1,101 research outputs found
Can the Steep Mass Profile of A1689 Be Explained by a Triaxial Dark Halo?
The steep mass profile of A1689 derived from recent detailed lensing
observations is not readily reconciled with the low concentration halos
predicted by the standard CDM model. However, halo triaxiality may act to bias
the profile constraints derived assuming a spherically symmetric mass
distribution, since lensing relates only to the projected mass distribution. A
degree of halo triaxiality is inherent to the CDM structure formation, arising
from the collision-less nature of the dark matter. Here we compare the
CDM-based model predictions of triaxial halo with the precise lensing
measurements of A1689 based on the ACS/HST and Subaru data, over a wide range
of 10kpc<r<2Mpc. The model lensing profiles cover the intrinsic spread of halo
mass and shape, and are projected over all inclinations when comparing with the
data. We show that the model parameters are only weakly constrained and
strongly degenerate mainly because of the lack of information along the line of
sight. In particular, the limits on the concentration parameter become less
restrictive with increasing triaxiality. Yet, by comparing the obtained
constraints with expected probability distributions for the axis ratio and
concentration parameters computed from numerical simulations, we find that ~6%
of cluster-size halos in the CDM model can match the A1689 lensing observations
at the 2-sigma level, corresponding to cases where the major-axis of the halo
is aligned with the line of sight. Thus halo triaxiality could reduce the
apparent discrepancy between theory and observation. This hypothesis needs to
be further explored by a statistical lensing study for other clusters as well
as by complementary three-dimensional information derived using X-ray,
kinematics, and SZ effect observations.Comment: 7 pages, 6 figures, accepted for publication in Ap
Asthma diagnosis and treatment - 1012. The efficacy of budesonide in the treatmetn of acute asthma in children: a double-blind, randomized, controlled trial.
Background
Current evidence suggests that inhaled glucocorticoids (IGC) have a more profound topical none genomic effect on bronchial airways as compared to systemic glucocorticoids. The value of adding IGC to current therapy of acute asthma is not well established.
Methods
We conducted a double-blind, randomized, two-arm, parallel groups, controlled clinical trial to compare the addition of budesonide 1500 mcg or placebo (normal saline) to standard acute asthma treatment (albuterol and ipratropium bromide) administered in 3 divided mixed doses within 1 hour in the emergency department (ED). Children 2-12 years of age with moderate or severe acute asthma, scoring 8-15/15 on a well-validated scoring system were included. Both groups received a single dose of prednisone 2 mg/kg/day (max. 60 mg) at the beginning of therapy. The primary outcome was admission rate within 2-4 hours from starting therapy.
Results
A total of 723 children were enrolled in the study over 17 months duration, of whom 139 were allowed to re-enroll and be randomized to constitute 906 randomization assignments (458 on the treatment group and 448 on the control group); with baseline mean + SD asthma score of 10.63 + 1.73; age 5.52 + 2.76 years; 35% girls; 30.8% (16.5%) with baseline severe asthma score of â„12 (â„ 13). Statistical Analysis plan allowed for the potential dependency in response due to reenrollments of a subset of children, using Generalized Linear Mixed Modeling (GLMM) techniques. Baseline demographic and clinical characteristics were not significantly different between the two randomized groups. Seventy-five out of 458 (16.4%) of the treatment group vs. 82/448 (18.3%) of the control group were admitted, (OR 0.85, CI: 0.59-1.23, p-value=0.39). Among the severe asthmatics with baseline score â„13, treatment vs. placebo group, GLMM adjusted admission rate was 30% vs. 47%, indicating a 17% difference in admission rate in favor of the treatment group (adjusted OR of 0.49, CI: 0.25-0.95; p-value= 0.035) that indicated a 51% reduction in the risk of admission for the treatment vs. control group.
Conclusions
Children with baseline severe asthma score â„13 who were treated with budesonide had a significant reduction in their admission rate
Gauge Theories in Noncommutative Homogeneous K\"ahler Manifolds
We construct a gauge theory on a noncommutative homogeneous K\"ahler
manifold, where we employ the deformation quantization with separation of
variables for K\"ahler manifolds formulated by Karabegov. A key point in this
construction is to obtaining vector fields which act as inner derivations for
the deformation quantization. We show that these vector fields are the only
Killing vector fields. We give an explicit construction of this gauge theory on
noncommutative and noncommutative .Comment: 27 pages, typos correcte
A Free-Form Lensing Grid Solution for A1689 with New Mutiple Images
Hubble Space Telescope imaging of the galaxy cluster Abell 1689 has revealed
an exceptional number of strongly lensed multiply-imaged galaxies, including
high-redshift candidates. Previous studies have used this data to obtain the
most detailed dark matter reconstructions of any galaxy cluster to date,
resolving substructures ~25 kpc across. We examine Abell 1689 (hereafter,
A1689) non-parametrically, combining strongly lensed images and weak
distortions from wider field Subaru imaging, and we incorporate member galaxies
to improve the lens solution. Strongly lensed galaxies are often locally
affected by member galaxies, however, these perturbations cannot be recovered
in grid based reconstructions because the lensing information is too sparse to
resolve member galaxies. By adding luminosity-scaled member galaxy deflections
to our smooth grid we can derive meaningful solutions with sufficient accuracy
to permit the identification of our own strongly lensed images, so our model
becomes self consistent. We identify 11 new multiply lensed system candidates
and clarify previously ambiguous cases, in the deepest optical and NIR data to
