Illustrations note XI, p. Other books in this series.
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Strong gravitational lensing
Colloids and the Depletion Interaction Henk N. Back cover copy This book contains a complete and up-to-date review of gravitational lensing, focussing on recent progress in both observations and theory. The mapping of dark matter on galaxy and cluster sized scales, as will be seen through the future eyes of ALMA, is discussed.
The lensing of quasars is presented as a method for measuring cosmological parameters and recent observations and modeling are examined. In the regime of weak gravitational lensing numerous results are now available and are compared with simulations at different length-scales. The use of weak lensing around isolated galaxies to measure the shape of galaxy halos is studied. Absorption lines of lensed quasars can be used to map the occulting systems out to a redshift of 2 and this technique is investigated.
This book is designed for researchers and graduate students interested in any research area of gravitational lensing. Much of his theories have already been confirmed by observation including the bending of light waves by a massive object. Such proof was witnesses as stars near the Sun were shown to shift positions — observed during a solar eclipse. On a much larger scale, massive objects like black holes and brown dwarfs also bend distant light rays as do galaxies and galaxy clusters.
When using massive objects like galaxies and galaxy clusters to examine the bending of these light rays, the gravity of these objects acts like a lens. This effect is called gravitational lensing and has proven very effective in observing some of the most exotic phenomenon such as exoplanets and quasars. Even more remarkable is the use of gravitational lensing to detect and map dark matter regions surrounding galaxies and galaxy clusters.
Strong gravitational lensing - Wikipedia
By using a gravity lens, the detection of dark matter has been confirmed and is providing valuable data for cosmologists to help mold the theories involving the constituents and origins of dark matter. Back to Top Back to Cosmology. A Gravitational Lens :. The presence of mass within space-time creates a curve or depression in the fabric of space-time.
The common analogy of this is the rubber sheet. Figure 1.
Figure 1 shows an example of the rubber sheet, with a mass — that is invisible in this example — that has created a depression within space-time. As light waves indicated in blue pass close to the curved space, its path is altered resulting is a bending of light. For the lens to work properly, the source of the light must be in the line of sight to the observer with the massive object in between.
This basic two dimensional lens demonstrates a correlation between length and angles based on the radius of influence by the massive object. Figure 2. Figure 2 is a graphical example of this two dimensional lens. The point L is the massive object while point S1 is the distant object.
S is the apparent position of the object to the observer; O. S2 is ignored in this example. This equation right demonstrates the basic properties of the lens effect in figure 2 the following examples: Wambsgauss, It is important to state that several correlations exist with the basic lens equation that carries over to real world examples. The length to the lenses object is correlated to the distance to the lensing object L by the following equation:.
This directly translates to a correlation to the angles involved:. This is an important realization as this gives astronomers a tool for measuring the strength of a gravity lens with the benefit of helping to determine the distance as well. As a summary, the above example can be put together to form the Einstein Radius, the radius of influence by the lensing object:. So what would a gravity lens look like for a familiar object? Figure 3. The above image demonstrates what an invisible mass would do if placed between us and the Mona Lisa.
The point source is tiny with a mass of the planet Saturn. Notice the obvious circular effect of the lens — the radius.
Gravitational Lensing: An Astrophysical Tool
Also notice the tiny nose and the small arc of the mouth within the radius. The overall image is also bloated — spread out as a result of the lensing. This is a typical effect of the gravity lens. The Gravity Lens in use :. On September 13, , the Hubble Space Telescope issued a press release of what is probably the most famous of all images of a gravity lens:.
Figure 4. This particular arrangement is called the Einstein Cross. The four points of the cross are a lenses distant quasar, 8 billion light years away.
Strong lensing is the result of a lensing object splitting the lensed object into separate distinct images — like our Einstein Cross example above. Strong lensing can also produced a large number of arcs as well. The usual targets for strong lensing are clusters of galaxies.
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By studying the strength of the lens, the astronomers learn about the mass distribution throughout the cluster. Weak lensing is defined by arcs of the lensed object by a lensing object. Figure 5. I'd like to read this book on Kindle Don't have a Kindle? No customer reviews.
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