841 research outputs found
Optimizing Allocation of U.S. Humanitarian Civic Assistance Projects in Support of Developing Foreign Democracy
Humanitarian projects in foreign countries are funded by the U.S. government to foster peace, prosperity, and the spread of democratic ideals around the globe. The type and scope of projects are restricted by current doctrine and funding regulations. Specifically in 2014, USAF personnel supported medical and educational construction projects/programs in the country of Belize. Within Belize, medical and educational projects were funded under the Humanitarian and Civic Assistance (HCA) program through the NEW HORIZONS exercise. Fiscal constraints, including shrinking budgets due to sequestration, have placed greater emphasis in the responsible distribution of resources and foreign assistance. The purpose of this thesis is to analyze public opinion survey data collected by the Latin American Public Opinion Project (LAPOP) and analyze predictors in satisfaction in democracy organized at the village and district level. The research findings represent suggestions, based on the population, that predict optimal placement of HCA programs
Photometric Redshifts and Photometry Errors
We examine the impact of non-Gaussian photometry errors on photometric
redshift performance. We find that they greatly increase the scatter, but this
can be mitigated to some extent by incorporating the correct noise model into
the photometric redshift estimation process. However, the remaining scatter is
still equivalent to that of a much shallower survey with Gaussian photometry
errors. We also estimate the impact of non-Gaussian errors on the spectroscopic
sample size required to verify the photometric redshift rms scatter to a given
precision. Even with Gaussian {\it photometry} errors, photometric redshift
errors are sufficiently non-Gaussian to require an order of magnitude larger
sample than simple Gaussian statistics would indicate. The requirements
increase from this baseline if non-Gaussian photometry errors are included.
Again the impact can be mitigated by incorporating the correct noise model, but
only to the equivalent of a survey with much larger Gaussian photometry errors.
However, these requirements may well be overestimates because they are based on
a need to know the rms, which is particularly sensitive to tails. Other
parametrizations of the distribution may require smaller samples.Comment: submitted to ApJ
Open cell fire-resistant foam
Candidate polyphosphazene polymers were investigated to develop a fire-resistant, thermally stable and flexible open cell foam. The copolymers were prepared in several mole ratios of the substituent side chains and a (nominal) 40:60 derivative was selected for formulation studies. Synthesis of the polymers involved solution by polymerization of hexachlorophosphazene to soluble high molecular weight poly(dichlorophosphazene), followed by derivatization of the resultant polymer in a normal fashion to give polymers in high yield and high molecular weight. Small amounts of a cure site were incorporated into the polymer for vulcanization purposes. The poly(aryloxyphosphazenes) exhibited good thermal stability and the first polymer mentioned above exhibited the best thermal behavior of all the candidate polymers studied
Discovery of a Galaxy Cluster via Weak Lensing
We report the discovery of a cluster of galaxies via its weak gravitational
lensing effect on background galaxies, the first spectroscopically confirmed
cluster to be discovered through its gravitational effects rather than by its
electromagnetic radiation. This fundamentally different selection mechanism
promises to yield mass-selected, rather than baryon or photon-selected, samples
of these important cosmological probes. We have confirmed this cluster with
spectroscopic redshifts of fifteen members at z=0.276, with a velocity
dispersion of 615 km/s. We use the tangential shear as a function of source
photometric redshift to estimate the lens redshift independently and find z_l =
0.30 +- 0.08. The good agreement with the spectroscopy indicates that the
redshift evolution of the mass function may be measurable from the imaging data
alone in shear-selected surveys.Comment: revised version with minor changes, to appear in ApJ
Wide-field weak lensing by RXJ1347-1145
We present an analysis of weak lensing observations for RXJ1347-1145 over a
43' X 43' field taken in B and R filters on the Blanco 4m telescope at CTIO.
RXJ1347-1145 is a massive cluster at redshift z=0.45. Using a population of
galaxies with 20<R<26, we detect a weak lensing signal at the p<0.0005 level,
finding best-fit parameters of \sigma_v=1400^{+130}_{-140} km s^{-1} for a
singular isothermal sphere model and r_{200} = 3.5^{+0.8}_{-0.2} Mpc with c =
15^{+64}_{-10} for a NFW model in an \Omega_m = 0.3, \Omega_\Lambda = 0.7
cosmology. In addition, a mass to light ratio M/L_R =90 \pm 20 M_\odot /
L_{R\odot} was determined. These values are consistent with the previous weak
lensing study of RXJ1347--1145 by Fischer and Tyson, 1997, giving strong
evidence that systemic bias was not introduced by the relatively small field of
view in that study. Our best-fit parameter values are also consistent with
recent X-ray studies by Allen et al, 2002 and Ettori et al, 2001, but are not
consistent with recent optical velocity dispersion measurements by Cohen and
Kneib, 2002.Comment: accepted to ApJ, tentative publication 10 May 2005, v624
Mapping the 3-D Dark Matter potential with weak shear
We investigate the practical implementation of Taylor's (2002) 3-dimensional
gravitational potential reconstruction method using weak gravitational lensing,
together with the requisite reconstruction of the lensing potential. This
methodology calculates the 3-D gravitational potential given a knowledge of
shear estimates and redshifts for a set of galaxies. We analytically estimate
the noise expected in the reconstructed gravitational field, taking into
account the uncertainties associated with a finite survey, photometric redshift
uncertainty, redshift-space distortions, and multiple scattering events. In
order to implement this approach for future data analysis, we simulate the
lensing distortion fields due to various mass distributions. We create
catalogues of galaxies sampling this distortion in three dimensions, with
realistic spatial distribution and intrinsic ellipticity for both ground-based
and space-based surveys. Using the resulting catalogues of galaxy position and
shear, we demonstrate that it is possible to reconstruct the lensing and
gravitational potentials with our method. For example, we demonstrate that a
typical ground-based shear survey with redshift limit z=1 and photometric
redshifts with error Delta z=0.05 is directly able to measure the 3-D
gravitational potential for mass concentrations >10^14 M_\odot between
0.1<z<0.5, and can statistically measure the potential at much lower mass
limits. The intrinsic ellipticity of objects is found to be a serious source of
noise for the gravitational potential, which can be overcome by Wiener
filtering or examining the potential statistically over many fields. We examine
the use of the 3-D lensing potential to measure mass and position of clusters
in 3-D, and to detect clusters behind clusters.Comment: 21 pages, including 24 figures, submitted to MNRA
Probing the Relation Between X-ray-Derived and Weak-Lensing-Derived Masses for Shear-Selected Galaxy Clusters: I. A781
We compare X-ray and weak-lensing masses for four galaxy clusters that
comprise the top-ranked shear-selected cluster system in the Deep Lens Survey.
