Strong Lensing Analysis of the Powerful Lensing Cluster MACS J2135.2-0102 (zz=0.33)

We present a light-traces-mass (LTM) strong-lensing model of the massive lensing cluster MACS J2135.2-0102 ($z$=0.33; hereafter MACS2135), known in part for hosting the Cosmic Eye galaxy lens. MACS2135 is also known to multiply-lens a $z=$2.3 sub-mm galaxy near the Brightest Cluster Galaxy (BCG), as well as a prominent, triply-imaged system at a large radius of $\sim$37" south of the BCG. We use the latest available Hubble imaging to construct an accurate lensing model for this cluster, identifying six new multiply-imaged systems with the guidance of our LTM method, so that we have roughly quadrupled the number of lensing constraints. We determine that MACS2135 is amongst the top lensing clusters known, comparable in size to the Hubble Frontier Fields. For a source at $z_{s}=2.32$, we find an effective Einstein radius of $\theta_{e}=27\pm3$", enclosing $1.12 \pm0.16 \times10^{14}$ $M_{\odot}$. We make our lens model, including mass and magnification maps, publicly available, in anticipation of searches for high-$z$ galaxies with the James Webb Space Telescope for which this cluster is a compelling target.Comment: 7 pages, 2 figures (3 subfigures in total), 1 table; Published in ApJ; V2: accepted versio

Multi-Phenomena Modeling of the New Bullet Cluster, ZwCl008.8+52, using N-body/hydrodynamical Simulations

We use hydrodynamical/N-body simulations to interpret the newly discovered Bullet-cluster-like merging cluster, ZwCl 0008.8+5215 (ZwCl 0008 hereafter), where a dramatic collision is apparent from multi-wavelength observations. We have been able to find a self-consistent solution for the radio, X-ray, and lensing phenomena by projecting an off-axis, binary cluster encounter viewed just after first core passage. A pair radio relics traces well the leading and trailing shock fronts that our simulation predict, providing constraints on the collision parameters. We can also account for the observed distinctive comet-like X-ray morphology and the positions of the X-ray peaks relative to the two lensing mass centroids and the two shock front locations. Relative to the Bullet cluster, the total mass is about 70% lower, ($1.2\pm0.1) \times 10^{15}$ Msun, with a correspondingly lower infall velocity, $1800\pm300$ km/s, and an impact parameter of $400\pm100$ kpc. As a result, the gas component of the infalling cluster is not trailing significantly behind the associated dark matter as in the case of the Bullet cluster. The degree of agreement we find between all the observables provides strong evidence that dark matter is effectively collisionless on large scales calling into question other claims and theories that advocate modified gravity.Comment: 9 pages, 3 figures, and 1 table, submitted to the Astrophysical Journal for publicationon on December 18. Coments are welcom

Mass Distributions of Clusters Using Gravitational Magnification

Lensing in the context of rich clusters is normally quantified from small image distortions, yielding a relative mass distribution in the limit of weak lensing. Here we show the magnification effect of lensing can also be mapped over a cluster, resulting in absolute mass determinations for the weak limit. Furthermore, given both magnification and distortion measurements, the mass distribution may be constrained in the strong regime. Methods for obtaining the magnification using spectroscopic and/or photometric information are discussed, for object detection within a fixed isophote or to a given flux limit. A map of the magnification around A1689 is constructed from the observed depletion of background red galaxy counts.Comment: 10 pages uuencoded, compressed, figures included. Invited Review, proc of 5th Maryland Dark Matter Oct. 9

Cloning Dropouts: Implications for Galaxy Evolution at High Redshift

The evolution of high redshift galaxies in the two Hubble Deep Fields, HDF-N and HDF-S, is investigated using a cloning technique that replicates z~ 2-3 U dropouts to higher redshifts, allowing a comparison with the observed B and V dropouts at higher redshifts (z ~ 4-5). We treat each galaxy selected for replication as a set of pixels that are k-corrected to higher redshift, accounting for resampling, shot-noise, surface-brightness dimming, and the cosmological model. We find evidence for size evolution (a 1.7x increase) from z ~ 5 to z ~ 2.7 for flat geometries (Omega_M+Omega_LAMBDA=1.0). Simple scaling laws for this cosmology predict that size evolution goes as (1+z)^{-1}, consistent with our result. The UV luminosity density shows a similar increase (1.85x) from z ~ 5 to z ~ 2.7, with minimal evolution in the distribution of intrinsic colors for the dropout population. In general, these results indicate less evolution than was previously reported, and therefore a higher luminosity density at z ~ 4-5 (~ 50% higher) than other estimates. We argue the present technique is the preferred way to understand evolution across samples with differing selection functions, the most relevant differences here being the color cuts and surface brightness thresholds (e.g., due to the (1+z)^4 cosmic surface brightness dimming effect).Comment: 56 pages, 22 figures, accepted for publication in Ap