Intergalactic 'wind' strips cluster galaxies of star-forming gas

A team of astronomers have provided the first direct evidence that an intergalactic "wind" is stripping galaxies of star-forming gas as they fall into clusters of galaxies.

The observations by astronomers from the University of Toronto and the University of Arizona help explain why galaxies found in clusters are known to have relatively little gas and less star formation when compared to non-cluster or "field" galaxies.

Astronomers have theorized that as a field galaxy falls into a cluster of galaxies, it encounters the cloud of hot gas at the centre of the cluster and as the galaxy moves through this intra-cluster medium at thousands of kilometres per second, the cloud acts like a wind, blowing away the gas within the galaxy without disturbing its stars, which is known as ram-pressure stripping.

Researcher Suresh Sivanandam said that they found that the molecular hydrogen gas is also blown from the in-falling galaxy, much like smoke blown from a candle being carried into a room.

George Rieke of the University of Arizona said that cutting off the gas that forms stars is a key step in the evolution of galaxies from the early Universe to the present.

Marcia Rieke added that astronomers have assumed that something stopped the star formation in these galaxies, but it is very satisfying to see the actual cause.

The results are published in the Astrophysical Journal.