1,254 research outputs found
Detection of weak lensing by a cluster of galaxies at z=0.83
We report the detection of weak gravitational lensing of faint, distant
background galaxies by the rich, X-ray luminous cluster of galaxies MS1054-03
at z=0.83. This is the first measurement of weak lensing by a bona fide cluster
at such a high redshift. We detect tangential shear at the 5% - 10% level over
a range of radii 50'' < r < 250'' centered on the optical position of the
cluster. Two-dimensional mass reconstruction using galaxies with 21.5 < I <
25.5 shows a strong peak which coincides with the peak of the smoothed cluster
light distribution. Splitting this sample by magnitude (at I = 23.5) and color
(at R-I = 0.7), we find that the brighter and redder subsamples are only very
weakly distorted, indicating that the faint blue galaxies (FBG's), which
dominate the shear signal, are relatively more distant. The derived cluster
mass is quite sensitive to the N(z) for the FBG's. At one extreme, if all the
FBG's are at z_s = 3, then the mass within a Mpc aperture is \h1 , and the mass-to-light ratio is in solar units. For the derived mass is 70\%
higher and . If follows the no evolution model (in
shape) then , and if all the FBG's lie at z_s\la 1 the
required exceeds . These data provide clear evidence that large,
dense mass concentrations existed at early epochs; that they can be weighed
efficiently by weak lensing observations; and that most of the FBG's are at
high redshift.Comment: Submitted to ApJ, 15 pages (incl 8 figs, 3 of which are plates).
Plate images not included, but are available from
ftp://hubble.ifa.hawaii.edu/pub/ger/ms1054/ms1054_fig[1,3,5].ps.
A combined HST/CFH12k/XMM survey of X-ray luminous clusters of galaxies at z~0.2
We describe a project to study a sample of X-ray luminous clusters of
galaxies at redshift z~0.2 at several scales (with HST/WFPC2 and CFHT/CFH12k)
and wavebands (optical and X-ray). The main aims of the project are (i) to
determine the mass profiles of the clusters on scales ranging from ~10 kpc/h to
>1.5 Mpc/h using weak and strong lensing, thereby testing theoretical
predictions of a ``universal mass profile'', and (ii) to calibrate the M_tot -
T_X relation in view of future application in the study of the evolution of the
cluster mass function at higher redshift.Comment: 4 pages, 2 figures, Proceedings of the XXth Moriond Astrophysics
Meeting ``Cosmological Physics with Gravitational Lensing'', J.-P. Kneib, Y.
Mellier, M. Moniez and J. Tran Thanh Van eds., 200
A CFH12k lensing survey of X-ray luminous galaxy clusters. II. Weak lensing analysis and global correlations
Aims. We present a wide-field multi-color survey of a homogeneous sample of eleven clusters of galaxies for which we measure total masses and mass distributions from weak lensing. This sample, spanning a small range in both X-ray luminosity and redshift, is ideally suited to determining the normalisation of scaling relations between X-ray properties of clusters and their masses (the M â T_X and the M â L_X relations) and also estimating the scatter in these relations at a fixed luminosity.
Methods. The eleven clusters in our sample are all X-ray luminous and span a narrow redshift range at z = 0.21 ± 0.04. The weak lensing analysis of the sample is based on ground-based wide-field imaging obtained with the CFH12k camera on CFHT. We use the methodology developed and applied previously on the massive cluster Abell 1689. A Bayesian method, implemented in the Im2shape software, is used to fit the shape parameters of the faint background galaxies and to correct for PSF smearing. A multi-color selection of the background galaxies is applied to retrieve the weak lensing signal, resulting in a background density of sources of ~10 galaxies per square arc minute. With the present data, shear profiles are measured in all clusters out to at least 2 Mpc (more than 15 from the center) with high confidence. The radial shear profiles are fitted with different parametric mass profiles and the virial mass M_(200) is estimated for each cluster and then compared to other physical properties.
