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JVAS B2114+022, a double image gravitational lens

Lens System Summary

B2114+022 was discovered in the JVAS survey, although difficulties in confirming it as a lens system held back publication of its discovery. As argued in Augusto et al. and Chae, Mao and Augusto, the system is an example of multi-plane lensing, where two galaxies at different redshifts lens the background source. The nearer lens (G1) is a post-starburst (E+A) galaxy, while the more distant galaxy (G2) appears to be an elliptical. Components A and D are regarded as the multiple images of the background source, while B and C are considered to be emission connected with G1.

This Lens System

Lens name B2114+022
Survey JVAS
Images 2
B1950.0 coords 21h14m18.745s 02°13'11.040"
J2000.0 coords 21h16m50.740s 02°25'46.270"

Lens System Structure and Labelling

Image labelling for this lens (RA increases to the left, declination increases upwards)

Images labelled as in P. Augusto et al.

Image/Lens Positions

Image/Lens Relative Position
East (mas) North (mas)
A 0.0 0.0
B 175±1 333±1
C 397±1 43±1
D 2286±1 1158±2
G1 555±10 40±10
G2 700±10 1336±10

Image/Lens Separations

Separation (mas)
Component A B C D G1 G2
376.2 399.3 2562.6 556.4 1508.3
B 376.2
365.2 2266.5 479.8 1132.1
C 399.3 365.2
2193.5 158.0 1328.0
D 2562.6 2266.5 2193.5
2060.7 1596.0
G1 556.4 479.8 158.0 2060.7
G2 1508.3 1132.1 1328.0 1596.0 1304.1
Position angle (°)
Component A B C D G1 G2
-152.3 -96.2 -116.9 -94.1 -152.3
B 27.7
-37.4 -111.3 -52.4 -152.4
C 83.8 142.6
-120.6 -88.9 -166.8
D 63.1 68.7 59.4
57.1 96.4
G1 85.9 127.6 91.1 -122.9
G2 27.7 27.6 13.2 -83.6 6.4

Maps and Images

Click on an image to see a larger JPEG version, or click on the accompanying text to download a gzipped FITS or PostScript file of the map or image. The images and maps are available in one gzipped file here. To see a DSS image of the region around this lens, click here - note that you will have to start the search manually by clicking on the 'Search' button.

Survey images Click to see a larger version
Image from WCS
Optical, IR and combined images Click to see a larger version
NIRC K-band image of G1 and G2
Augusto et al.
Click to see a larger version
Superimposed H-band NICMOS and 5GHz MERLIN data
Augusto et al.
Radio Images Click to see a larger version
MERLIN 5GHz image (30 mas)
Augusto et al.
Click to see a larger version
MERLIN 5GHz image (50 mas)
Augusto et al.
Click to see a larger version
VLA 15GHz image
Augusto et al.
Optical Spectra Click to see a larger version
LRIS spectrum of G1
Augusto et al.
Click to see a larger version
LRIS spectrum of G2
Augusto et al.
Click to see a larger version
Radio spectra of lensed images
Augusto et al.

Radio Flux Densities

Component Flux density (mJy)
1.6 GHz 1.6 GHz 5 GHz 5 GHz 5 GHz 8.4 GHz 15 GHz
A 73.2±2 45 44 66.0±2 65 38.0±1 18.8±1
B 32.6±2 28 37 53.4±2 52 36.2±1 18.5±1
C 13.0±1 20
16.1±1 16 13.1±1 6.4±1
D 29.6±1 26 16 20.4±1 21 12.5±1 7.1±1
Flux errors

Resolution (mas) 180 20 3 50 50 200 110
Map noise level


Date observed 1993/09/27 1997/05/31 1995/11/12 1995/06/02
1995/06/02 1992/10/18
Reference [2] [2] [2] [2] [2] [2] [2]

Sub-millimetre Flux Densities

Component Flux density (mJy)
850 μm
Total <4.3
cal. error
Instrument SCUBA (JCMT)
Date observed 1999-2001
Reference [4]

Optical Imaging

Component Brightness (Magnitudes)
K V (555nm) I (814nm) H (F160W)
20.6±0.1 19.0±0.1 17.0±0.1
21.9±0.1 19.5±0.1 17.3±0.1
Radio Images

>25 >23
Instrument NIRC (Keck) WFPC2 (HST) WFPC2 (HST) NICMOS (HST)
Integration time 20 min 1000 sec 3000 sec 5250 sec
PSF size (arcsec) 0.8 0.05 0.05 0.13
Pixel scale (mas/pixel)
50 50 130
Date observed 1996/07/31 1997/07/03 1997/07/03 1997/08/28
Reference no. [2] [2] [2] [2]


Object Redshift Instrument Date Observed Reference
G1 0.3157±0.0003 LRIS (Keck II) 1997/07/26 [2]
G2 0.5883±0.0003 LRIS (Keck II) 1997/07/26 [2]

Lens Models

Click on the model's reference number to go to the relevant paper's abstract on ADS.

Augusto et al. use two models; SIS (G1) + external shear (G2), and a single SIE (G1). Neither are satisfactory. Both have zero D.O.F. Both suggest that any external shear is not solely due to G2.

Chae, Mao and Augusto undertake extensive modelling of this lens system, treating it as a case of multiple-plane lensing.


  1. Multi-plane lens?

  2. No evidence for variability above 10% level over several years.

  3. Astrometry obtained using NOT CCD image and Carlsberg Automatic Meridian Circle measurements. Estimated NICMOS H/MERLIN 5GHz data registration error is 0.1 arcsec.

  4. Component D coincides with single bad NICMOS pixel, as identified in NICMOS images of other lenses.

  5. Components A and D have similar surface brightnesses. B and C have similar surface brightnesses (different from A and D). A and D appear <10mas in size, while B and C are extended on >10mas scales.

  6. G1 classified as a starburst (E+A) galaxy. G2 is an elliptical galaxy.

  7. No sign of optical or IR emission from components A to D down to I = 25 and H = 23. D is separated from G1 by 2 arcsec, so absorption of emission from D by G1 considered unlikely.


Click here to see the CASTLES data available for this object, or here to search for references on NED. You can go to a paper's abstract on ADS by clicking its reference number.

[1] Gravitationally lensed radio sources in the Jodrell Bank-VLA Astrometric Survey, L. J. King et al., Mon. Not. R. Astron. Soc. 307, pp. 225-235 (1999)

[2] B2114+022: a distant radio source gravitationally lensed by a starburst galaxy, P. Augusto et al., Mon. Not. R. Astron. Soc. 326, p. 1007 (2001)

[3] Modelling the first probable two-plane lens system B2114+022: reproducing two compact radio cores A and D, K.H Chae, S. Mao and P. Augusto, Mon. Not. R. Astron. Soc 326, p. 1015 (2001)

[4] A submillimeter survey of gravitationally lensed quasars, R. Barvainis and R. Ivison, Astrophys. J. 571, pp. 712-720 (2002)

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