What is the largest Einstein radius in the universe?

Oguri, Masamune; Blandford, R. D.

doi:10.1111/j.1365-2966.2008.14154.x

Cited by 139 publications

(323 citation statements)

References 162 publications

(275 reference statements)

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“…If the properties of real clusters are reproduced correctly by the clusters in our simulations, these very efficient strong lenses are likely to have extremely biased 2D-concentrations, as recently reported by Broadhurst et al (2008) (see also ). Our findings agree with the results recently published by Oguri & Blandford (2009), who use semianalytic models of triaxial halos to estimate that the projected mass distributions of strong lensing clusters have ∼40−60% higher concentrations than typical clusters with similar redshifts and masses (see also Sereno et al 2010). …”

Section: Concentrationssupporting

confidence: 92%

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Strong lensing in the MARENOSTRUM UNIVERSE

Meneghetti

Fedeli

Pace

et al. 2010

A&A

152

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Context. Strong lensing is one of the most direct probes of mass distribution in the inner regions of galaxy clusters. It can be used to constrain the density profiles and to measure the mass of the lenses. Moreover, the abundance of strong lensing events can be used to constrain structure formation and cosmological parameters through the so-called "arc-statistics" approach. However, several issues related to the use of strong lensing clusters in cosmological applications are still controversial, leading to the suspicion that several biases may affect this very peculiar class of objects. Aims. With this study we aim a better understanding of the properties of galaxy clusters that can potentially act as strong lenses. Methods. We do so by investigating the properties of a large sample of galaxy clusters extracted from the N-body/hydrodynamical simulation MareNostrum Universe. We perform ray-tracing simulations with each of them and identify those objects capable of producing strong lensing effects. We explore the correlation between the cross section for lensing and many properties of clusters, such as mass, three-dimensional and projected shapes, their concentrations, the X-ray luminosity, and the dynamical activity. Results. We quantify the minimal cluster mass required for producing both multiple images and large distortions. While we do not measure a significant excess of triaxiality in strong lensing clusters, we find that the probability of strong alignments between the major axes of the lenses and the line of sight is a growing function of the lensing cross section. In projection, the strong lenses appear rounder within R 200 , but we find that their cores tend to be more elliptical as the lensing cross section increases. As a result of the orientation bias, we also find that the cluster concentrations estimated from the projected density profiles tend to be biased high. The X-ray luminosity of strong lensing clusters tend to be higher than for normal lenses of similar mass and redshift. This is particularly significant for the least massive lenses. Finally, we find that the strongest lenses generally exhibit an excess of kinetic energy within the virial radius, thus indicating that they are more dynamically active than the usual clusters. Conclusions. We conclude that strong lensing clusters are a very peculiar class of objects, affected by many selection biases that need to be properly modeled when using them to study the inner structure of galaxy clusters or to constrain the cosmological parameters.

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Section: Concentrationssupporting

confidence: 92%

“…Oguri & Blandford (2009) (OB hereafter) used semi-analytic methods based on triaxial NFW halos for calculating the probability distributions of several properties of the clusters producing the largest critical lines in the universe. The size of the critical lines is quantified by means of the Einstein radius (see Eq.…”

Section: Discussionmentioning

confidence: 99%

Strong lensing in the MARENOSTRUM UNIVERSE

Meneghetti

Fedeli

Pace

et al. 2010

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152

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“…Thus the CDF will be steeper, resulting in a more conservative estimate of the occurrence probability of a given Einstein radius. In comparison to the previously discussed distributions that assumed a z s = 2.0, the higher source redshift will shift the distribution to larger Einstein radii due to the modified lensing geometry, as discussed in Oguri & Blandford (2009).…”

Section: The Probability Of Occurrence Of the Critical Curvementioning

confidence: 74%

The strongest gravitational lenses

Waizmann

Redlich

Bartelmann

2012

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Context. With the amount and quality of galaxy cluster data increasing, the question arises whether or not the standard cosmological model can be questioned on the basis of a single observed extreme galaxy cluster. Usually, the word extreme refers directly to cluster mass, which is not a direct observable and thus subject to substantial uncertainty. Hence, it is desirable to extend studies of extreme clusters to direct observables, such as the Einstein radius. Aims. We aim to evaluate the occurrence probability of the large observed Einstein radius of MACS J0717.5+3745 within the standard ΛCDM cosmology. In particular, we want to model the distribution function of the single largest Einstein radius in a given cosmological volume and to study which underlying assumptions and effects have the strongest impact on the results. Methods. We obtain this distribution by a Monte Carlo approach, based on the semi-analytic modelling of the halo population on the past lightcone. After sampling the distribution, we fit the results with the general extreme value (GEV) distribution which we use for the subsequent analysis. Results. We find that the distribution of the maximum Einstein radius is particularly sensitive to the precise choice of the halo mass function, lens triaxiality, the inner slope of the halo density profile and the mass-concentration relation. Using the distributions so obtained, we study the occurrence probability of the large Einstein radius of MACS J0717.5+3745, finding that this system is not in tension with ΛCDM. We also find that the GEV distribution can be used to fit very accurately the sampled distributions and that all of them can be described by a (type-II) Fréchet distribution. Conclusions. With a multitude of effects that strongly influence the distribution of the single largest Einstein radius, it is more than doubtful that the standard ΛCDM cosmology can be ruled out on the basis of a single observation. If, despite the large uncertainties in the underlying assumptions, one wanted to do so, a much larger Einstein radius ( > ∼ 100 ) than that of MACS J0717.5+3745 would have to be observed.

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“…Furthermore we neglected the influence of halo triaxiality (see Blandford 2009 andHamana et al 2012). This effect will introduce an additional scatter into the detection amplitude.…”

Section: Correction Termmentioning

confidence: 99%

Extreme value statistics of weak lensing shear peak counts

Reischke

Maturi

Bartelmann

2015

Mon. Not. R. Astron. Soc.

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The statistics of peaks in weak gravitational lensing maps is a promising technique to constrain cosmological parameters in present and future surveys. Here we investigate its power when using general extreme value statistics which is very sensitive to the exponential tail of the halo mass function. To this end, we use an analytic method to quantify the number of weak lensing peaks caused by galaxy clusters, large-scale structures and observational noise. Doing so, we further improve the method in the regime of high signal-to-noise ratios dominated by non-linear structures by accounting for the embedding of those counts into the surrounding shear caused by large scale structures. We derive the extreme value and order statistics for both over-densities (positive peaks) and under-densities (negative peaks) and provide an optimized criterion to split a wide field survey into sub-fields in order to sample the distribution of extreme values such that the expected objects causing the largest signals are mostly due to galaxy clusters. We find good agreement of our model predictions with a ray-tracing N -body simulation. For a Euclid-like survey, we find tight constraints on σ 8 and Ω m with relative uncertainties of ∼ 10 −3 . In contrast, the equation of state parameter w 0 can be constrained only with a 10% level, and w a is out of reach even if we include redshift information.

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What is the largest Einstein radius in the universe?

Cited by 139 publications

References 162 publications

Strong lensing in the MARENOSTRUM UNIVERSE

Strong lensing in the MARENOSTRUM UNIVERSE

The strongest gravitational lenses

Extreme value statistics of weak lensing shear peak counts

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