Macro- and Micromodels for Gravitational Lenses
Abstract
General aspects of the modeling of gravitationally lensed objects are discussed. A new superposition principle for deflector models is introduced, and the consequences of the nonuniqueness of lens models are discussed. Special emphasis is placed on the time delay and on the determination of the Hubble parameter and the lens mass. Contrary to common belief, the determination of the lens mass is not independent of the shear due to the distribution of the matter around the lens. In general, the use of macrolensing as a "cosmological tool" is limited by our ignorance of the distribution of (especially dark) matter. If time delay ratios can be measured, the parameter space of the lens model can be significantly reduced, thereby allowing more accurate estimates of the lens mass. Possible parameters to describe microlensing light curves are discussed and analyzed with respect to their usefulness for obtaining information on the macromodel and on the distribution of compact objects in the lens. The accurate determination of light curve parameters (like, e.g., the frequency of high amplification events) requires, however, monitoring over some hundred years. New lens models are presented for the classical double quasar 0957+561A,B, from which a lens mass of ~ 6 x 10^11^ M_sun_ is derived. Although no high amplification events can be identified in the published light curves of the two images of 0957+561, weak constraints can be placed on the size of the continuum source of this quasar. If we assume that the relative transverse velocity between the quasar and the microlensing caustics does not exceed 1000 km s^-1^, the continuum source should be smaller than ~ 2.8 x 10^-3^ pc.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- July 1990
- DOI:
- 10.1086/168921
- Bibcode:
- 1990ApJ...357..309K
- Keywords:
-
- Astronomical Models;
- Cosmology;
- Gravitational Lenses;
- Hubble Constant;
- Light Curve;
- Quasars;
- Computational Astrophysics;
- Energy Sources;
- Radio Galaxies;
- Relativistic Theory;
- Astrophysics;
- COSMOLOGY;
- GRAVITATIONAL LENSES;
- QUASARS