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Black Death

Credit: vchalup/adobe

Credit: vchalup/adobe

By Ivy Wong

A new study suggests that some galaxies suddenly stop forming stars because the gas they use for star formation is blown away by the activity of their central supermassive black holes.

The full text of this article can be purchased from Informit.

There are two types of galaxies: those that are actively forming stars, and those that are not. Galaxies that are forming stars are bluer in colour, while galaxies that no longer form stars are redder.

As a galaxy ages, it slowly runs out of the gas from which stars are formed. Eventually it will stop forming stars and start to redden as its stars begin to fade and redden.

Using results from the Sloan Digital Sky Survey and modelling the evolution of the stellar population in these galaxies, my colleagues and I have found that there are two main pathways by which galaxies stop forming stars:

  • a fast way that takes several hundred million years for star formation to stop; and
  • a slow path that takes the galaxy two billion or more years to stop forming stars.

In our current epoch, spheroidal galaxies typically display the fast track of evolution, while spiral galaxies evolve over much longer timescales. Our Milky Way is one of these middle-aged spirals that is ageing sedately and currently forming stars at the rate of just one Sun per year.

My personal interest is in the galaxies that live fast and die young. These galaxies have very strong bursts of star formation but then experience a sudden shutdown or quenching of star birth. These galaxies are called “post-starburst” galaxies.

We realised a few years...

The full text of this article can be purchased from Informit.