Jonathan Coles

The Hubble Time Inferred from 10 Time Delay Lenses

We present a simultaneous analysis of 10 galaxy lenses having time delay measurements. For each lens, we derive a detailed free-form mass map, with uncertainties, and with the additional requirement of a shared value of the Hubble parameter across all the lenses. We test the prior involved in the lens reconstruction against a galaxy-formation simulation. Assuming a concordance cosmology, we obtain H = 13.5 Gyr.

A NEW ESTIMATE OF THE HUBBLE TIME WITH IMPROVED MODELING OF GRAVITATIONAL LENSES

This paper examines free-form modeling of gravitational lenses using Bayesian ensembles of pixelated mass maps. The priors and algorithms from previous work are clarified and significant technical improvements are made. Lens reconstruction and Hubble time recovery are tested using mock data from simple analytic models and recent galaxy formation simulations. Finally, using published data, the Hubble time is inferred through the simultaneous reconstruction of 11 time delay lenses. The result is H0−1 = 13.7−1.0+1.8 Gyr (H0 = 71−8+6 km s−1 Mpc −1).

Cosmological parameter determination in free-form strong gravitational lens modelling

We develop a novel statistical strong lensing approach to probe the cosmological parameters by exploiting multiple redshift image systems behind galaxies or galaxy clusters. The method relies on free-form mass inversion of strong lenses and does not need any additional information other than gravitational lensing. Since in free-form lensing the solution space is a high-dimensional convex polytope, we consider Bayesian model comparison analysis to infer the cosmological parameters. The volume of the solution space is taken as a tracer of the probability of the underlying cosmological assumption. In contrast to parametric mass inversions, our method accounts for the mass-sheet degeneracy, which implies a degeneracy between the steepness of the profile and the cosmological parameters. Parametric models typically break this degeneracy, introducing hidden priors to the analysis that contaminate the inference of the parameters. We test our method with synthetic lenses, showing that it is able to infer the assumed cosmological parameters. Applied to the CLASH clusters, the method might be competitive with other probes.

A sampling strategy for high-dimensional spaces applied to free-form gravitational lensing

ABSTRACT We presentanovelproposalstrategyforthe Metropolis-Hastingsalgorithmdesignedtoefficiently sample general convex polytopes in 100 or more dimensions. This improvesupon previous sampling strategies used for free-form reconstruction of gravitationallenses, but is general enough to be applied to other fields. We have written a parallelimplementation within the lens modeling framework GLASS. Testing shows that weare able to produce uniform uncorrelated random samples which are necessary forexploring the degeneracies inherent in lens reconstruction.Keywords: gravitational lensing: strong - methods: numerical - methods: statistical 1 INTRODUCTIONSome inversion problems in astrophysics make it desirable tosearch or sample a high dimensional solution domain S⊂ R n such that Sis bounded by the linear constraintsAx6b (1)where A ∈ R m×n and bis a constant vector. A classic ap-plication is Schwarzschild’s construction of triaxial stellarsystems in equilibrium (Schwarzschild 1979). Given a three-dimensional discretized target density function ρ

Gravitational lens recovery with glass: measuring the mass profile and shape of a lens

We use a new non-parametric gravitational modelling tool { Glass { to determine what quality of data (strong lensing, stellar kinematics, and/or stellar masses) are required to measure the circularly averaged mass prole of a lens and its shape. Glass uses an under-constrained adaptive grid of mass pixels to model the lens, searching through thousands of models to marginalise over model uncertainties. Our key ndings

Gravitational lens modelling in a citizen science context

We develop a method to enable collaborative modelling of gravitational lenses and lens candidates, that could be used by non-professional lens enthusiasts. It uses an existing free-form modelling program (glass), but enables the input to this code to be provided in a novel way, via a user-generated diagram that is essentially a sketch of an arrival-time surface. We report on an implementation of this method, SpaghettiLens, which has been tested in a modelling challenge using 29 simulated lenses drawn from a larger set created for the Space Warps citizen science strong lens search. We find that volunteers from this online community asserted the image parities and time ordering consistently in some lenses, but made errors in other lenses depending on the image morphology. While errors in image parity and time ordering lead to large errors in the mass distribution, the enclosed mass was found to be more robust: the model-derived Einstein radii found by the volunteers were consistent with those produced by one of the professional team, suggesting that given the appropriate tools, gravitational lens modelling is a data analysis activity that can be crowd-sourced to good effect. Ideas for improvement are discussed, these include (a) overcoming the tendency of the models to be shallower than the correct answer in test cases, leading to systematic overestimation of the Einstein radius by 10 per cent at present, and (b) detailed modelling of arcs.

Light versus dark in strong-lens galaxies: dark matter haloes that are rounder than their stars

We measure the projected density profile, shape and alignment of the stellar and dark matter mass distribution in 11 strong-lens galaxies. We find that the projected dark matter density profile - under the assumption of a Chabrier stellar initial mass function - shows significant variation from galaxy to galaxy. Those with an outermost image beyond

Models of gravitational lens candidates from Space Warps CFHTLS

\sim 10

Weak microlensing: Weak microlensing

kpc are very well fit by a projected NFW profile; those with images within 10 kpc appear to be more concentrated than NFW, as expected if their dark haloes contract due to baryonic cooling. We find that over several half-light radii, the dark matter haloes of these lenses are rounder than their stellar mass distributions. While the haloes are never more elliptical than

Accurate analysis of Mg2+ binding to RNA: From classical methods to a novel iterative calculation procedure

e_{dm} = 0.2