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Adaptive Optics
Newsletter
Volume 2
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ASTRONOMERS OBSERVE DISTANT GALAXIES MORE CLEARLY Using the unprecedented power of adaptive optics combined with the 10-meter (400 inch) Keck II telescope, UCLA astronomers and Center for Adaptive Optics (CfAO membersTiffany Glassman and Dr. James Larkin are peering into the distant universe to discover what our own Milky Way galaxy might have been like at the time our sun was forming. The observations are an important step forward in the process of understanding how galaxies formed and how they evolved into the wide variety seen today. "For the first time, we're able to get very detailed images in a survey of distant galaxies in the infrared," said Larkin, associate professor of astronomy at UCLA speaking at the annual meeting of the American Astronomical Society. "These new measurements will help pin down the details of galaxy evolution, and they show that adaptive optics will play an important role in understanding galaxy formation billions of years ago." The ten galaxies observed are about 5 billion light years from earth (redshift of about 0.5), a period when the universe was about two-thirds of its present age. This time span represents a significant portion of the lifetime of a galaxy and is far enough back to begin to discriminate between different theories of galaxy formation. "This is an important first step in gaining much more information about galaxies in the early universe," said Glassman, graduate student in astronomy at UCLA. "Though our current sample is small and the results preliminary, our only clue towards an understanding of how galaxies - like our own Milky Way - form is to look further and further into the past, and adaptive optics promises to be one of the best ways to do that." Galaxies are among the largest cohesive structures in the universe, often consisting of more than 100 billion stars. At great distances, however, even these vast structures appear as only small smudges through the world's largest ground-based telescopes. Adaptive optics (AO) allows astronomers to remove much of the blurring effects of the earth's atmosphere and achieve sharper images than any previously taken. These sharper images allow the sizes of galaxies, as well as the properties of smaller components that make up each galaxy, to be studied. Glassman and Larkin observed galaxies whose dominant components are a large, flattened disk and a central, spherical bulge, similar to the Milky Way and other nearby spiral galaxies. With AO the same basic properties (size and brightness of the disks and bulges) can be measured for the distant galaxies they observed and for local galaxies. The astronomers can now compare these properties to see how the galaxies have changed over billions of years. They found that as a group the disks of the distant galaxies are 2.5 times brighter at their center and 20% smaller than local disks. A less quantitative analysis of the galaxies' bulges showed that their central brightness also fades by about a factor of 2 but their size stays relatively constant. The results produced by Glassman and Larkin support other observations and theories that indicate that large galaxies were primarily assembled more than 10 billion years ago and are slowly fading as a group as the rate of new star formation declines. To continue their research, Glassman and Larkin are building a much larger sample of galaxies including many at significantly greater distances. This survey is possible because of a new camera for the Keck Telescope's Adaptive Optics system called NIRC2 (Near Infrared Camera 2) which has been available to the researchers since July through the cooperation of the camera team led by Keith Matthews of Caltech. NIRC2 has a much larger field of view and is significantly more sensitive than the earlier cameras and greatly improves the quality of the data available to Glassman and Larkin. "This new sample should allow for more detailed comparisons between local and distant galaxies, but perhaps more importantly it will contain a small number of galaxies seen just after their initial formation," said Glassman. "Detailed images like these, of galaxies in their infancy, will give astronomers the best handle on how galaxies first assembled."
 
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