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Analysis of a New Gravitational Lens FLS 1718+59

Analysis of a New Gravitational Lens FLS 1718+59. Yoon Chan Taak Feb 14 2013 Survey Science Group Workshop 2013. What is Gravitational Lensing ?. Deflection of light by body of mass Deflection angle greater for GR (factor of 2) vs (r: source-lens distance)

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Analysis of a New Gravitational Lens FLS 1718+59

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  1. Analysis of a New Gravitational Lens FLS 1718+59 Yoon Chan Taak Feb 14 2013 Survey Science Group Workshop 2013

  2. What is Gravitational Lensing? • Deflection of light by body of mass • Deflection angle greater for GR (factor of 2) • vs (r: source-lens distance) • e.g. Solar eclipse of May 1919 • Causes distortion of images

  3. Images of GL Abell 1689 cluster

  4. Images of GL Einstein Ring – SDSS J073728.45+321618.5 Einstein Cross – QSO 2237+030

  5. Images of GL

  6. Types of GL • Strong GL • Big distortions, e.g. rings, arcs, multiple img • Lens is galaxy or cluster • Weak GL • Shear distortion • Lens is galaxy or cluster, but further away from source • Microlensing • Brightness variations • Lens has stellar masses (e.g. planets)

  7. Why GL? • Requires only mass • Allows detection of dark matter • Acts as “cosmic telescope” • Lets us see more distant objects • Determines cosmological parameters • Deflection depends on redshift-distance formula • Time delay related to Hubble constant • Constrains geometry of universe

  8. Gravitational Lensing Theory • Point-mass lens • Finite lens

  9. Point Mass (Schwarzschild) Lens • Lens (Ray-trace) equation • 11 • 1 αDLS (DS/DL)b θSDS θS : lens-source angular distance α : deflection angle of light ray θ1,2: lens-img angular distances b : lens-deflection pt angular dist. α0 : Einstein rad. [(4GM/c2) (DLS/DLDS)]1/2

  10. Finite Lens • Ray-trace eqn is for 2-D plane • Change scalars to vectors for 3-D • Integrate deflection angle for all infinitesimal masses • I • Calculate numerical solution

  11. gravlens: Software for G-Lensing • Developed by C. Keeton (Rutgers) • Useful for various g-lens images • Able to find best set of lens parameters for multiple images (lensmodel) • Contains 20+ lens models • Can be superposed, diverse potentials possible

  12. FLS 1718+59 • G-lensing image in Spitzer First Look Survey Field • zlens = 0.08 • zsource = 0.245 • Closest source so far(?) • RA = 17h 18m 17.6s • Dec = 59d 31m 46s

  13. FLS 1718+59

  14. Procedures • Simulated lensing images with several setsof input variables • Mass scale of lens • X coord. of source • Ellipticity (angle) of source • Ellipticity (angle) of lens* • Assumed no external shear * Obtained from original HST image

  15. Softened Power Law Ellipsoid • s : size of flat core • s = 0 : singular isothermal ellipsoid • s ≠ 0 : nonsingular isothermal ellipsoid

  16. Results

  17. Discussion • Many sets of variables may yield similar images • A more careful approach is necessary for constraining errors • requires analysis with more sets of variables • Mgal ~1010.75Mʘ, σ ~ 150km/s • Possibly an edge-on spiral

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