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Observing gravitationally lensed AGN

Observing gravitationally lensed AGN. Marc-André Besel. Motivation. Outline. Valuable tool since last 30 years for: Probing cosmography and dark matter Determine mean stellar masses in lensing galaxies Observing quasars. History Theoretical aspects An Example Unveiling quasar hosts

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Observing gravitationally lensed AGN

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  1. Observing gravitationally lensed AGN Marc-André Besel

  2. Motivation Outline Valuable tool since last 30 years for: • Probing cosmography and dark matter • Determine mean stellar masses in lensing galaxies • Observing quasars • History • Theoretical aspects • An Example • Unveiling quasar hosts • Probing quasar structure with microlensing Active Galactic Nuclei (ASTR597G) The University of Arizona

  3. History • 1804 Soldner calculated deflection by sun using Newtonian gravity • 1915 Einstein redireved light deflection using full field equations • 1919 First measurement during ToSE • 1937 Zwicky: Gravitational lensing could split light of background images and magnifies distant sources. • 1964 Refsdal had the idea to measure H0 by GL • 1979 Walsh et al. discover first lensed quasar Q0957+561 at the MMT6”.26, zs=1.41 • 1980 first quadruply imaged quasar PG1115+080 using the MMT Structures and Dynamics of Galaxies (ASTR540) - The University of Arizona

  4. What do we need? (Astro 101) • Source • Mass (as lens) • Observer Structures and Dynamics of Galaxies (ASTR540) - The University of Arizona

  5. More advanced – deflection angle Structures and Dynamics of Galaxies (ASTR540) - The University of Arizona

  6. Deflection angle Apply Fermat’s principle Introduce arbitary curvature Apply Lagrangian formalism, using , we get: Lagrangian Structures and Dynamics of Galaxies (ASTR540) - The University of Arizona

  7. Deflection angle Assume the tangent vector to be normalized Gradient of n perpendicular to the light path Deflection angle is now the integral over –e along the light path Structures and Dynamics of Galaxies (ASTR540) - The University of Arizona

  8. Deflection Angle • Deflection angle is integral over the ‘pull’ of the gravitational potential perpendicular to the light path Structures and Dynamics of Galaxies (ASTR540) - The University of Arizona

  9. Deflection angle • Point mass Arbitrary thin screen mass distribution Structures and Dynamics of Galaxies (ASTR540) - The University of Arizona

  10. Lens equation – ray tracing lens equation: Structures and Dynamics of Galaxies (ASTR540) - The University of Arizona

  11. Lens equation – ray tracing Solutions (image positions) of the lens equation Structures and Dynamics of Galaxies (ASTR540) - The University of Arizona

  12. Magnification and Distortion Bartelmann & Narayan Structures and Dynamics of Galaxies (ASTR540) - The University of Arizona

  13. Magnification and Distortion • Distortion • Magnification circular symmetric lens Structures and Dynamics of Galaxies (ASTR540) - The University of Arizona

  14. Magnification and Distortion Meneghetti Structures and Dynamics of Galaxies (ASTR540) - The University of Arizona

  15. Magnification and Distortion Wambsganss Structures and Dynamics of Galaxies (ASTR540) - The University of Arizona

  16. Summary Structures and Dynamics of Galaxies (ASTR540) - The University of Arizona

  17. Example MG2016+112

  18. Structures and Dynamics of Galaxies (ASTR540) - The University of Arizona

  19. Lensed Quasar Host Galaxies Mostly based on Chien Y. Peng’s PhD thesis

  20. Basic approach • Model light profiles of foreground and lensed images - using Sersic, exponential and Gaussian functions and PSF’s • Raytracing from image to source plane deflection angle magnification tensor • Approximate lens model by softened isothermal ellipsoids • Produce light profiles and convolve with PSF • ² minimization Structures and Dynamics of Galaxies (ASTR540) - The University of Arizona

  21. Softened Isothermal Ellipsoid (SIE) • Used to model mass distribution of lensing galaxies • Density profile follows roughly  r-2 (tracking dark and baryonic matter) • Central cusp eliminates an quasar image near the center of the lensing galaxy • Projected mass distribution • b: mass parameter, determines size of Einstein ring • q: axis ratio Structures and Dynamics of Galaxies (ASTR540) - The University of Arizona

  22. Lensfit algorithm • Approximate AGN by Gaussian. Fit lensed positions and flux until Gaussian gets Delta distribution • Correct for flux uncertainties due to microlensing • Add shear and add SIE for neighboring galaxies • Replace Gaussian by PSF • Introduce host galaxy – to predict extended arcs • Optimize everything simultaneously Use previously constrained models where available Structures and Dynamics of Galaxies (ASTR540) - The University of Arizona

  23. MG2016+112 - revisited Structures and Dynamics of Galaxies (ASTR540) - The University of Arizona

  24. MG2016+112 - revisited • Host magnitude 22.49mag • Best fitted by a Sersic n=4 • Re=0.82kpc • Quasar magnitude 21.61mag Structures and Dynamics of Galaxies (ASTR540) - The University of Arizona

  25. Survey results 30 observed systems 1<z<4.5 • Early-type Sersic indices for half of the galaxies • Small sizes Re 6kpc • Luminous ellipticals are in a minority as hosts • Bulges gain in mass by a factor of 3-6 • Relationship between BH and bulge luminosity unchanged compared to low-redshifts Structures and Dynamics of Galaxies (ASTR540) - The University of Arizona

  26. Quasar Microlensing

  27. Stars, brown dwarfs, black holes, gas clouds, MACHO’s etc. perturb general magnification pattern Structures and Dynamics of Galaxies (ASTR540) - The University of Arizona

  28. Nothing ist static – lensing objects, source and observer moves • ------ANIMATION------ Structures and Dynamics of Galaxies (ASTR540) - The University of Arizona

  29. Goals of quasar microlensing • Properties of matter along line of sight (dark matter, etc.) • Mass of lensing object • Size of quasar accretion disk • 2D brightness profile of quasar accretion disk Structures and Dynamics of Galaxies (ASTR540) - The University of Arizona

  30. Basic approach to interpret data • Create magnification pattern distribute stars randomly draw those stars from IMF • Convolve with accretion disk model • Randomly create light curves • Determine probability distributions for physical parameters Structures and Dynamics of Galaxies (ASTR540) - The University of Arizona

  31. Thin accretion disk model • Black hole is surrounded by a thermally radiating disk with a temperature profile of • Gives surface brightness profile • Latter expression neglects central temperature depression • Exponential surface brightness drop after Structures and Dynamics of Galaxies (ASTR540) - The University of Arizona

  32. Quasar Microlensing: Q2237+0305 J. Wambsganss Structures and Dynamics of Galaxies (ASTR540) - The University of Arizona

  33. C. Kochanek 2004 Structures and Dynamics of Galaxies (ASTR540) - The University of Arizona

  34. C. Kochanek 2004 Structures and Dynamics of Galaxies (ASTR540) - The University of Arizona

  35. Quasar Microlensing: Q2237+0305 C. Kochanek et al 2006 Structures and Dynamics of Galaxies (ASTR540) - The University of Arizona

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