Evidence for substructure in lens galaxies
Shude Mao,Peter Schneider +1 more
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TLDR
In this article, the authors argue that the discrepancy between observed and model-predicted flux ratios is due to substructure in the lens, and propose a strategy to model lens systems in which substructure is suspected.Abstract:
We discuss whether one should expect that multiply imaged QSOs can be understood with `simple' lens models which contain a handful of parameters. Whereas for many lens systems such simple mass models yield a remarkably good description of the observed properties, there are some systems which are notoriously difficult to understand quantitatively. We argue that at least in one case (B 1422+231) these difficulties are not due to a `wrong' parametrization of the lens model, but that the discrepancy between observed and model-predicted flux ratios are due to substructure in the lens. Similar to microlensing for optical fluxes, such substructure can distort also the radio flux ratios predicted by `simple' mass models, in particular for highly magnified images, without appreciably changing image positions. Substructure also does not change the time delay significantly and therefore has little effect on the determination of the Hubble constant using time delays. We quantify these statements with several simple scenarios for substructure, and propose a strategy to model lens systems in which substructure is suspected.read more
Citations
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Dark Matter Substructure within Galactic Halos
Ben Moore,Sebastiano Ghigna,Fabio Governato,George Lake,Thomas R. Quinn,Joachim Stadel,Paolo Tozzi +6 more
TL;DR: In this article, the substructure clumps are on orbits that take a large fraction of them through the stellar disk, leading to significant resonant and impulsive heating, and the model predicts that the virialized extent of the Milky Way's halo should contain about 500 satellites with circular velocities larger than the Draco and Ursa Minor systems, i.e., bound masses 108 M☉ and tidally limited sizes 1 kpc.
Journal ArticleDOI
Ultralight scalars as cosmological dark matter
TL;DR: Fuzzy dark matter (FDM) as discussed by the authorsDM is an alternative to CDM, which is an extremely light boson having a de Broglie wavelength inside the galaxy.
Journal ArticleDOI
Clumps and streams in the local dark matter distribution
TL;DR: A simulation that resolves dark matter substructure even in the very inner regions of the Galactic halo is reported, finding hundreds of very concentrated dark matter clumps surviving near the solar circle, as well as numerous cold streams.
Journal ArticleDOI
Reionization and the abundance of galactic satellites
TL;DR: In this paper, a simple model for the formation and evolution of dark halos, based on the extended Press-Schechter formalism and tested against N-body results, is presented.
Journal ArticleDOI
Direct Detection of Cold Dark Matter Substructure
TL;DR: In this paper, the abundance of satellite halos in a sample of seven lens systems was measured using Monte Carlo simulations and the critical radius for the satellites was estimated for a dn/dM M-1.8 (Mlow < M < Mhigh) satellite mass function.
References
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Journal ArticleDOI
On the possibility of determining Hubble's parameter and the masses of galaxies from the gravitational lens effect
Journal ArticleDOI
Flux variations of QSO 0957 + 561 A, B and image splitting by stars near the light path
K. Chang,S. Refsdal +1 more
TL;DR: In this paper, the double QSO 0957 + 561 A, B is the result of gravitational lens actions by a massive galaxy, stars in its outer parts and close to the light paths may cause significant flux changes in one year.
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TL;DR: This book explains the theory underlying the classical statistical methods using confidence intervals, hypothesis testing, and the theory of tests; estimation (including maximum likelihood); goodness of fit; and non-parametric and rank tests.
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Shear and ellipticity in gravitational lenses
TL;DR: In this paper, an independent shear axis can be produced by misalignments between the luminous galaxy and its dark matter halo, or by external shear perturbations due to galaxies and clusters correlated with the primary lens or along the line of sight.
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