Lens System Summary
B2045+265 is a quad-image lens. There is radio emission near the centre of the lens, most likely from the lensing galaxy since its radio spectrum is different from that of the images. The mass-to-light ratio derived from the measured redshifts (zlens=0.8673; zsrc=1.28) and image splittings (1.9 arcsec) suggests that the Sa-type lensing galaxy has a signicantly higher dark matter content than expected from others of that type.
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This Lens System
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Lens name
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B2045+265
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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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20h45m11.587s
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26°32'57.760"
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J2000.0 coords
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20h47m20.290s
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26°44'02.700"
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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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-134±1
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-248±1
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C
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-288±1
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-789±1
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D
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+1628±6
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-1007±6
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E
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1121±5
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-824±5
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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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E
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A
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281.9
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839.9
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1914.3
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1391.3
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B
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281.9
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562.5
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1918.5
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1380.9
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C
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839.9
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562.5
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1928.4
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1409.4
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D
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1914.3
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1918.5
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1928.4
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539.0
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E
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1391.3
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1380.9
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1409.4
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539.0
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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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E
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A
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28.4
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20.1
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-58.3
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-53.7
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B
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-151.6
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15.9
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-66.7
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-65.3
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C
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-159.9
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-164.1
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-83.5
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-88.6
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D
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121.7
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113.3
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96.5
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109.8
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E
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126.3
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114.7
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91.4
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-70.2
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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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4.9 GHz
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5.0 GHz
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5.0 GHz
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8.5 GHz
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8.5 GHz
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14.9 GHz
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14.9 GHz
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A
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29.02
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23.40
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16.8
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15.8
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18.4
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16.55
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15.5
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10.69
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B
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15.73
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12.65
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9.82
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8.09
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9.42
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8.90
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9.18
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5.75
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C
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19.92
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15.19
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14.8
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8.75
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14.8
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10.99
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11.8
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7.13
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D
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2.81
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2.68
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2.02
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2.41
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1.77
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1.22
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1.05
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E
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2.18
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3.00
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1.53
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1.83
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2.34
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2.36
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1.90
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Flux errors
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Resolution (mas)
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1500
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430
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60
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2.5
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250
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250
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140
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140
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Map noise level
(mJy/beam)
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0.08
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0.06
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0.15
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0.20
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0.28
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0.01
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0.32
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0.14
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Instrument
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VLA
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VLA
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MERLIN
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VLBA
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VLA
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VLA
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VLA
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VLA
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Date observed
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1996/12/31
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1996/12/31
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1997/11/30
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1995/11/12
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1995/09/02
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1996/12/30
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1995/09/11
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1996/12/31
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Reference
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[1]
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[1]
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[1]
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[1]
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[1]
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[1]
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[1]
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[1]
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Sub-millimetre Flux Densities
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Component
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Flux density (mJy)
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850 μm
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450 μm
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Total
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<3.7
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<22
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Estimated
cal. error
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5-10%
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5-10%
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Instrument
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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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1999-2001
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Reference
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[3]
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[3]
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Optical Imaging
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Component
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Brightness (Magnitudes)
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J
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F160W
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K
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A
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20.6
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B
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21.0
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C
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20.9
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Lensing galaxy
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19.2
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18.6
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17.6
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'Arc'
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19.6
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18.7
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17.3
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Instrument
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NIRC (WHT)
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NIC1/NICMOS (HST)
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NIRC (WHT)
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Integration time
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27ex @ 1 min
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2624 sec
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45ex @ 1 min
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PSF size (arcsec)
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0.75-1.15
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0.45-0.90
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Pixel scale (mas/pixel)
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43
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Date observed
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1996/07/31
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1997/07/14
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1996/07/31
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Reference no.
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[1]
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[1]
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[1]
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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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0.8673±0.0005
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LRIS (Keck)
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1996/06/18
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[1]
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Source
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1.28±0.01
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LRIS (Keck)
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1996/06/18
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[1]
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Lens Models
Click on the model's reference number to go to the relevant paper's abstract on ADS.
[1] SIS model produces image positions, but can't reproduce flux density ratios. Fassnacht et al. recover flux density ratios using the SIS with a small positive mass perturbation located near the 'arc' of A->B->C. Model predicts time delays between A, B and C of 6.5 to 7.7 h-1 hours. Delays between any of A, B, C and component D are on the order of 142 h-1 days.
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Notes
Only limited attempts to detect variability undertaken so far - Fassnacht et al. report possible detection, but require high resolution VLA monitoring of the system to rule out other possibilities (specifically, variation in component E).
Fassnacht et al. report lens spectrum typical for an Sa galaxy. Source redshift derived from MgII line.
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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] B2045+265: A New Four-Image Gravitational Lens from CLASS, C. D. Fassnacht et al., Astron. J. 117, Issue 2, pp. 658-670 (1999)
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[2] IRAM observations of JVAS/CLASS gravitational lenses, E. Xanthopoulos, F. Combes, T. Wiklind, Mon. Not. R. Astron. Soc. 325, Iss. 1, p. 273 (2001)
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[3] A submillimeter survey of gravitationally lensed quasars, R. Barvainis and R. Ivison, Astrophys. J. 571, pp. 712-720 (2002)
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