148 research outputs found
Weak lensing detection of intra-cluster filaments with ground based data
According to the current standard model of Cosmology, matter in the Universe
arranges itself along a network of filamentary structure. These filaments
connect the main nodes of this so-called 'Cosmic Web', which are clusters of
galaxies. Although its large-scale distribution is clearly characterized by
numerical simulations, constraining the dark matter content of the cosmic web
in reality turns out to be difficult. The natural method of choice is
gravitational lensing. However, the direct detection and mapping of the elusive
filament signal is challenging and in this work we present two
methods,specifically tailored to achieve this task. A linear matched filter
aims at the detection of the smooth mass component of filaments and is
optimized to perform a shear decomposition that follows the anisotropic
component of the lensing signal. Filaments clearly inherit this property due to
their morphology. At the same time, the contamination arising from the central
massive cluster is controlled in a natural way. The filament 1 {\sigma}
detection is of about {\kappa} ~ 0.01-0.005 according to the filter's template
width and length, enabling the detection of structures out of reach with other
approaches. The second, complementary method seeks to detect the clumpy
component of filaments. The detection is determined by the number density of
sub-clump identifications in an area enclosing the potential filament, as it
was found within the observed field with the filter approach. We test both
methods against Mock observations based on realistic N-Body simulations of
filamentary structure and prove the feasibility of detecting filaments with
ground-based data.Comment: 9 pages, 7 figures. Submitted to A&A. Comments very welcom
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
Gravitational lensing : an advanced method to recover the mass distribution of galaxy clusters
Die vorliegende Arbeit beschäftigt sich mit Galaxienhaufen. Diese massereichsten, gravitativ gebundenen Objekte im beobachtbaren Universum repräsentieren das obere Ende der Massenfunktion und sind von speziellem Interesse für die Kosmologie. Nicht nur lassen sich mehrere kosmologische Parameter aus der Beobachtung und vor allem aus der Massenbestimmung von Galaxienhaufen ableiten, sie stellen auch ideale kosmische Laboratorien dar, welche einen direkten Vergleich zwischen Beobachtung und numerischer Simulation erlauben. Die vielleicht vielversprechendste Methode um die Eigenschaften von Galaxienhaufen zu ermitteln ist der Gravitationslinseneffekt. Das Licht entfernter Hintergrundgalaxien wird aufgrund der hohen Massekonzentration in einem Galaxienhaufen auf dem Weg zum Beobachter abgelenkt und trägt daher Informationen über den Deflektor. In dieser Arbeit entwickeln wir eine neue, moderne Methode welche den sogenannten starken und schwachen Gravitationslinseneffekt optimal kombiniert und daher eine nichtparametrische Rekonstruktion der Massenverteilung des Deflektors erlaubt. Diese Methode ist in einem fortschrittlichen numerischen Algorithmus implementiert, welcher effiziente numerische Verfahren und parallele Höchstleistungs-Computersysteme ausnutzt. Mit Rekonstruktionen numerisch simulierter Galaxienhaufen zeigen wir die Leistungsfähigkeit unserer Methode, im Vergleich mit etablierten Techniken. Wir schließen unsere Arbeit mit Rekonstruktion und Analyse von MS2137.3-2353 und CL0024+1654, zweier wohlbekannter Galaxienhaufen die spektakuläre Phänomene des starken Gravitationslinseneffektes aufweisen
Multiple Images of a Highly Magnified Supernova Formed by an Early-Type Cluster Galaxy Lens
In 1964, Refsdal hypothesized that a supernova whose light traversed multiple paths around a strong gravitational lens could be used to measure the rate of cosmic expansion. We report the discovery of such a system. In Hubble Space Telescope imaging, we have found four images of a single supernova forming an Einstein cross configuration around a redshift z = 0.54 elliptical galaxy in the MACS J1149.6+2223 cluster. The cluster’s gravitational potential also creates multiple images of the z = 1.49 spiral supernova host galaxy, and a future appearance of the supernova elsewhere in the cluster field is expected. The magnifications and staggered arrivals of the supernova images probe the cosmic expansion rate, as well as the distribution of matter in the galaxy and cluster lenses
Joint cluster reconstructions: Combining free-form lensing and X-rays
Galaxy clusters provide a multitude of observational data across wavelengths
and their structure and morphology are of considerable interest in cosmology as
well as astrophysics. We develop a framework that allows the combination of
lensing and non-lensing observations in a free-form and mesh-free approach to
infer the projected mass distribution of individual galaxy clusters. This
method can be used to test common assumptions on the morphology of clusters in
parametric models. We make use of the lensing reconstruction code SaWLens2 and
expand its capabilities by incorporating an estimate of the projected
gravitational potential based on X-ray data that are deprojected using the
local Richardson-Lucy method and used to infer the Newtonian potential of the
cluster and we discuss how potentially arising numerical artefacts can be
