title: A combined observational and theoretical study of gravitationally lensed quasars
creator: Anguita, Timo
subject: ddc-520
subject: 520 Astronomy and allied sciences
description: In this thesis we study gravitational lensing of quasars, from strong lensing to microlensing. We investigate one strong lens candidate recently discovered in the COSMOS field: COSMOS 5921+0638. Our analysis of the nature of the lens reveals that the system is composed of an early type foreground galaxy at redshift z_l=0.551+/-0.001 lensing a background low luminosity AGN and its host galaxy at a candidate redshift of z_s=3.14+/-0.05. We show that flux anomalies observed in the lensed images are likely due to substructure or microlensing by stars in the lensing galaxy. Extending the analysis of the optical emission of lensed quasars, we have used integral field spectroscopy to study four gravitationally lensed quasar systems: HE 0230-2130, RX J0911+0551, H 1413+117 and B 1359+154, as well as objects in their line-of-sight. The first three systems show anomalous flux ratios consistent with microlensing by stars in their lensing galaxies. In the final part of this work, we probe the structure of the accretion disk of the lensed quasar Q 2237+0305 by the analysis of a high magnification microlensing event seen in the so-called "image C" of the system in the year 1999. Using multi-band observations and microlensing simulations, we measure an accretion disk size of Gaussian width sigma_g'=4.6^{+3.4}_-3.4} x 10^15 sqrt{M/0.1M_sun} cm and a ratio sigma_r'/sigma_g'=1.3^{+0.5}_{-0.2}, without the use of any prior, and of Gaussian width sigma_g'=1.3^{+0.2}_{-0.7} x 10^15 sqrt{M/0.1M_sun} cm and a ratio sigma_r'/sigma_g'=1.5^{+0.9}_{-0.3} with a prior on the relative velocity between source and microlenses. Both results are in agreement with the predictions of a standard Shakura-Sunyaev disk model. The use of multi-band observations revealed that the magnification event seen in image C of Q~2237+0305 was produced by a caustic crossing with a confidence greater than 74%. 
date: 2009
type: Dissertation
type: info:eu-repo/semantics/doctoralThesis
type: NonPeerReviewed
format: application/pdf
identifier: https://archiv.ub.uni-heidelberg.de/volltextserverhttps://archiv.ub.uni-heidelberg.de/volltextserver/9411/1/ANGUITA_thesis.pdf
identifier: DOI:10.11588/heidok.00009411
identifier: urn:nbn:de:bsz:16-opus-94111
identifier:   Anguita, Timo  (2009) A combined observational and theoretical study of gravitationally lensed quasars.  [Dissertation]     
relation: https://archiv.ub.uni-heidelberg.de/volltextserver/9411/
rights: info:eu-repo/semantics/openAccess
rights: http://archiv.ub.uni-heidelberg.de/volltextserver/help/license_urhg.html
language: eng