation. When a galaxy moves through a hot intergalactic medium or galactic halo, some of the cold gas is removed. This fast acting process is known as ram pressure stripping.

This makes molecular gas very difficult to detect directly. The research team has carried out state-of-the-art cosmological simulations and made direct predictions of the amount of atomic and molecular gas to be observed through special surveys at the Arecibo telescope in Puerto Rico and the 30-meter IRAM telescope in Spain.

They then took actual observations from the telescopes and compared them to their original predictions. So the 30-meter IRAM telescope observed molecular gas in more than 500 galaxies. These are the deepest observations and the largest sample of atomic and molecular gas in the local Universe.

The team’s conclusion is consistent with previous evidence suggesting a lower star formation rate in satellite galaxies. The purified gas first enters the space around the larger galaxy. It could end up raining down on a large galaxy or just stay in its surroundings. But in most cases, a small galaxy is still doomed to merge with a larger one.

They often live for one to two billion years and then merge into the center. Thus, this affects how much gas they will have at the time of their merger, which in turn will affect the evolution of a large system. Once galaxies get large enough, they begin to rely on getting more matter from the cannibalism of smaller galaxies.