Inside an early star-forming galaxy
U.S. astronomers from the California Institute of Technology (Caltech) have used adaptive optics (AO) on the 10-meter Keck Telescope in Hawaii in conjunction with other images provided by the Hubble Space Telescope to look inside a young star-forming galaxy as it appeared only two billion years after the Big Bang. The team made their observations by coupling two techniques, gravitational lensing and laser-assisted guide star (LGS) adaptive optics. 'Adaptive optics corrects the blurring effects of Earth's atmosphere by real-time monitoring of the signal from a natural guide star or an artificial guide star.' But read more...
You can see above "an image of J2135-0102, a z ~ 3.07 galaxy magnified 28 ± 3 times into a near-complete Einstein ring. This image combines a Hubble Space Telescope V606 image (blue) with near-infrared images from the Keck Laser Guide Star Adaptive Optics system in [O III] 5,007 Å (green) and broadband K (red). The foreground lensing galaxy at z ~ 0.7 is the resolved red source at the centre of the image. The large extent of the ring compared with the image-plane resolution of our observations (0.13 arcsec) enables us to map the variation in spectral and dynamical properties of the background galaxy in fine detail." (Credit: Caltech) Here is a link to a larger version.
This other illustration describes how adaptative optics work. "The deformable mirror, wavefront sensor and control system perform real-time corrections to the atmospheric distortions." (Credit: Stark/Ellis with Caltech Digital Media Center) You'll find a larger version of this slide on this page at Caltech.
Here is a comment from Richard Ellis, Professor of Astronomy at Caltech. "For decades, astronomers were content to build bigger telescopes, arguing that light-gathering power was the primary measure of a telescope's ability. However, adaptive optics and interferometry are now providing ground-based astronomers with the additional gain of angular resolution. The combination of a large aperture and exquisite resolution is very effective for studying the internal properties of distant and faint sources seen as they were when the universe was young. This is the exciting future we can expect with TMT [short for Thirty Meter Telescope] and ALMA [short for Atacama Large Millimeter Array], and, thanks to the magnification of a gravitational lens, we have an early demonstration here in this study."
This research work has been published in Nature under the title "The formation and assembly of a typical star-forming galaxies at redshift z~3" (Volume 455, Number 7214, Pages 775-777, October 9, 2008). Here is the editor's summary, Inside a young galaxy. "Much of what we know about galaxies comes from observations of those that are cosmologically close to us. It is much harder to find out what is going on in the remote star-forming regions of the Universe, where faintness and small angular size mean that only the overall properties of a galaxy are normally observable. But adaptive optics is beginning to bring the interiors of young galaxies, at redshifts equivalent to two to three billion years after the Big Bang, into the observable range. Now by combining adaptive optics with gravitational lensing, where light from a distant galaxy is magnified by the pull of a massive object on the way to Earth, Stark et al. have observed J21352–0102, a typical star-forming galaxy down to a linear resolution of about 100 parsecs. They find a well-ordered compact source in which molecular gas is being converted efficiently into stars, likely to result in a spheroidal bulge similar to those seen in spiral galaxies at the present day."
Here are two additional links to the abstract and to figures and tables accompanying the article. The top illustration in this post comes from this article.
Sources: California Institute of Technology news release, October 8, 2008; and various websites
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