A gravitational lens can occur when a huge amount of matter, like a cluster of galaxies, creates a gravitational field that distorts and magnifies the light from distant galaxies that are behind it but in the same line of sight.
The effect is like looking through a giant magnifying glass..
The first gravitational lens was discovered in 1979, when two quasars were discovered very close to each other in the sky and with similar distances and spectra.
The two quasars were actually the same object whose light had been split into two paths by the gravitational influence of an intervening galaxy..
A gravitational lens can occur when a huge amount of matter, like a cluster of galaxies, creates a gravitational field that distorts and magnifies the light from distant galaxies that are behind it but in the same line of sight.
The effect is like looking through a giant magnifying glass..
This effect is known as gravitational microlensing.
The simplest type of gravitational lensing occurs when there is a single concentration of matter at the center, such as the dense core of a galaxy.
The light of a distant galaxy is redirected around this core, often producing multiple images of the background galaxy..
Noun. lensing (countable and uncountable, plural lensings) The focussing of light as if by a lens. (slang) The process of shooting a film..
Weak gravitational lensing, the tiny distortions in background galaxy shapes, sizes, and fluxes due to the deflection by mass in more nearby objects, is a powerful probe of dark matter and dark energy..
Strong lensing of LISA target sources (supermassive BHs) has been discussed in ref. 32, and 33 proposed to use the statistics of strongly lensed sources or the time-delay measurements of lensed GW signals to constrain cosmological parameters without identifying the EM counterparts.
Weak gravitational lensing maps source galaxies to new positions on the sky, systematically distorting their images.
The resulting shear γ of their images is related to the projected foreground mass contrast inside an angular radius θ: γt =<κ(<θ)> -κ(θ) where γt is the tangential component of the shear, κ = Σ / Σc is the dimensionless mass surface .
Weak lensing has high information content.
A big advantage for WL over CMB is Tomography.
The rich cosmological harvest from CMB comes from a single redshift of 1100, but because dark energy creates a change in observables as a function of redshift, CMB data alone is relatively insensitive to dark energy model parameters.
If we know distances to so.
Such improvements translate to tighter cosmological constraints when shear ratios are combined with cosmic shear and other 2pt functions.
For the DES Y3 data, SR improves S8 constraints from cosmic shear by up to 31%, and for the full combination of probes (3x2pt) by up to 10%.
Weak lensing is a powerful probe of cosmological models, beautifully complementary to those that have given rise to the current standard model of cosmology.
The statistics of shear and mass maps on large scales over a wide range in redshift holds much promise for fundamental cosmology.
The underlying physics is extremely simple General Relativity: .
These analysis choices include:
Strong lensing at the galaxy scale is useful for numerous applications in Astrophysics and Cosmology.
Some of the principal applications are studying the mass structure, formation, and evolution of elliptical galaxies, constraining the stellar initial mass function, and measuring cosmological parameters.
