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Weekly Science Update

Friday, April 24, 2009
Starburst Galaxies in the Early Universe
About eight billion years before our own sun formed, the universe underwent a period of dramatic star formation. Galaxy collisions were frequent back then, and those interactions prompted galaxies' gas clouds to collapse and form new stars at a rate about five times higher than we see today. This early burst of activity had a major impact on the cosmos, first enriching it with the chemicals essential for life, and then disbursing them as stars evolved and died. The precise conditions and reasons for the intense star formation in the early universe are not well understood, but since these events shaped our own environment, scientists are busy trying to figure out what happened, and why.

Harvard graduate student Josh Younger led a team of nine scientists, including SAO astronomers Giovanni Fazio, Jiasheng Huang, and Kamson Lai, in a study of twelve galaxies so distant that their light has been traveling toward us for about ten billion years. His research, part of his recently completed Ph.D. thesis, used millimeter wavelengths to study these galaxies; most of their energy lies in the infrared and millimeter where warm dust heated by the hyperactive bursts of star formation preferentially radiates.

The sample was discovered in deep images of the sky taken by infrared cameras onboard the Spitzer Space Telescope; these sources stood out by being very red in infrared colors. The team was able to detect nine of them in the millimeter; then, by combining the millimeter and far infrared data, the astronomers were able to estimate the luminosity, temperature, and mass of the dust in the galaxies. By comparing their new results with the properties of much closer galaxies, the scientists determined that although distant, and although star formation is more active, the physical processes at work in these objects are very similar to those in nearby analogs. The work suggests that no new kinds of mechanisms are needed to explain the burst of star-forming activity in these objects.


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