treated. We demonstrate the feasibility of our method on a simplified mock NFW
halo and on a cluster from a realistic hydrodynamical simulation and show how
the combination of X-ray and weak lensing data can affect a free-form
reconstruction, improving the accuracy in the central region in some cases by a
factor of two.Comment: 14 pages, 19 figures, submitted to A&A; revised to match the accepted
versio
CLASH: Joint Analysis of Strong-Lensing, Weak-Lensing Shear and Magnification Data for 20 Galaxy Clusters
We present a comprehensive analysis of strong-lensing, weak-lensing shear and magnification data for a sample of 16 X-ray-regular and 4 high-magnification galaxy clusters at 0.19 ≾ z ≾ 0.69 selected from Cluster Lensing And Supernova survey with Hubble (CLASH). Our analysis combines constraints from 16-band Hubble Space Telescope observations and wide-field multi-color imaging taken primarily with Suprime-Cam on the Subaru Telescope, spanning a wide range of cluster radii (10"–16'). We reconstruct surface mass density profiles of individual clusters from a joint analysis of the full lensing constraints, and determine masses and concentrations for all of the clusters. We find the internal consistency of the ensemble mass calibration to be ≤5% ± 6% in the one-halo regime (200–2000 kpc h−1) compared to the CLASH weak-lensing-only measurements of Umetsu et al. For the X-ray-selected subsample of 16 clusters, we examine the concentration–mass (c–M) relation and its intrinsic scatter using a Bayesian regression approach. Our model yields a mean concentration of c|_z=0.34 =3.95 ± 0.35 at M_(200c) ≃ 14 × 10^(14) M_⊙ and an intrinsic scatter of σ(ln c_(200c) = 0.13 ± 0.06, which is in excellent agreement with Λ cold dark matter predictions when the CLASH selection function based on X-ray morphological regularity and the projection effects are taken into account. We also derive an ensemble-averaged surface mass density profile for the X-ray-selected subsample by stacking their individual profiles. The stacked lensing signal is detected at 33σ significance over the entire radial range ≤4000 kpc h^(−1), accounting for the effects of intrinsic profile variations and uncorrelated large-scale structure along the line of sight. The stacked mass profile is well described by a family of density profiles predicted for cuspy dark-matter-dominated halos in gravitational equilibrium, namely, the Navarro–Frenk–White (NFW), Einasto, and DARKexp models, whereas the single power-law, cored isothermal and Burkert density profiles are disfavored by the data. We show that cuspy halo models that include the large-scale two-halo term provide improved agreement with the data. For the NFW halo model, we measure a mean concentration of c_(200c) = 3.79_(-0.28)^(+0.30) at M_(200c) 14.1_(-1.0)^(+1.0) x 10^(14) M_☉, demonstrating consistency between the complementary analysis methods
A Comparison and Joint Analysis of Sunyaev-Zel'dovich Effect Measurements from Planck and Bolocam for a set of 47 Massive Galaxy Clusters
We measure the SZ signal toward a set of 47 clusters with a median mass of
M and a median redshift of 0.40 using data from
Planck and the ground-based Bolocam receiver. When Planck XMM-like masses are
used to set the scale radius , we find consistency between
the integrated SZ signal, , derived from Bolocam and Planck
based on gNFW model fits using A10 shape parameters, with an average ratio of
(allowing for the % Bolocam flux calibration
uncertainty). We also perform a joint fit to the Bolocam and Planck data using
a modified A10 model with the outer logarithmic slope allowed to vary,
finding (measurement error followed by
intrinsic scatter). In addition, we find that the value of scales with
mass and redshift according to . This mass scaling is in good agreement with recent
simulations. We do not observe the strong trend of with redshift seen
in simulations, though we conclude that this is most likely due to our sample
selection. Finally, we use Bolocam measurements of to test the
accuracy of the Planck completeness estimate. We find consistency, with the
actual number of Planck detections falling approximately below the
expectation from Bolocam. We translate this small difference into a constraint
on the the effective mass bias for the Planck cluster cosmology results, with
.Comment: Updated to include one additional co-author. Also some minor changes
to the text based on initial feedbac
CLUMP-3D: three-dimensional lensing and multi-probe analysis of MACS J1206.2−0847, a remarkably regular cluster
Multi-wavelength techniques can probe the distribution and the physical properties of baryons and dark matter in galaxy clusters from the inner regions out to the peripheries. We present a full three-dimensional analysis combining strong and weak lensing, X-ray surface brightness and temperature, and the Sunyaev–Zel'dovich effect. The method is applied to MACS J1206.2−0847, a remarkably regular, face-on, massive, M_(200) = (1.1 ± 0.2) × 10^(15) M⊙ h^(−1), cluster at z = 0.44. The measured concentration, c_(200) = 6.3 ± 1.2, and the triaxial shape are common to haloes formed in a Λ cold dark matter scenario. The gas has settled in and follows the shape of the gravitational potential, which is evidence of pressure equilibrium via the shape theorem. There is no evidence for significant non-thermal pressure and the equilibrium is hydrostatic
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