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.
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This Lens System
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Lens name
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B1608+656
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Survey
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CLASS
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Images
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4
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B1950.0 coords
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16h08m50.559s
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65°40'15.290"
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J2000.0 coords
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16h09m13.956s
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65°32'28.970"
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Lens System Structure and Labelling
Image labelling for this lens (RA increases to the left, declination increases upwards)
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Image/Lens Positions
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Image/Lens
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Relative Position
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East (mas)
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North (mas)
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A
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+0.0
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+0.0
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B
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+740
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-1960
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C
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+750
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-460
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D
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-1130
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-1240
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Image/Lens Separations
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Separation (mas)
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Component
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A
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B
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C
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D
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A
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2095.0
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879.8
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1677.6
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B
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2095.0
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1500.0
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2003.8
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C
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879.8
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1500.0
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2035.4
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D
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1677.6
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2003.8
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2035.4
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Position angle (°)
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Component
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A
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B
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C
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D
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A
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-20.7
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-58.5
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42.3
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B
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159.3
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-179.6
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111.1
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C
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121.5
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0.4
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67.5
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D
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-137.7
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-68.9
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-112.5
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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.
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Radio Flux Densities
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Component
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Flux density (mJy)
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1.4 GHz
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8.4 GHz
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8.4 GHz
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18.5 GHz
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99 GHz
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A
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35.6
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34.3
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B
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17.8
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16.8
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C
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15.2
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17.4
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D
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4.6
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5.9
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Total
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84±5
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38±4
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Flux errors
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5%
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Resolution (mas)
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Map noise level
(mJy/beam)
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0.1
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0.44
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Instrument
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WSRT
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VLA
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VLA
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OVRO
40 metre
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OVRO
mm-array
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Date observed
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1994/10/01
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1994/03/01
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Monitoring
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1994/10
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1994/10/4
1994/10/5
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Reference
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[2]
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[1]
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[4]
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[2]
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[2]
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Sub-millimetre Flux Densities
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Component
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Flux density (mJy)
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3000 μm
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1300 μm
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850 μm
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Total
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8.1±0.4
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5.6±1.7
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8.1±1.7
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Estimated
cal. error
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5-10%
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Instrument
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PdBI (IRAM)
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SCUBA (JCMT)
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SCUBA (JCMT)
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Date observed
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1999-2001
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Reference
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[6]
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[6]
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[6]
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Optical Imaging
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Component
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Brightness (Magnitudes)
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r
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i
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r
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r-i
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K
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Ks
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Source
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20.2
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0.6
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Lens
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20.0
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0.7
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Galaxy
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0.06mJy/arcsec^2
in 1.1" disc
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Total
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19.4
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19.2
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Instrument
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COSMIC
(Palomar 5 m)
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COSMIC
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Palomar 1.5m
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NIRC (Keck)
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Integration time
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5ex, 3600 sec
in total
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450sec
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25exp @ 40sec
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PSF size (arcsec)
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1.5
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1.5
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1.4
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1
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0.7
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Pixel scale (mas/pixel)
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372
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125
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Date observed
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1994/08/09
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1994/08/09
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1995/04
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1994/08/22
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1995/07/18
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Reference no.
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[1]
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[1]
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[3]
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[3]
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[1]
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[3]
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Redshifts
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Object
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Redshift
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Instrument
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Date Observed
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Reference
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Lens galaxy
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0.6304
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Palomar 5m
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1994/08/09
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[1]
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Source
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1.394
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Palomar 5m
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1995/07
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[3]
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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.
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Notes
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.
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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.
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[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)
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[2] Radio Observations of the Quadruple Lens 1608+656, I. A. G. Snellen et al., Astrophys. J. Let. 447, p. L9 (1995)
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[3] 1608+656: A Gravitationally Lensed Post-starburst Radio Galaxy, C. D. Fassnacht et al., Astrophys. J. Let. 460, pp. L103 (1996)
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[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)
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[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)
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[6] A submillimeter survey of gravitationally lensed quasars, R. Barvainis and R. Ivison, Astrophys. J. 571, pp. 712-720 (2002)
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