Cluster lenses

Abstract

Clusters of galaxies are the most recently assembled, massive, bound structures in the Universe. As predicted by General Relativity, given their masses, clusters strongly deform space-time in their vicinity. Clusters act as some of the most powerful gravitational lenses in the Universe. Light rays traversing through clusters from distant sources are hence deflected, and the resulting images of these distant objects therefore appear distorted and magnified. Lensing by clusters occurs in two regimes, each with unique observational signatures. The strong lensing regime is characterized by effects readily seen by eye, namely, the production of giant arcs, multiple images, and arclets. The weak lensing regime is characterized by small deformations in the shapes of background galaxies only detectable statistically. Cluster lenses have been exploited successfully to address several important current questions in cosmology: (i) the study of the lens(es)-understanding cluster mass distributions and issues pertaining to cluster formation and evolution, as well as constraining the nature of dark matter; (ii) the study of the lensed objects-probing the properties of the background lensed galaxy population-which is statistically at higher redshifts and of lower intrinsic luminosity thus enabling the probing of galaxy formation at the earliest times right up to the Dark Ages; and (iii) the study of the geometry of the Universe-as the strength of lensing depends on the ratios of angular diameter distances between the lens, source and observer, lens deflections are sensitive to the

Observational probes of cosmic acceleration

“…The excellent review by Allen et al (2011) discusses other cosmological applications of clusters and examines recent cluster abundance results in detail (see also the earlier review by Voit 2005); we summarize recent work in §6.2 but devote most of our attention to methods for Stage III and Stage IV cluster surveys. Other recent reviews in the field include Kravtsov and Borgani (2012), who review the physics of cluster formation with emphasis on the insights gained from hydrodynamic cosmological simulations, and Kneib and Natarajan (2011), who review strong and weak lensing by clusters.…”

Mass and magnification maps for the Hubble Space Telescope Frontier Fields clusters: implications for high-redshift studies

“…Soucail et al 1988) and the realization that they can be explained by gravitational lensing (the bending of light by massive foreground mass concentrations) opened a new and powerful route to studying the distant Universe. Gravitational lensing can be understood as a geometrical mapping of the source plane on to the image plane, a mapping that depends on the surface mass distribution in the deflector and on the angular-diameter dis-E-mail: johan.richard@univ-lyon1.fr tances between the observer and the source, and the lens and the source, respectively (see the review by Kneib & Natarajan 2011). For extreme mass concentrations, the mapping is non-linear, producing magnified and highly distorted multiple images of a single background source.…”

Cosmology through arc statistics I: sensitivity to Ωmand σ8

“…Being the most massive structures in the Universe, galaxy clusters are also the most powerful gravitational lenses (Narayan & Bartelmann 1999;Bartelmann & Schneider 2001;Kneib & Natarajan 2011). In particular, they are responsible for highly non-linear lensing effects taking place in their densest regions, i.e.…”

“…in their cores. In this so-called "strong" lensing regime, the images of background galaxies are heavily distorted, often leading to the appearance of gravitational arcs with large length-to-width ratios (see Kneib & Natarajan 2011;Meneghetti et al 2013, and references therein).…”