Combined reconstruction of weak and strong lensing data with WSLAP

et al. 2016

ApJ

Self Cite

108

161

Supernova "Refsdal," multiply imaged by cluster MACS1149.5+2223, represents a rare opportunity to make a true blind test of model predictions in extragalactic astronomy, on a timescale that is short compared to a human lifetime. In order to take advantage of this event, we produced seven gravitational lens models with five independent methods, based on Hubble Space Telescope (HST) Hubble Frontier Field images, along with extensive spectroscopic follow-up observations by HST, the Very Large and the Keck Telescopes. We compare the model predictions and show that they agree reasonably well with the measured time delays and magnification ratios between the known images, even though these quantities were not used as input. This agreement is encouraging, considering that the models only provide statistical uncertainties, and do not include additional sources of uncertainties such as structure along the line of sight, cosmology, and the mass sheet degeneracy. We then present the model predictions for the other appearances of supernova "Refsdal." A future image will reach its peak in the first half of 2016, while another image appeared between 1994 and 2004. The past image would have been too faint to be detected in existing archival images. The future image should be approximately one-third as bright as the brightest known image (i.e., H 25.7 AB » mag at peak and H 26.7 AB » mag six months before peak), and thus detectable in single-orbit HST images. We will find out soon whether our predictions are correct.

Section: Diego Et Almentioning

confidence: 99%

“Refsdal” Meets Popper: Comparing Predictions of the Re-Appearance of the Multiply Imaged Supernova Behind MACSJ1149.5+2223

Treu

Brammer

et al. 2016

ApJ

Self Cite

108

161

“…The reader can find the details of the method in our previous papers (Diego et al 2005a(Diego et al , 2007(Diego et al , 2016Sendra et al 2014). Here we give a brief summary of the most essential elements.…”

Section: Lensing Reconstruction Algorithm; Wslap+mentioning

confidence: 99%

“…This elongation extends well beyond the virial radius of the cluster (Gruen et al 2013), but with an azimuthally averaged large scale massive profile that fits well the NFW form out to a radius of 2 Mpc/h (Umetsu et al 2015). In this paper, we make a strong lensing analysis of the deep new optical HFF data now completed for this cluster, using our general free-form lensing technique (Diego et al 2005a(Diego et al , 2007(Diego et al , 2016Sendra et al 2014). Our aim is to objectively identify new multiply lensed systems for understanding the properties of low luminosity galaxies in the high redshift Universe.…”

Section: Introductionmentioning

confidence: 99%

A free-form mass model of the Hubble Frontier Fields cluster AS1063 (RXC J2248.7−4431) with over one hundred constraints

Mon. Not. R. Astron. Soc.

Broadhurst

Wong

et al. 2016

We derive a free-form mass distribution for the massive cluster AS1063 (z=0.348) using the completed optical imaging from the Hubble Frontier Fields programme. Based on a subset of 11 multiply lensed systems with spectroscopic redshift we produce a lens model that is accurate enough to unveil new multiply lensed systems, totalling over a 100 arclets, and to estimate their redshifts geometrically. Consistency is found between this precise model and that obtained using only the subset of lensed sources with spectroscopically measured redshifts.Although a relatively large elongation of the mass distribution is apparent relative to the X-ray map, no significant offset is found between the centroid of our mass distribution and that of the X-ray emission map, suggesting a relatively relaxed state for this cluster. For the well resolved lensed images we provide detailed model comparisons to illustrate the precision of our model and hence the reliability of our de-lensed sources. A clear linear structure is associated with one such source extending 23 kpc in length, that could be an example of jet-induced star formation, at redshift z ≈ 3.1.

“…As discussed in Diego et al (2007), this residual can be described (to first order) by a Gaussian distribution with a diagonal covariance matrix. This is however an approximation.…”

Section: Inversion Of the Lens Equationmentioning

confidence: 99%

“…On the positive side, in cases where the number of constraints is large, the results obtained with the parametric and non-parametric methods agree well (Diego et al 2005b) probing, among other things, that the dark matter does trace the luminous matter and the usefulness of non-parametric methods as a way of testing that the assumptions made in the parametric methods are well founded. Non-parametric methods have been used as well to combine weak and strong lensing data in the same analysis (Abdelsalam et al 1998b;Bridle et al 1998;Saha et al 1999;Kneib et al 2003;Smith et al 2005;Bradač et al 2005;Diego et al 2007). …”

Section: Introductionmentioning

confidence: 99%

Systematics in lensing reconstruction: dark matter rings in the sky?

Ponente

2011

A&A

Self Cite

Context. Non-parametric lensing methods are a useful way of reconstructing the lensing mass of a cluster without making assumptions about the way the mass is distributed in the cluster. These methods are particularly powerful in the case of galaxy clusters with a large number of constraints. The advantage of not assuming implicitly that the luminous matter follows the dark matter is particularly interesting in those cases where the cluster is in a non-relaxed dynamical state. On the other hand, non-parametric methods have several limitations that should be taken into account carefully. Aims. We explore some of these limitations and focus on their implications for the possible ring of dark matter around the galaxy cluster CL0024+17. Methods. We project three background galaxies through a mock cluster of known radial profile density and obtain a map for the arcs (θ map). We also calculate the shear field associated with the mock cluster across the whole field of view (3.3 arcmin). Combining the positions of the arcs and the two-direction shear, we perform an inversion of the lens equation using two separate methods, the biconjugate gradient, and the quadratic programming (QADP) to reconstruct the convergence map of the mock cluster. Results. We explore the space of the solutions of the convergence map and compare the radial density profiles to the density profile of the mock cluster. When the inversion matrix algorithms are forced to find the exact solution, we encounter systematic effects resembling ring structures, that clearly depart from the original convergence map. Conclusions. Overfitting lensing data with a non-parametric method can produce ring-like structures similar to the alleged one in CL0024.