On model-dependent bounds on H(0) from gravitational images Application of Q0957 + 561A,B

Falco, E.; Gorenstein, M. V.; Shapiro, I. I.

doi:10.1086/184422

Cited by 401 publications

(391 citation statements)

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“…This is the mass-disk degeneracy, Ðrst noted by Falco, Gorenstein, & Shapiro (1985) and discussed in several recent papers (e.g., Saha 2000) ; basically it means that steeper lens proÐles give higher from the same dataÈsee H 0 the "" radial index versus h ÏÏ plots in WS for examples. This particular degeneracy is exact, but numerically one can cook up any number of near-degeneracies that scale H 0 signiÐcantly while producing only slight, observationally negligible, changes in rings.…”

Section: Rings and The Arrival-time Surfacementioning

confidence: 87%

Beware the Nonuniqueness of Einstein Rings

Saha¹,

Williams²

2001

The Astronomical Journal

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We explain how an approximation to the rings formed by the host galaxies in lensed QSOs can be inferred from the QSO data alone. A simple ring image can be made from any lens model by a simple piece of computer graphics : just plot a contour map of the arrival-time surface with closely spaced contours. We go on to explain that rings should be (1) sensitive to time-delay ratios between di †erent pairs of images, but (2)

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Section: Rings and The Arrival-time Surfacementioning

confidence: 87%

Beware the Nonuniqueness of Einstein Rings

Saha¹,

Williams²

2001

The Astronomical Journal

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“…For example, mass sheet degeneracy, and some other degeneracies where different lenses reproduce exactly the same image observables have been well studied (Falco et al 1985;Gorenstein et al 1988;Saha 2000;Liesenborgs & De Rijcke 2012), especially in relation to mass modeling, where degeneracies affect E-mail:…”

Section: Introductionmentioning

confidence: 99%

Model-free analysis of quadruply imaged gravitationally lensed systems and substructured galaxies

Woldesenbet

Williams

2015

Mon. Not. R. Astron. Soc.

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Multiple image gravitational lens systems, and especially quads are invaluable in determining the amount and distribution of mass in galaxies. This is usually done by mass modeling using parametric or free-form methods. An alternative way of extracting information about lens mass distribution is to use lensing degeneracies and invariants. Where applicable, they allow one to make conclusions about whole classes of lenses without model fitting. Here, we use approximate, but observationally useful invariants formed by the three relative polar angles of quad images around the lens center to show that many smooth elliptical+shear lenses can reproduce the same set of quad image angles within observational error. This result allows us to show in a model-free way what the general class of smooth elliptical+shear lenses looks like in the three dimensional (3D) space of image relative angles, and that this distribution does not match that of the observed quads. We conclude that, even though smooth elliptical+shear lenses can reproduce individual quads, they cannot reproduce the quad population. What is likely needed is substructure, with clump masses larger than those responsible for flux ratio anomalies in quads, or luminous or dark nearby perturber galaxies.

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“…In fact, strong lensing provides a robust measurement of the total mass projected inside the Einstein radius (Kochanek 1991), breaking the mass-anisotropy degeneracy of the dynamical analysis, after which stellar dynamics, giving constraints on the total mass distribution at small radii (typically R e ), provides an estimate of the mass gradient. Thus, a joint strong lensing and stellar-dynamical study can be used to determine the average logarithmic density slope of the total mass inside the Einstein radius of individual lens galaxies, independent of the mass-sheet degeneracy (e.g., Falco et al 1985;Kochanek 2006). In addition, this allows one to decompose the total mass distribution into luminous and dark with good precision, making feasible an investigation of the evolution of the internal structure of early-type galaxies.…”

Section: Introductionmentioning

confidence: 99%

Projected Central Dark Matter Fractions and Densities in Massive Early-Type Galaxies From the Sloan Digital Sky Survey

Grillo

2010

ApJ

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We investigate in massive early-type galaxies the variation of their two-dimensional central fraction of dark over total mass and dark matter density as a function of stellar mass, central stellar velocity dispersion, effective radius, and central surface stellar mass density. We use a sample of approximately 1.7 × 10 5 galaxies from the Sloan Digital Sky Survey Data Release Seven (SDSS DR7) at redshift smaller than 0.33. We apply conservative photometric and spectroscopic cuts on the SDSS DR7 and the MPA/JHU value-added galaxy catalogs, to select galaxies with physical properties similar to those of the lenses studied in the Sloan Lens ACS Survey. The values of the galaxy stellar and total mass projected inside a cylinder of radius equal to the effective radius are obtained, respectively, by fitting the SDSS multicolor photometry with stellar population synthesis models, under the assumption of a Chabrier stellar initial mass function (IMF), and adopting a one-component isothermal total mass model with effective velocity dispersion approximated by the central stellar velocity dispersion. The plausibility of an isothermal model to represent the galaxy total mass distribution is supported by independent gravitational lensing and stellar-dynamical analyses performed in the lens subsample, which is found here to represent nicely the entire galaxy sample. We find that within the effective radius the stellar mass estimates differ from the total ones by only a relatively constant proportionality factor. In detail, we observe that the values of the projected fraction of dark over total mass and the logarithmic values of the central surface dark matter density (measured in M kpc −2 ) have almost Gaussian probability distribution functions, with median values of 0.64 +0.08 −0.11 and 9.1 +0.2 −0.2 , respectively. We discuss the observed correlations between these quantities and other galaxy global parameters and show that our results disfavor an interpretation of the tilt of the fundamental plane in terms of differences in the galaxy dark matter content and give useful information on the possible variations of the galaxy stellar IMF and dark matter density profile. Finally, we provide some observational evidence on the likely significant contribution of dry minor mergers, feedback from active galactic nuclei, and/or coalescence of binary black holes on the formation and evolution of massive early-type galaxies.

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On model-dependent bounds on H(0) from gravitational images Application of Q0957 + 561A,B

Cited by 401 publications

References 0 publications

Beware the Nonuniqueness of Einstein Rings

Beware the Nonuniqueness of Einstein Rings

Model-free analysis of quadruply imaged gravitationally lensed systems and substructured galaxies

Projected Central Dark Matter Fractions and Densities in Massive Early-Type Galaxies From the Sloan Digital Sky Survey

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