1. 15/6/2006 ESO (Santiago) Gravitational lensing J. Surdej Institut d’Astrophysique et de Géophysique, ULg

2. 15/6/2006ESO (Santiago) 1. Preamble 2. Historical background 3. The optical GL experiment 4. Some observations 5. Other types of mirages Layout :

3. 15/6/2006ESO (Santiago) PREAMBLE: Schematic view of the N-S arm of the Very Large Array (VLA) in Socorro (New Mexico), in the A configuration. The second last antenna, at an approximate dis- tance of 10 km, is not resolved with the naked eye (January 1988).

4. 15/6/2006ESO (Santiago) PREAMBLE: Due to atmospheric lensing, the second last antenna was doubly imaged and, while it was unresolved with the naked eye, it appeared brighter than the third and fourth last antennas.

5. 15/6/2006ESO (Santiago) PREAMBLE Atmospheric lensing: Atmospheric lensing: (g-h) correspond to two different views of the north-south arm of the Very Large Array at the National Radio Astronomical Observatory (Socorro, New Mexico) as seen in the early morning of 17 January 1989. (g) (h)

6. 15/6/2006ESO (Santiago) HISTORICAL BACKGROUND: "Do not Bodies act upon Light at a distance, "Do not Bodies act upon Light at a distance, and by their action bend its Rays; and is not and by their action bend its Rays; and is not this action strongest at the least distance?" this action strongest at the least distance?" Isaac Newton, 1704 Isaac Newton, 1704 J. Soldner (1804): 0.875” J. Soldner (1804): 0.875” XVIIIth and XIXth centuries XVIIIth and XIXth centuries

7. 15/6/2006ESO (Santiago) HISTORICAL BACKGROUND: Einstein (1911, 1915):  = 4GM  / (c 2 R  ) = 1.75", Einstein (1911, 1915):  = 4GM  / (c 2 R  ) = 1.75", Dyson et al. (1920): 20-30% uncertainty; Fomalont and Sramek (1975a, b), Robertson et al. (1991): Dyson et al. (1920): 20-30% uncertainty; Fomalont and Sramek (1975a, b), Robertson et al. (1991): << 1% uncertainty << 1% uncertainty Eddington (1920) … Eddington (1920) … see Einstein (1911) see Einstein (1911) Sir Oliver Lodge Sir Oliver Lodge (1919) (1919) A point mass object consists of a very imper- fect, although a- chromatic, lens!

8. 15/6/2006ESO (Santiago) HISTORICAL BACKGROUND: Einstein (1936) Einstein (1936) Zwicky (1937a, b) '... the probability that galactic nebulae which act as gravitational lenses will be found becomes practically a certainty.’ Zwicky (1937a, b) '... the probability that galactic nebulae which act as gravitational lenses will be found becomes practically a certainty.’

9. 15/6/2006ESO (Santiago) HISTORICAL BACKGROUND: Zwicky (1957) Zwicky (1957) Walsh, Carswell and Weymann (1979): 0957+561 Walsh, Carswell and Weymann (1979): 0957+561  4000 scientific publications (non exhaustive bibliography availa-ble on the web at the URL:  4000 scientific publications (non exhaustive bibliography availa-ble on the web at the URL: http://vela.astro.ulg.ac.be/grav_lens/) http://vela.astro.ulg.ac.be/grav_lens/)http://vela.astro.ulg.ac.be/grav_lens/ An observer sees the lensed images of a distant quasar along the directions of light rays deflected by a massive intervening galaxy.

10. 15/6/2006ESO (Santiago) THE OPTICAL GL EXPERIMENT: Deflection of a light ray passing through an axially symmetric optical lens. n = sin(i)/sin(r) ~ i / r i = r +  (  ) = r + 4GM(  )/ c 2  d  = -r d  d  = -4GM(  ) d  (n-1) c 2   (  ) =  (  0 ) + 4GM ln(  /  0 ) (n-1) c 2

11. 15/6/2006ESO (Santiago) THE OPTICAL GL EXPERIMENT: Right: examples of (upper left) a 'point mass' lens (28 cm in diameter) and of (lower right) a 'spiral galaxy' optical lens (30 cm in diameter). Below: several examples of axially symmetric optical lenses simulating the light deflection properties due to a point mass (a), a SIS galaxy (b), a spiral galaxy (c), a uniform disk (d) and a truncated uniform disk of matter (e).

12. 15/6/2006ESO (Santiago) The optical GL experiment

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16. 15/6/2006ESO (Santiago) (a-g) (h-n) (o-u)

17. 15/6/2006ESO (Santiago) OBSERVATIONS

18. 15/6/2006ESO (Santiago) RXS J11331-1231 RXS J11331-1231 (Sluse et al. 2003, 2005, Claeskens et al. 2006) : z s =0.658, z l =0.295

19. 15/6/2006ESO (Santiago) Quasar-quasar associations Burbidge et al. (1997) Sluse et al. (2003)

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23. 15/6/2006ESO (Santiago) OTHER TYPES OF MIRAGES

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