Alan McConnachie studies isolated dwarf galaxy found stripped of gas

A dwarf galaxy in the direction of the constellation Pegasus is being stripped of its gas, according to astronomers.

A galaxy needs its gas to create new stars. So we might be seeing this galaxy near the end of its ability to form stars.

Alan McConnachie at the University of Victoria in Canada and his colleagues studied hydrogen gas in the Pegasus dwarf galaxy. The gas is bunched up in the southeastern part of the galaxy and extended in the opposite direction. This suggests the galaxy is moving southeastward through material that is striking the galaxy’s gas and stripping it away.

The Pegasus dwarf galaxy belongs to our Local Group of galaxies – several dozen nearby galaxies, including our own Milky Way. Many other small galaxies in the Local Group have lost all their gas and no longer give birth to new stars. Most of these gas-poor galaxies orbit either our galaxy or the nearby Andromeda Galaxy. It’s thought the larger galaxies stripped the smaller ones of their gas.

But the Pegasus dwarf is isolated. It’s 3 million light-years from our Milky Way galaxy and more than a million light-years from the Andromeda Galaxy. These astronomers say their discovery is strong evidence for material existing in the space between galaxies of our Local Group.

Over time, that intergalactic medium might convert the Pegasus dwarf from a gas-rich galaxy to a gas-poor galaxy, unable to form new stars.

Our thanks to:
Alan McConnachie
University of Victoria

March 31, 2008

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