A team of astronomers using the Advanced Camera for Surveys and the Wide Field Camera onboard NASA’s Hubble Space Telescope has discovered the most distant cosmic magnifying glass yet found – a huge elliptical galaxy whose powerful gravity is magnifying the light from a faraway galaxy behind it.
Gravitational lensing by a giant elliptical galaxy in the cluster IRC 0218: the galaxy (red object in the enlarged view at left) is so massive that its gravity bends, magnifies, and distorts light from objects behind it, a phenomenon called gravitational lensing; the object behind the cosmic lens (seen in the enlarged view at right) is a small spiral galaxy undergoing a rapid burst of star formation; its light has taken 10.7 billion years to arrive here. Image credit: NASA / ESA / Kim-Vy Tran, Texas A&M University / Kenneth Wong, Academia Sinica Institute of Astronomy & Astrophysics.
In the Hubble image, the galaxy is seen as it appeared 9.6 billion years ago and is one of the brightest members in the distant galaxy cluster IRC 0218. Its red color comes from the light from older stars.
The background image shows the entire region surrounding the galaxy.
In the enlarged view, the lighter-colored blobs at upper right and lower left are the distorted and magnified shapes of a more distant spiral galaxy behind the foreground elliptical.
The giant elliptical is so massive that its enormous gravitational field deflects light passing through it, much as an optical lens bends light to form an image.
This phenomenon, called gravitational lensing, magnifies, brightens, and distorts images from faraway objects that might otherwise be too faint to observe even with the largest telescopes.
The team, led by Dr Kenneth Wong of the Institute of Astronomy and Astrophysics in Taipei, Taiwan used Hubble’s high-resolution spectroscopy to determine that the blobby features were two images of the same distant galaxy, located 10.7 billion light-years from Earth.
In the enlarged view at right, the scientists have subtracted the image of the giant red elliptical to show the more distant spiral galaxy. The glow of young stars makes the galaxy appear blue. The white area at upper right is probably a region of star formation.
“When you look more than 9 billion years ago in the early Universe, you don’t expect to find this type of galaxy-galaxy lensing at all,” said Dr Kim-Vy Tran of Texas A&M University in College Station, who is a co-author of a paper on the discovery in the Astrophysical Journal Letters (arXiv.org pre-print).
“It’s very difficult to see an alignment between two galaxies in the early Universe. Imagine holding a magnifying glass close to you and then moving it much farther away.”
“When you look through a magnifying glass held at arm’s length, the chances that you will see an enlarged object are high. But if you move the magnifying glass across the room, your chances of seeing the magnifying glass nearly perfectly aligned with another object beyond it diminishes.”
The astronomers suspect that the lensing galaxy will continue to grow over the next 9 billion years, gaining stars and dark matter by cannibalizing neighboring galaxies.
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Kenneth C. Wong et al. 2014. Discovery of a Strong Lensing Galaxy Embedded in a Cluster at z = 1.62. ApJ 789, L31; doi: 10.1088/2041-8205/789/2/L31
