Systematic uncertainties in gravitational lensing models: a semi-analytical study of PG1115+080

Abstract

While the Hubble constant can be derived from observable time delays between images of lensed quasars, the result is often highly sensitive to assumptions and systematic uncertainties in the lensing model. Unlike most previous authors we explore a broad class of models with non-parametric lens radial profile and allow for non-elliptical lens potentials. The axis ratio and position angle of the lens can be determined from the image positions of quadruple gravitational lensed systems by solving the lens equation semi-analytically, independent of the radial profile. We give simple equations for estimating the power-law slope of the lens density directly from the image positions and for estimating the time delay ratios. Our method greatly simplifies the numerics for fitting observations and is fast in exploring the model parameter space. As an illustration we apply the model to PG1115+080. We show that the measured image positions and time delays do not uniquely determine the Hubble constant. The mass-to-light ratio of the lens galaxy increases with radius, higher at image C than at image B.

Some small corrections and clarifications added. 20 pages, 11 figures, accepted by MNRAS

References in corpus (3)

• A Determination of H_0 with the CLASS Gravitational Lens B1608+656: I. Time Delay Measurements with the VLA
• Pixelated Lenses and H_0 from Time-delay QSOs
• Infrared Imaging of the Gravitational Lens PG 1115+080 with the Subaru Telescope

Cited by in corpus (20)

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• Testing Bekenstein's Relativistic MOND gravity with Lensing Data
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• Multipole Models of Four-Image Gravitational Lenses with Anomalous Flux Ratios
• Halo Structures of Gravitational Lens Galaxies
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• The Lens Galaxy In PG1115+080 is an Ellipse
• What Makes Quadruply Lensed Quasars Quadruple?
• A new method for the estimate of H_0 from quadruply imaged gravitational lens systems
• Intrinsic Degeneracy of Gravitational Lens Time Delays: the case for a simple quadruple system in $\Lambda$CDM cosmology
• Gravitational lensing potential reconstruction in quadruply imaged systems
• Lens modelling and H_0 estimate in quadruply lensed systems
• PG 1115+080: variations of the A2/A1 flux ratio and new values of the time delays
• Time delays in PG1115+080: new estimates