The weak-lensing observations of this system, which is associated with A781,
are from the Kitt Peak Mayall 4-m telescope, and the X-ray observations are
from both Chandra and XMM-Newton. For a faithful comparison of masses, we adopt
the same matter density profile for each method, which we choose to be an NFW
profile. Since neither the X-ray nor weak-lensing data are deep enough to well
constrain both the NFW scale radius and central density, we estimate the scale
radius using a fitting function for the concentration derived from cosmological
hydrodynamic simulations and an X-ray estimate of the mass assuming
isothermality. We keep this scale radius in common for both X-ray and
weak-lensing profiles, and fit for the central density, which scales linearly
with mass. We find that for three of these clusters, there is agreement between
X-ray and weak-lensing NFW central densities, and thus masses. For the other
cluster, the X-ray central density is higher than that from weak-lensing by 2
sigma. X-ray images suggest that this cluster may be undergoing a merger with a
smaller cluster. This work serves as an additional step towards understanding
the possible biases in X-ray and weak-lensing cluster mass estimation methods.
Such understanding is vital to efforts to constrain cosmology using X-ray or
weak-lensing cluster surveys to trace the growth of structure over cosmic time.Comment: 14 pages, 7 figures, matches version in Ap
Shear-Selected Clusters From the Deep Lens Survey III: Masses from Weak Lensing
We present weak lensing mass estimates of seven shear-selected galaxy cluster
candidates from the Deep Lens Survey. The clusters were previously identified
as mass peaks in convergence maps of 8.6 sq. deg of R band imaging, and
followed up with X-ray and spectroscopic confirmation, spanning a redshift
range 0.19 - 0.68. Most clusters contained multiple X-ray peaks, yielding 17
total mass concentrations. In this paper, we constrain the masses of these
X-ray sources with weak lensing, using photometric redshifts from the full set
of BVRz' imaging to properly weight background galaxies according to their
lensing distance ratios. We fit both NFW and singular isothermal sphere
profiles, and find that the results are insensitive to the assumed profile. We
also show that the results do not depend significantly on the assumed prior on
the position of the mass peak, but that this may become an issue in future
larger samples. The inferred velocity dispersions for the extended X-ray
sources range from 250-800 km/s, with the exception of one source for which no
lensing signal was found. This work further establishes shear selection as a
viable technique for finding clusters, but also highlights some unresolved
issues such as determination of the mass profile center without biasing the
mass estimate, and fully accounting for line-of-sight projections. A follow-up
paper will examine the mass-X-ray scaling relations of these clusters.Comment: Accepted for publication in ApJ, 27 pages, 4 figures. Some discussion
and clarification added. Cluster centre offset added to Table
Weak Lensing Detection of Cl 1604+4304 at z = 0.90
We present a weak lensing analysis of the high-redshift cluster Cl 1604+4304.
At z=0.90, this is the highest-redshift cluster yet detected with weak lensing.
It is also one of a sample of high-redshift, optically-selected clusters whose
X-ray temperatures are lower than expected based on their velocity dispersions.
Both the gas temperature and galaxy velocity dispersion are proxies for its
mass, which can be determined more directly by a lensing analysis. Modeling the
cluster as a singular isothermal sphere, we find that the mass contained within
projected radius R is 3.69+-1.47 * (R/500 kpc) 10^14 M_odot. This corresponds
to an inferred velocity dispersion of 1004+-199 km/s, which agrees well with
the measured velocity dispersion of 989+98-76 km/s (Gal & Lubin 2004). These
numbers are higher than the 575+110-85 km/s inferred from Cl 1604+4304 X-ray
temperature, however all three velocity dispersion estimates are consistent
within ~ 1.9 sigma.Comment: Revised version accepted for publication in AJ (January 2005). 2
added figures (6 figures total
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