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CLASS B2045+265, a quad image gravitational lens



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.

This Lens System

Lens name B2045+265
Survey CLASS
Images 4
B1950.0 coords 20h45m11.587s 26°32'57.760"
J2000.0 coords 20h47m20.290s 26°44'02.700"

Lens System Structure and Labelling

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

Components labelled as in C. D. Fassnacht et al.

Image/Lens Positions

Image/Lens Relative Position
East (mas) North (mas)
A +0.0 +0.0
B -134±1 -248±1
C -288±1 -789±1
D +1628±6 -1007±6
E 1121±5 -824±5

Image/Lens Separations

Separation (mas)
Component A B C D E
A
281.9 839.9 1914.3 1391.3
B 281.9
562.5 1918.5 1380.9
C 839.9 562.5
1928.4 1409.4
D 1914.3 1918.5 1928.4
539.0
E 1391.3 1380.9 1409.4 539.0
Position angle (°)
Component A B C D E
A
28.4 20.1 -58.3 -53.7
B -151.6
15.9 -66.7 -65.3
C -159.9 -164.1
-83.5 -88.6
D 121.7 113.3 96.5
109.8
E 126.3 114.7 91.4 -70.2

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
NICMOS H-band image
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NIRC K-band image
Radio Maps Click to see a larger version
MERLIN 5GHz image
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VLA 8.4GHz image
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VLA 14GHz image
Optical Spectra Click to see a larger version
Spectrum of lens
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Spectrum of source

Radio Flux Densities

Component Flux density (mJy)
1.4 GHz 4.9 GHz 5.0 GHz 5.0 GHz 8.5 GHz 8.5 GHz 14.9 GHz 14.9 GHz
A 29.02 23.40 16.8 15.8 18.4 16.55 15.5 10.69
B 15.73 12.65 9.82 8.09 9.42 8.90 9.18 5.75
C 19.92 15.19 14.8 8.75 14.8 10.99 11.8 7.13
D 2.81 2.68 2.02
2.41 1.77 1.22 1.05
E 2.18 3.00 1.53
1.83 2.34 2.36 1.90
Flux errors







Resolution (mas) 1500 430 60 2.5 250 250 140 140
Map noise level
(mJy/beam)
0.08 0.06 0.15 0.20 0.28 0.01 0.32 0.14
Instrument VLA VLA MERLIN VLBA VLA VLA VLA VLA
Date observed 1996/12/31 1996/12/31 1997/11/30 1995/11/12 1995/09/02 1996/12/30 1995/09/11 1996/12/31
Reference [1] [1] [1] [1] [1] [1] [1] [1]

Sub-millimetre Flux Densities

Component Flux density (mJy)
850 μm 450 μm
Total <3.7 <22
Estimated
cal. error
5-10% 5-10%
Instrument SCUBA (JCMT) SCUBA (JCMT)
Date observed 1999-2001 1999-2001
Reference [3] [3]

Optical Imaging

Component Brightness (Magnitudes)
J F160W K
A
20.6
B
21.0
C
20.9
Lensing galaxy 19.2 18.6 17.6
'Arc' 19.6 18.7 17.3
Instrument NIRC (WHT) NIC1/NICMOS (HST) NIRC (WHT)
Integration time 27ex @ 1 min 2624 sec 45ex @ 1 min
PSF size (arcsec) 0.75-1.15
0.45-0.90
Pixel scale (mas/pixel)
43
Date observed 1996/07/31 1997/07/14 1996/07/31
Reference no. [1] [1] [1]

Redshifts

Object Redshift Instrument Date Observed Reference
Lens galaxy 0.8673±0.0005 LRIS (Keck) 1996/06/18 [1]
Source 1.28±0.01 LRIS (Keck) 1996/06/18 [1]

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.

Notes

  1. 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).

  2. Fassnacht et al. report lens spectrum typical for an Sa galaxy. Source redshift derived from MgII line.

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] B2045+265: A New Four-Image Gravitational Lens from CLASS, C. D. Fassnacht et al., Astron. J. 117, Issue 2, pp. 658-670 (1999)


[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)


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

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