Strong‐Lensing Analysis of A1689 from Deep Advanced Camera Images

Abstract

We analyze deep multicolor Advanced Camera images of the largest known gravitational lens, A1689. Radial and tangential arcs delineate the critical curves in unprecedented detail, and many small counterimages are found near the center of mass. We construct a flexible light deflection field to predict the appearance and positions of counterimages. The model is refined as new counterimages are identified and incorporated to improve the model, yielding a total of 106 images of 30 multiply lensed background galaxies, spanning a wide redshift range, 1:0 < z < 5:5. The resulting mass map is more circular in projection than the clumpy distribution of cluster galaxies, and the light is more concentrated than the mass within r < 50 kpc h À1 . The projected mass profile flattens steadily toward the center with a shallow mean slope of dlog AE=dlog r ' À0:55 AE 0:1, over the observed range r < 250 kpc h À1 , matching well an NFW profile, but with a relatively high concentration, C vir ¼ 8:2 þ2:1 À1:8 . A softened isothermal profile (r core ¼ 20 AE 2 00 ) is not conclusively excluded, illustrating that lensing constrains only projected quantities. Regarding cosmology, we clearly detect the purely geometric increase of bend angles with redshift. The dependence on the cosmological parameters is weak owing to the proximity of A1689, z ¼ 0:18, constraining the locus, M þ Ã 1:2. This consistency with standard cosmology provides independent support for our model, because the redshift information is not required to derive an accurate mass map. Similarly, the relative fluxes of the multiple images are reproduced well by our best-fitting lens model.

Mass and magnification maps for the Hubble Space Telescope Frontier Fields clusters: implications for high-redshift studies

“…The unparalleled power of Hubble Space Telescope (HST) for such studies is exemplified by the identification of 42 multiple-image systems in Advanced Camera for Surveys (ACS) observations of the massive cluster Abell 1689 (Broadhurst et al 2005), 24 of them with measured redshifts from deep Keck and VLT spectroscopy ). The ability to obtain spectra for gravitationally amplified galaxies at high redshift is a critical advantage over similar work conducted on non-magnified galaxies in the field, and crucial for the exploration of the end of the Dark Ages, one of the most ambitious and timely quests of present-day astrophysics.…”

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

“…is a Light Traces Mass (LTM) method, so that both the galaxies and the dark matter follow the light distribution. The method is described in detail by Zitrin et al ( , 2013, and it is inspired by the LTM assumptions outlined by Broadhurst et al (2005). The model consists of two main components.…”

Sn Refsdal: Photometry and Time Delay Measurements of the First Einstein Cross Supernova

“…The presentation of the SN Refsdal discovery by Kelly et al (2015c) included a first analysis of the SN lensing, using the "light traces mass" (LTM) modeling approach (Broadhurst et al 2005;). Within a week of the initial announcement, two other teams produced revised strong lensing models for the MACS J1149.6+2223 cluster (Oguri 2015;Sharon & Johnson 2015).…”