CLASS Survey Gravitational Lenses |
 | Minimum credit line: Image courtesy of NRAO/AUI
and the CLASS collaboration(for details, see .
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These radio maps, obtained with the VLA, show 21 gravitational lenses
discovered as part of CLASS (Cosmic Lens All-Sky Survey) plus a rediscovery
of a previously known lens system. A gravitational lens is formed when
a galaxy lies close to the line of sight to a more distant object - in
these cases, a radio-loud quasar. The action of the galaxy's gravitational
field bends the light from the distant object, forming multiple images
of it. To find the systems pictured here, 16503 radio sources were examined
with the VLA. Followup observations using radio (MERLIN and VLBA)
telescopes and the Hubble Space Telescope in the optical were then used
to confirm the systems as gravitational lenses. Systems normally have
two images (e.g. 0218+357) or four images (e.g. 0712+472 where two images
are blended and the fourth image is not quite visible in this discovery
image). A few more exotic cases are also detected (e.g. six images in
1359+154). Each image is 3.2 arcseconds on a side, except for 2108+213
which is twice as big. Investigator(s): CLASS collaboration (University of Manchester, JBO; U. Pennsylvania; NRAO; Caltech; NFRA Dwingeloo; Leiden) This image is available in the following downloadable versions:
- 534 x 768
- 1018 x 1463
- 2037 x 2927
If you would like to obtain a higher resolution version of this image,
please contact .
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Telescope
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VLA
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Date of Observation
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1999-08-16
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Type of Observation
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Continuum Observations
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Band
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X
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Wavelength
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3.6 cm
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Frequency
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8.4 GHz
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Center of Image
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RA: 24:00:0.00, Dec: 00:00:0.00 (J2000)
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Field of View
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0.0009 x 0.0009 degrees
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Technical Caption
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These images are the 22 gravitational lenses found from 30-second
A-configuration snapshots at 8.4 GHz of 16503 flat-spectrum
radio sources. The intrinsically simple, quasi-pointlike structure of
such sources allows easy detection of multiple-image gravitational lensing
and also allows it to be distinguished from intrinsic structure such as
small jets by subsequent observations at higher resolution. These images
have a resolution of 220mas and were used to search for lens systems in
the splitting range 0.3-15 arcseconds. (Bandwidth smearing prevents
reliable searches beyond about 20-30 arcsec).
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