7,526 research outputs found
First Weak-lensing Results from "See Change": Quantifying Dark Matter in the Two Z>1.5 High-redshift Galaxy Clusters SPT-CL J2040-4451 and IDCS J1426+3508
We present a weak-lensing study of SPT-CLJ2040-4451 and IDCSJ1426+3508 at
z=1.48 and 1.75, respectively. The two clusters were observed in our "See
Change" program, a HST survey of 12 massive high-redshift clusters aimed at
high-z supernova measurements and weak-lensing estimation of accurate cluster
masses. We detect weak but significant galaxy shape distortions using IR images
from the WFC3, which has not yet been used for weak-lensing studies. Both
clusters appear to possess relaxed morphology in projected mass distribution,
and their mass centroids agree nicely with those defined by both the galaxy
luminosity and X-ray emission. Using an NFW profile, for which we assume that
the mass is tightly correlated with the concentration parameter, we determine
the masses of SPT-CL J2040-4451 and IDCS J1426+3508 to be
M_{200}=8.6_{-1.4}^{+1.7}x10^14 M_sun and 2.2_{-0.7}^{+1.1}x10^14 M_sun,
respectively. The weak-lensing mass of SPT-CLJ2040-4451 shows that the cluster
is clearly a rare object. Adopting the central value, the expected abundance of
such a massive cluster at z>1.48 is only ~0.07 in the parent 2500 sq. deg.
survey. However, it is yet premature to claim that the presence of this cluster
creates a serious tension with the current LCDM paradigm unless that tension
will remain in future studies after marginalizing over many sources of
uncertainties such as the accuracy of the mass function and the
mass-concentration relation at the high mass end. The mass of IDCSJ1426+3508 is
in excellent agreement with our previous ACS-based weak-lensing result while
the much higher source density from our WFC3 imaging data makes the current
statistical uncertainty ~40% smaller.Comment: Accepted to Ap
Robust eye tracking based on multiple corneal reflections for clinical applications
Postprint (published version
CLASH: Weak-Lensing Shear-and-Magnification Analysis of 20 Galaxy Clusters
We present a joint shear-and-magnification weak-lensing analysis of a sample
of 16 X-ray-regular and 4 high-magnification galaxy clusters at 0.19<z<0.69
selected from the Cluster Lensing And Supernova survey with Hubble (CLASH). Our
analysis uses wide-field multi-color imaging, taken primarily with Suprime-Cam
on the Subaru Telescope. From a stacked shear-only analysis of the
X-ray-selected subsample, we detect the ensemble-averaged lensing signal with a
total signal-to-noise ratio of ~25 in the radial range of 200 to 3500kpc/h. The
stacked tangential-shear signal is well described by a family of standard
density profiles predicted for dark-matter-dominated halos in gravitational
equilibrium, namely the Navarro-Frenk-White (NFW), truncated variants of NFW,
and Einasto models. For the NFW model, we measure a mean concentration of
at . We show this is in excellent agreement with Lambda
cold-dark-matter (LCDM) predictions when the CLASH X-ray selection function and
projection effects are taken into account. The best-fit Einasto shape parameter
is , which is consistent with the
NFW-equivalent Einasto parameter of . We reconstruct projected mass
density profiles of all CLASH clusters from a joint likelihood analysis of
shear-and-magnification data, and measure cluster masses at several
characteristic radii. We also derive an ensemble-averaged total projected mass
profile of the X-ray-selected subsample by stacking their individual mass
profiles. The stacked total mass profile, constrained by the
shear+magnification data, is shown to be consistent with our shear-based
halo-model predictions including the effects of surrounding large-scale
structure as a two-halo term, establishing further consistency in the context
of the LCDM model.Comment: Accepted by ApJ on 11 August 2014. Textual changes to improve clarity
(e.g., Sec.3.2.2 "Number-count Depletion", Sec.4.3 "Shape Measurement",
Sec.4.4 "Background Galaxy Selection"). Results and conclusions remain
unchanged. For the public release of Subaru data, see
http://archive.stsci.edu/prepds/clash
Three-dimensional Multi-probe Analysis of the Galaxy Cluster A1689
We perform a 3D multi-probe analysis of the rich galaxy cluster A1689 by
combining improved weak-lensing data from new BVRi'z' Subaru/Suprime-Cam
observations with strong-lensing, X-ray, and Sunyaev-Zel'dovich effect (SZE)
data sets. We reconstruct the projected matter distribution from a joint
weak-lensing analysis of 2D shear and azimuthally integrated magnification
constraints, the combination of which allows us to break the mass-sheet
degeneracy. The resulting mass distribution reveals elongation with axis ratio
~0.7 in projection. When assuming a spherical halo, our full weak-lensing
analysis yields a projected concentration of
(), consistent with and improved from earlier weak-lensing
work. We find excellent consistency between weak and strong lensing in the
region of overlap. In a parametric triaxial framework, we constrain the
intrinsic structure and geometry of the matter and gas distributions, by
combining weak/strong lensing and X-ray/SZE data with minimal geometric
assumptions. We show that the data favor a triaxial geometry with minor-major
axis ratio 0.39+/-0.15 and major axis closely aligned with the line of sight
(22+/-10 deg). We obtain and
, which overlaps with the tail of the predicted
distribution. The shape of the gas is rounder than the underlying matter but
quite elongated with minor-major axis ratio 0.60+/-0.14. The gas mass fraction
within 0.9Mpc is 10^{+3}_{-2}%. The thermal gas pressure contributes to ~60% of
the equilibrium pressure, indicating a significant level of non-thermal
pressure support. When compared to Planck's hydrostatic mass estimate, our
lensing measurements yield a spherical mass ratio of and with and without corrections for lensing projection
effects, respectively.Comment: Accepted by ApJ. Minor textual changes to improve clarity (e.g., 5.