date from Hubble and Subaru. Our improved spatial resolution brings up new
features not seen when the weak and strong lensing effects are used separately,
including clumps and filamentary dark matter around the main halo. Our
treatment means we can obtain an objective mass ratio between the cluster and
galaxy components, for examining the extent of tidal stripping of the luminous
member galaxies. We find a typical mass-to-light ratios of M/L_B = 21 inside
the r<1 arcminute region that drops to M/L_B = 17 inside the r<40 arcsecond
region. Our model independence means we can objectively evaluate the
competitiveness of stacking cluster lenses for defining the geometric
lensing-distance-redshift relation in a model independent way.Comment: 23 pages with 25 figures Replced with MNRAS submitted version. Some
figures have been corrected and minor text edit
The Surprisingly Steep Mass Profile of Abell 1689, from a Lensing Analysis of Subaru Images
Subaru observations of A1689 (z=0.183) are used to derive an accurate,
model-independent mass profile for the entire cluster, r<2 Mpc/h, by combining
magnification bias and distortion measurements. The projected mass profile
steepens quickly with increasing radius, falling away to zero at r~1.0 Mpc/h,
well short of the anticipated virial radius. Our profile accurately matches
onto the inner profile, r<200 kpc/h, derived from deep HST/ACS images. The
combined ACS and Subaru information is well fitted by an NFW profile with
virial mass, (1.93 \pm 0.20)10^15 M_sun, and surprisingly high concentration,
c_vir=13.7^{+1.4}_{-1.1}, significantly larger than theoretically expected
(c_vir~4), corresponding to a relatively steep overall profile. A slightly
better fit is achieved with a steep power-law model that has its 2D logarithmic
slope -3 and core radius theta_c~1.7' (r_c~210 kpc/h), whereas an isothermal
profile is strongly rejected. These results are based on a reliable sample of
background galaxies selected to be redder than the cluster E/S0 sequence. By
including the faint blue galaxy population a much smaller distortion signal is
found, demonstrating that blue cluster members significantly dilute the true
signal for r~400 kpc/h. This contamination is likely to affect most weak
lensing results to date.Comment: 5 pages, 3 figures, to appear in ApJ
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
Searching dark-matter halos in the GaBoDS survey
We apply the linear filter for the weak-lensing signal of dark-matter halos
developed in Maturi et al. (2005) to the cosmic-shear data extracted from the
Garching-Bonn-Deep-Survey (GaBoDS). We wish to search for dark-matter halos
through weak-lensing signatures which are significantly above the random and
systematic noise level caused by intervening large-scale structures. We employ
a linear matched filter which maximises the signal-to-noise ratio by minimising
the number of spurious detections caused by the superposition of large-scale
structures (LSS). This is achieved by suppressing those spatial frequencies
dominated by the LSS contamination. We confirm the improved stability and
reliability of the detections achieved with our new filter compared to the
commonly-used aperture mass (Schneider, 1996; Schneider et al., 1998) and to
the aperture mass based on the shear profile expected for NFW haloes (see e.g.
Schirmer et al., 2004; Hennawi & Spergel, 2005). Schirmer et al.~(2006)
achieved results comparable to our filter, but probably only because of the low
average redshift of the background sources in GaBoDS, which keeps the LSS
contamination low. For deeper data, the difference will be more important, as
shown by Maturi et al. (2005). We detect fourteen halos on about eighteen
square degrees selected from the survey. Five are known clusters, two are
associated with over-densities of galaxies visible in the GaBoDS image, and
seven have no known optical or X-ray counterparts.Comment: 8 pages, 4 figures, accepted by A&
The Cluster Lensing and Supernova Survey with Hubble (CLASH): Strong Lensing Analysis of Abell 383 from 16-Band HST WFC3/ACS Imaging
We examine the inner mass distribution of the relaxed galaxy cluster Abell
383 in deep 16-band HST/ACS+WFC3 imaging taken as part of the CLASH multi-cycle
treasury program. Our program is designed to study the dark matter distribution
in 25 massive clusters, and balances depth with a wide wavelength coverage to
better identify lensed systems and generate precise photometric redshifts. This
information together with the predictive strength of our strong-lensing
analysis method identifies 13 new multiply-lensed images and candidates, so
that a total of 27 multiple-images of 9 systems are used to tightly constrain
the inner mass profile, (r<160 kpc).
We find consistency with the standard distance-redshift relation for the full
range spanned by the lensed images, 1.01<z<6.03, with the higher redshift
sources deflected through larger angles as expected. The inner mass profile
derived here is consistent with the results of our independent weak-lensing
analysis of wide-field Subaru images, with good agreement in the region of
overlap. The overall mass profile is well fitted by an NFW profile with
M_{vir}=(5.37^{+0.70}_{-0.63}\pm 0.26) x 10^{14}M_{\odot}/h and a relatively
high concentration, c_{vir}=8.77^{+0.44}_{-0.42}\pm 0.23, which lies above the
standard c-M relation similar to other well-studied clusters. The critical
radius of Abell 383 is modest by the standards of other lensing clusters,
r_{E}\simeq16\pm2\arcsec (for z_s=2.55), so the relatively large number of
lensed images uncovered here with precise photometric redshifts validates our
imaging strategy for the CLASH survey. In total we aim to provide similarly
high-quality lensing data for 25 clusters, 20 of which are X-ray selected
relaxed clusters, enabling a precise determination of the representative mass
profile free from lensing bias. (ABRIDGED)Comment: 15 pages, 14 figures, 2 tabels; V3 matches the submitted version
later published in Ap
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