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Cosmology and Galaxy Evolution with the SKA

Credit: NASA/JPL-Caltech/VLA/MPIA

The Southern Pinwheel galaxy, M83, imaged in ultraviolet light (blue and green) and radio emissions at a wavelength of 21 cm (red). The blue and pink pinwheel in the centre is the main stellar disk of the galaxy, and the red extended arms are composed of the neutral hydrogen gas that fuels star formation. Credit: NASA/JPL-Caltech/VLA/MPIA

By Martin Meyer & Chris Blake

The SKA will provide new insights into how galaxies are assembled over time, from the hydrogen gas that fills the universe to the properties of dark matter and dark energy that dominate the large-scale structure of the cosmos.

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

To understand the origin and nature of our universe, astronomers study the large-scale distribution of matter and energy and the evolution of this structure over cosmic time. This effort combines cosmology, which aims to understand the large-scale properties of the universe as a whole, and galaxy evolution, which studies how the universe evolved from a relatively smooth and featureless gas into the highly clustered and rich distribution of matter seen in galaxies today.

Galaxies are composed of gas, dust, stars and dark matter, and are subject to many different physical processes. Therefore, understanding galaxy evolution requires diagnostic information from across the electromagnetic spectrum.

Traditionally, studies of galaxy evolution have been based on light from optical and nearby wavelengths, such as infrared and ultraviolet light. However, such observations are blind to one of the most ubiquitous materials in the universe: neutral atomic hydrogen.

Hydrogen dominated the early gas content of the universe, and provides the main fuel for all stars and galaxies. Neutral hydrogen can be observed only via an atomic energy transition that emits a photon with a radio wavelength close to 21 cm. With a lifetime of around 11 million years, this transition is extremely rare for any given atom. However, it can be detected by radio astronomers because there...

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