Gravitational lensing

Luminous arc An apparent arc of light around a massive object that is causing a gravitational lensed image of galaxies behind. Can be hundreds of light-years in length. 

The existence of dark matter (either baryonic or non-baryonic) is inferred from its gravitational effects on galactic rotation curves, the velocity dispersions and hydrostatic equilibrium of hot (X-ray) gas in clusters and groups of galaxies, gravitational lensing and departures from the smooth Hubble flow described by Eq. (4.1). This dark matter resides at least partly in the halos of galaxies such as our... 

Fig. 12.10. Comparison of the observed spectrum of the gravitationally lensed LBG MS 1512-cB58 (bold), with a redshift of 2.7, with synthetic spectra calculated with Starburst 99 together with the theoretical spectral library WM-basic for various metallicities (faint). The left panels show the region of the A. 1425 complex (a blend of Si, C and Fe photospheric lines), while the right panels show photospheric features of Fe hi between 1900 and 2000 A. After Rix etal. (2004).

For most astronomers, the solution to these cosmological problems resides in a combination of various methods. The luminosity-redshift test must be combined with independent techniques, such as anisotropies in the cosmic background radiation and statistical study of gravitational lenses. 

Observations of galaxy duster do not help in this respect since the available data stop our understanding of the DM density profile at distances r 10 kpc from their centres (see Fig.5.1). Down to these scales the NFW is still allowed and at smaller scales the inner slope remains quite uncertain even when the combined analysis of X-ray, gravitational lensing and galaxy dynamics data are taken into account (Dalai Keeton 2003). 

GRAVITATIONAL LENSING FROM /z-LENSING TO COSMIC SHEAR EXPERIMENTS... 

Abstract These notes present the physics of gravitational lensing in various cosmological contexts. The equations and approximations that are commonly used to describe the displacement field or the amplification effects are presented. Several observational applications are discussed. They range from micro-lensing effects to cosmic shear detection that is a weak lensing effect induced by the large-scale structure of the Universe. The scientific perspectives of this latter application are presented in some details. 

The aim of these lectures is to study the effects of gravitational lenses in those different astrophysical contexts. These notes are voluntarily focused on the fundamental mechanisms and the basic concepts that are useful to describe these effects. A particular emphasis will be put on the subtleties of the scientific exploitation of the cosmic shear surveys. 

The physical mechanisms of gravitational lenses are well known since the foundation of General Relativity. Any mass concentration is going to deflect photons that are passing by with a fraction angle per unit length, 56/5s, given... 

More recently the masses of clusters of galaxies have been determined using the temperature of hot X-ray emission gas in clusters, and by gravitational lensing. These data are discussed in other reports during this School. 

Mpc groups, clusters Virial theorem, X-rays, gravitational lensing (30) 100 0.1... 

Mpc large clusters and superclusters of galaxies weak gravitational lensing, X-ray temperatures, Virial theorem (31, 32, 33, 34) 100 - 300 l O ihi... 

Ap02 Stars made of WIMPs. Point-like particles of stellar mass with gas halos around them, so that the gravitational lensing events they produce are non-grey and so not recognized. Planck mass relics of the evaporation of PBHs. 

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