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CLASS B1608+656, a quad image gravitational lens



Lens System Summary

B1608+656 is a quad image lens. Monitoring with the VLA has produced a time delay measurement for this system, from which Fassnacht et al. (1999) and Koopmans & Fassnacht obtain an estimate for H0 of 59+8-7 km s-1 Mpc-1 (2σ). There appear to be two lens galaxies.

This Lens System

Lens name B1608+656
Survey CLASS
Images 4
B1950.0 coords 16h08m50.559s 65°40'15.290"
J2000.0 coords 16h09m13.956s 65°32'28.970"

Lens System Structure and Labelling

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

Elements labelled as in S. T. Myers et al.

Image/Lens Positions

Image/Lens Relative Position
East (mas) North (mas)
A +0.0 +0.0
B +740 -1960
C +750 -460
D -1130 -1240

Image/Lens Separations

Separation (mas)
Component A B C D
A
2095.0 879.8 1677.6
B 2095.0
1500.0 2003.8
C 879.8 1500.0
2035.4
D 1677.6 2003.8 2035.4
Position angle (°)
Component A B C D
A
-20.7 -58.5 42.3
B 159.3
-179.6 111.1
C 121.5 0.4
67.5
D -137.7 -68.9 -112.5

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.

Optical and IR images Click to see a larger version
WFPC2 I-band image
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WFPC2 V-band image
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Combined HST I/V image
Radio maps Click to see a larger version
MERLIN 5GHz image
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MERLIN 5GHz image
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VLA 8.4GHz image

Radio Flux Densities

Component Flux density (mJy)
1.4 GHz 8.4 GHz 8.4 GHz 18.5 GHz 99 GHz
A
35.6 34.3

B
17.8 16.8

C
15.2 17.4

D
4.6 5.9

Total


84±5 38±4
Flux errors
5%


Resolution (mas)




Map noise level
(mJy/beam)
0.1 0.44


Instrument WSRT VLA VLA OVRO
40 metre
OVRO
mm-array
Date observed 1994/10/01 1994/03/01 Monitoring 1994/10 1994/10/4
1994/10/5
Reference [2] [1] [4] [2] [2]

Sub-millimetre Flux Densities

Component Flux density (mJy)
3000 μm 1300 μm 850 μm
Total 8.1±0.4 5.6±1.7 8.1±1.7
Estimated
cal. error


5-10%
Instrument PdBI (IRAM) SCUBA (JCMT) SCUBA (JCMT)
Date observed

1999-2001
Reference [6] [6] [6]

Optical Imaging

Component Brightness (Magnitudes)
r i r r-i K Ks
Source

20.2 0.6

Lens

20.0 0.7

Galaxy



0.06mJy/arcsec^2
in 1.1" disc

Total 19.4 19.2



Instrument COSMIC
(Palomar 5 m)
COSMIC
Palomar 1.5m NIRC (Keck)
Integration time

5ex, 3600 sec
in total

450sec 25exp @ 40sec
PSF size (arcsec) 1.5 1.5 1.4
1 0.7
Pixel scale (mas/pixel)

372

125
Date observed 1994/08/09 1994/08/09 1995/04
1994/08/22 1995/07/18
Reference no. [1] [1] [3] [3] [1] [3]

Redshifts

Object Redshift Instrument Date Observed Reference
Lens galaxy 0.6304 Palomar 5m 1994/08/09 [1]
Source 1.394 Palomar 5m 1995/07 [3]

Lens Models

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


[5]
Detailed modelling of this system discussed. Authors examine isothermal and non-isothermal mass profiles for the system, and use the measurement of the time delay discussed in Fassnacht et al. (1999) to estimate H0.

Notes

  1. Time delay measurements undertaken using the VLA (Fassnacht et al.) combined with a mass model (Koopmans & Fassnacht) produce H0 = 59+8-7 km s-1 Mpc-1 (2 sigma). Authors estimate possible +-15km s-1 Mpc-1 systematic uncertainty.

References

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] 1608+656: A Quadruple-Lens System Found in the CLASS Gravitational Lens Survey, S. T. Myers et al., Astrophys. J. Let. 447, pp. L5 (1995)


[2] Radio Observations of the Quadruple Lens 1608+656, I. A. G. Snellen et al., Astrophys. J. Let. 447, p. L9 (1995)


[3] 1608+656: A Gravitationally Lensed Post-starburst Radio Galaxy, C. D. Fassnacht et al., Astrophys. J. Let. 460, pp. L103 (1996)


[4] A Determination of H0 with the CLASS Gravitational Lens B1608+656 (I. Time Delay Measurements with the VLA), C. D. Fassnacht et al., Astrophys. J. 527, Issue 2, pp. 498-512 (1999)


[5] A Determination of H0 with the CLASS Gravitational Lens B1608+656 (II. Mass Models and the Hubble Constant from Lensing), L. V. E. Koopmans & C. D. Fassnacht, Astrophys. J. 527, Issue 2, pp. 513-524. (1999)


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

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