Microlensing
Abstract
This review summarizes the main aspects of microlensing (ML), i.e. the effects of small compact objects on a background source due to gravitational light deflection. After mentioning the basic ML models, the methods to detect ML are discussed. The main effect of ML is magnification, both of multiple images of quasars and of isolated sources. Directly observable is a variation of the magnification in time which causes lens-induced variability. This provides a potential diagnosis for the sources, but is difficult to be separated from intrinsic variability for single image sources. The magnification of sources can lead to the amplification bias, i.e. it can affect the number of sources in flux-limited samples. Consequences of this effect are mentioned, and its possible detections, the most direct of which is the recently found association of high-redshift quasars with (foreground) galaxies, are briefly discussed. The main ML model which has been investigated in detail in the literature (random star field) is considered, and some results are presented. Since ML has been (and is expected to continue to be) a very active field of research, I can only scratch the surface for most topics, and refer the interested reader to the relevant papers. Finally, some remarks about inhomogeneous universes are added.
- Publication:
-
Gravitational Lensing
- Pub Date:
- 1990
- DOI:
- 10.1007/BFb0009226
- Bibcode:
- 1990LNP...360..175S
- Keywords:
-
- Gravitational Lenses;
- Quasars;
- Active Galactic Nuclei;
- Angular Distribution;
- Astronomical Models;
- Magnification;
- Red Shift;
- Astrophysics