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

Strong Lensing Analysis of the Galaxy Cluster MACS J1319.9+7003 and the Discovery of a Shell Galaxy

We present the first strong-lensing analysis of the massive galaxy cluster MACS J1319.9+7003 (z = 0:33, also known as Abell 1722), as part of our ongoing effort to analyze massive clusters with archival Hubble Space Telescope imaging. We identified and spectroscopically measured with Keck/MOSFIRE two galaxies multiply-imaged by the cluster. Our lensing analysis reveals a modest lens, with an effective Einstein radius of θe(z = 2) = 12"1, enclosing 2.1±0.3 x 10^(13) M_☉. We brie y discuss the strong-lensing properties of the cluster, using two different modeling techniques, and make the mass models publicly-availablea. Independently, we identifieed a noteworthy, young Shell Galaxy system forming around two likely interacting cluster members, 2000 north of the Brightest Cluster Galaxy (BCG), with the smaller companion only 0.66" (~3 kpc in projection) from the host galaxy's core. Shell galaxies are rare in galaxy clusters, and indeed, a simple estimate yields that they are only expected in roughly one in several dozen, to several hundred, massive galaxy clusters (the estimate can easily change by an order-of-magnitude within a reasonable range of characteristic values relevant for the calculation). While we assume the shell galaxy is in the cluster as is also evident from its colors, we also acknowledge that spectroscopic redshifts might be needed to further secure the nature of the system. Taking advantage of our lens model best-fit, mass-to-light scaling relation for cluster members, we infer that the total mass of the shell galaxy system is 1.3 x 10^(11) M_☉, with a host-to-companion mass ratio of about 10:1. Despite being rare in high density environments, the shell galaxy constitutes an example to how stars of cluster galaxies are being efficiently redistributed to the Intra Cluster Medium. Dedicated numerical simulations for the observed shell configuration, perhaps aided by the mass model, might cast interesting insight on the interaction history and properties of the two galaxies. An archival HST search in galaxy cluster images might reveal more such systems, whose rate would be interesting to compare to our estimate

Frontier Fields: High-Redshift Predictions and Early Results

The Frontier Fields program is obtaining deep Hubble and Spitzer Space Telescope images of new "blank" fields and nearby fields gravitationally lensed by massive galaxy clusters. The Hubble images of the lensed fields are revealing nJy sources (AB mag > 31), the faintest galaxies yet observed. In this paper, we present high-redshift (z > 6) number count predictions for the full program and candidates in three of the first Hubble Frontier Fields images. The full program will transform our understanding of galaxy evolution in the first 600 million years (z > 9). Where previous programs yielded perhaps a dozen z > 9 candidates, the Frontier Fields may yield ~70 (~6 per field). We base this estimate on an extrapolation of luminosity functions observed between 4 < z < 8 and gravitational lensing models submitted by the community. However, in the first two deep infrared Hubble images obtained to date, we find z ~ 8 candidates but no strong candidates at z > 9. This might suggest a deficit of faint z > 9 galaxies as also reported in the Ultra Deep Field (even while excesses of brighter z > 9 galaxies were reported in shallower fields). At these redshifts, cosmic variance (field-to-field variation) is expected to be significant (greater than +/-50%) and include clustering of early galaxies formed in overdensities. The full Frontier Fields program will significantly mitigate this uncertainty by observing six independent sightlines each with a lensing cluster and nearby blank field.Comment: Submitted for publication in the Astrophysical Journal. 15 pages, 17 figure

Hubble Space Telescope Combined Strong and Weak Lensing Analysis of the CLASH Sample: Mass and Magnification Models and Systematic Uncertainties

We present results from a comprehensive lensing analysis in Hubble Space Telescope (HST) data of the complete Cluster Lensing And Supernova survey with Hubble cluster sample. We identify previously undiscovered multiple images, allowing improved or first constraints on the cluster inner mass distributions and profiles. We combine these strong lensing constraints with weak lensing shape measurements within the HST field of view (FOV) to jointly constrain the mass distributions. The analysis is performed in two different common parameterizations (one adopts light-traces-mass for both galaxies and dark matter while the other adopts an analytical, elliptical Navarro-Frenk-White form for the dark matter) to provide a better assessment of the underlying systematics—which is most important for deep, cluster-lensing surveys, especially when studying magnified high-redshift objects. We find that the typical (median), relative systematic differences throughout the central FOV are ~40% in the (dimensionless) mass density, κ, and ~20% in the magnification, μ. We show maps of these differences for each cluster, as well as the mass distributions, critical curves, and two-dimensional (2D)-integrated mass profiles. For the Einstein radii (z_s = 2) we find that all typically agree within 10% between the two models, and Einstein masses agree, typically, within ~15%. At larger radii, the total projected, 2D-integrated mass profiles of the two models, within r ~ 2', differ by ~30%. Stacking the surface-density profiles of the sample from the two methods together, we obtain an average slope of dlog (Σ)/dlog (r) ~ –0.64 ± 0.1, in the radial range [5350] kpc. Last, we also characterize the behavior of the average magnification, surface density, and shear differences between the two models as a function of both the radius from the center and the best-fit values of these quantities. All mass models and magnification maps are made publicly available for the community

CLASH-VLT: Constraints on the Dark Matter Equation of State from Accurate Measurements of Galaxy Cluster Mass Profiles

A pressureless scenario for the dark matter (DM) fluid is a widely adopted hypothesis, despite the absence of direct observational evidence. According to general relativity, the total mass–energy content of a system shapes the gravitational potential well, but different test particles perceive this potential in different ways depending on their properties. Cluster galaxy velocities, being Ltc, depend solely on the gravitational potential, whereas photon trajectories reflect the contributions from the gravitational potential plus a relativistic-pressure term that depends on the cluster mass. We exploit this phenomenon to constrain the equation of state (EoS) parameter of the fluid, primarily DM, contained in galaxy clusters. We use complementary information provided by the kinematic and lensing mass profiles of the galaxy cluster MACS 1206.2−0847 at z = 0.44, as obtained in an extensive imaging and spectroscopic campaign within the Cluster Lensing And Supernova survey with Hubble. The unprecedented high quality of our data set and the properties of this cluster are well suited to determine the EoS parameter of the cluster fluid. Since baryons contribute at most 15% to the total mass in clusters and their pressure is negligible, the EoS parameter we derive describes the behavior of the DM fluid. We obtain the most stringent constraint on the DM EoS parameter to date, w = (pr + 2 pt)/(3 c^(2)ρ) = 0.00 ± 0.15 (stat) ± 0.08 (syst), averaged over the radial range 0.5 Mpc ≤ r ≤ r_200, where pr and pt are the radial and tangential pressure, and ρ is the density. We plan to further improve our constraint by applying the same procedure to all clusters from the ongoing Cluster Lensing And Supernova Survey with Hubble–Very Large Telescope program