HST STRONG-LENSING ANALYSIS). 26 pages, 17 figures. A version with
high-resolution figures is available at
http://www.asiaa.sinica.edu.tw/~keiichi/upfiles/Umetsu15/umetsu15.pd
Source Selection for Cluster Weak Lensing Measurements in the Hyper Suprime-Cam Survey
We present optimized source galaxy selection schemes for measuring cluster
weak lensing (WL) mass profiles unaffected by cluster member dilution from the
Subaru Hyper Suprime-Cam Strategic Survey Program (HSC-SSP). The ongoing
HSC-SSP survey will uncover thousands of galaxy clusters to . In
deriving cluster masses via WL, a critical source of systematics is
contamination and dilution of the lensing signal by cluster {members, and by
foreground galaxies whose photometric redshifts are biased}. Using the
first-year CAMIRA catalog of 900 clusters with richness larger than 20
found in 140 deg of HSC-SSP data, we devise and compare several
source selection methods, including selection in color-color space (CC-cut),
and selection of robust photometric redshifts by applying constraints on their
cumulative probability distribution function (PDF; P-cut). We examine the
dependence of the contamination on the chosen limits adopted for each method.
Using the proper limits, these methods give mass profiles with minimal dilution
in agreement with one another. We find that not adopting either the CC-cut or
P-cut methods results in an underestimation of the total cluster mass
() and the concentration of the profile (). The level of
cluster contamination can reach as high as at
Mpc/ for low-z clusters without cuts, while employing either the P-cut or
CC-cut results in cluster contamination consistent with zero to within the 0.5%
uncertainties. Our robust methods yield a detection of the
stacked CAMIRA surface mass density profile, with a mean mass of
.Comment: 19 pages, 4 tables, 12 figures, accepted to PASJ special issu
The mass distribution in an assembling super galaxy group at
We present a weak gravitational lensing analysis of supergroup SG11201202,
consisting of four distinct X-ray-luminous groups, that will merge to form a
cluster comparable in mass to Coma at . These groups lie within a
projected separation of 1 to 4 Mpc and within km s and
form a unique protocluster to study the matter distribution in a coalescing
system.
Using high-resolution {\em HST}/ACS imaging, combined with an extensive
spectroscopic and imaging data set, we study the weak gravitational distortion
of background galaxy images by the matter distribution in the supergroup. We
compare the reconstructed projected density field with the distribution of
galaxies and hot X-ray emitting gas in the system and derive halo parameters
for the individual density peaks.
We show that the projected mass distribution closely follows the locations of
the X-ray peaks and associated brightest group galaxies. One of the groups that
lies at slightly lower redshift () than the other three groups
() is X-ray luminous, but is barely detected in the
gravitational lensing signal. The other three groups show a significant
detection (up to in mass), with velocity dispersions between
and km s and masses between
and , consistent with independent measurements. These groups are
associated with peaks in the galaxy and gas density in a relatively
straightforward manner. Since the groups show no visible signs of interaction,
this supports the picture that we are catching the groups before they merge
into a cluster.Comment: 10 pages, 10 figures, accepted for publication by Astronomy &
Astrophysic
CLASH: Mass Distribution in and around MACS J1206.2-0847 from a Full Cluster Lensing Analysis
We derive an accurate mass distribution of the galaxy cluster MACS
J1206.2-0847 (z=0.439) from a combined weak-lensing distortion, magnification,
and strong-lensing analysis of wide-field Subaru BVRIz' imaging and our recent
16-band Hubble Space Telescope observations taken as part of the Cluster
Lensing And Supernova survey with Hubble (CLASH) program. We find good
agreement in the regions of overlap between several weak and strong lensing
mass reconstructions using a wide variety of modeling methods, ensuring
consistency. The Subaru data reveal the presence of a surrounding large scale
structure with the major axis running approximately north-west south-east
(NW-SE), aligned with the cluster and its brightest galaxy shapes, showing
elongation with a \sim 2:1 axis ratio in the plane of the sky. Our full-lensing
mass profile exhibits a shallow profile slope dln\Sigma/dlnR\sim -1 at cluster
outskirts (R>1Mpc/h), whereas the mass distribution excluding the NW-SE excess
regions steepens further out, well described by the Navarro-Frenk-White form.
Assuming a spherical halo, we obtain a virial mass M_{vir}=(1.1\pm 0.2\pm
0.1)\times 10^{15} M_{sun}/h and a halo concentration c_{vir} = 6.9\pm 1.0\pm
1.2 (\sim 5.7 when the central 50kpc/h is excluded), which falls in the range
4 <7 of average c(M,z) predictions for relaxed clusters from recent Lambda
cold dark matter simulations. Our full lensing results are found to be in
agreement with X-ray mass measurements where the data overlap, and when
combined with Chandra gas mass measurements, yield a cumulative gas mass
fraction of 13.7^{+4.5}_{-3.0}% at 0.7Mpc/h (\approx 1.7r_{2500}), a typical
value observed for high mass clusters.Comment: Accepted by ApJ (30 pages, 17 figures), one new figure (Figure 10)
added, minor text changes; a version with high resolution figures available
at http://www.asiaa.sinica.edu.tw/~keiichi/upfiles/MACS1206/ms_highreso.pd
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