Critical curve
A critical curve in a gravitational lens is the region around the gravitational lens where the magnification is maximum[1][2]. For circularly symmetric lenses, critical curves are circular and have a radius equal to the Einstein radius. Critical curves can be mapped into the source plane into similar curves which are referred to as caustics, similar to the caustics produced by regular lenses. A galaxy, or source, that is located at the caustic of a circularly symmetric lens forms an Einstein ring. Although usually represented in the plane of the source, caustics actually form in the observer plane.
Galaxies that are observed near critical curves can be magnified by large factors. Smaller objects like Quasars or stars can be magnified by much larger factors since they are smaller. The largest magnifications near critical curves have been observed for stars with magnification factors exceeding 1,000. Examples of stars observed at the critical curve, or very close to it are Icarus, Godzilla or Earendel.
See also
- Einstein ring
References
- ↑ Schneider, Peter; Ehlers, Jürgen; Falco, Emilio E. (1992). Gravitational Lenses. Springer-Verlag Berlin Heidelberg New York Press. ISBN 978-3-540-97070-5. Search this book on
- ↑ Narayan, R.; Bartelmann, M. (1996). "Lectures on Gravitational Lensing". arXiv:astro-ph/9606001. Bibcode:1996astro.ph..6001N.
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