Results. Scaling relations between mass and optical luminosity indicate an increase of the M/L ratio with luminosity (M/L â L^(0.8)) and a LXâM_(200) relation scaling as L_X â M^(0.83±0.11)_(200) while the normalization of the M_(200) â T^(3/2)_X relation is close to the one expected from hydrodynamical simulations of cluster formation as well as previous X-ray analyses. We suggest that the dispersion in the M_(200) â T_X and M_(200) â L_X relations reflects the different merging and dynamical histories for clusters of similar X-ray luminosities and intrinsic variations in their measured masses. Improved statistics of clusters over a wider mass range are required for a better control of the intrinsic scatter in scaling relations
Outcomes in Trials for Management of Caries Lesions (OuTMaC):protocol
Background
Clinical trials on caries lesion management use an abundance of outcomes, hampering comparison or combination of different study results and their efficient translation into clinical practice. Core outcome sets are an agreed standardized collection of outcomes which should be measured and reported in all trials for a specific clinical area. We aim to develop a core outcome set for trials investigating management of caries lesions in primary or permanent teeth conducted in primary or secondary care encompassing all stages of disease.
Methods
To identify existing outcomes, trials on prevention and trials on management of caries lesions will be screened systematically in four databases. Screening, extraction and deduplication will be performed by two researchers until consensus is reached. The definition of the core outcome set will by based on an e-Delhi consensus process involving key stakeholders namely patients, dentists, clinical researchers, health economists, statisticians, policy-makers and industry representatives. For the first stage of the Delphi process, a patient panel and a separate panel consisting of researchers, clinicians, teachers, industry affiliated researchers, policy-makers, and other interested parties will be held. An inclusive approach will be taken to involve panelists from a wide variety of socio-economic and geographic backgrounds. Results from the first round will be summarized and fed back to individuals for the second round, where panels will be combined and allowed to modify their scoring in light of the full panelâs opinion. Necessity for a third round will be dependent on the outcome of the first two. Agreement will be measured via defined consensus rules; up to a maximum of seven outcomes. If resources allow, we will investigate features that influence decision making for different groups.
Discussion
By using an explicit, transparent and inclusive multi-step consensus process, the planned core outcome set should be justifiable, relevant and comprehensive. The dissemination and application of this core outcome set should improve clinical trials on managing caries lesions and allow comparison, synthesis and implementation of scientific data.
Trial registration
Registered 12 April 2015 at COMET (http://www.comet-initiative.org
Spectroscopic follow up of arclets in AC114 with the VLT
We present the first results on the VLT/FORS-1 spectroscopic survey of
amplified sources and multiple images in the lensing cluster AC114. Background
sources were selected in the cluster core, close to the critical lines, using
photometric redshifts combined with lensing inversion criteria. Spectroscopic
results are given, together with a brief summary of the properties of some of
these high-z galaxies.Comment: 4pages. To appear in the Proceedings of the XXth Moriond Astrophysics
Meeting "Cosmological Physics with Gravitational Lensing", eds. J.-P. Kneib,
Y. Mellier, M. Moniez and J. Tran Thanh Van, Les Arcs, France, March
11th-18th 200
Utilizing Skylab data in on-going resources management programs in the state of Ohio
The author has identified the following significant results. The use of Skylab imagery for total area woodland surveys was found to be more accurate and cheaper than conventional surveys using aerial photo-plot techniques. Machine-aided (primarily density slicing) analyses of Skylab 190A and 190B color and infrared color photography demonstrated the feasibility of using such data for differentiating major timber classes including pines, hardwoods, mixed, cut, and brushland providing such analyses are made at scales of 1:24,000 and larger. Manual and machine-assisted image analysis indicated that spectral and spatial capabilities of Skylab EREP photography are adequate to distinguish most parameters of current, coal surface mining concern associated with: (1) active mining, (2) orphan lands, (3) reclaimed lands, and (4) active reclamation. Excellent results were achieved when comparing Skylab and aerial photographic interpretations of detailed surface mining features. Skylab photographs when combined with other data bases (e.g., census, agricultural land productivity, and transportation networks), provide a comprehensive, meaningful, and integrated view of major elements involved in the urbanization/encroachment process
A new deep SCUBA survey of gravitationally lensing clusters
We have conducted a new deep SCUBA survey, which has targetted 12 lensing
galaxy clusters and one blank field. In this survey we have detected several
sub-mJy sources after correcting for the gravitational lensing by the
intervening clusters. We here present the preliminary results and point out two
highlights.Comment: 4 pages, 2 figures, "Multiwavelength Cosmology" Mykonos, June 2003,
conference proceeding
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