1,284 research outputs found
COMMENCEMENT ’90: A Historic Occasion: Beating the Odds
Commencement Speech by Marian Wright Edelme
Investing in our Children
As adults we are responsible for meeting the needs of children. It is our moral obligation to help children survive, thrive and grow into self-sufficient adults - caring parents, competent workers with a fair opportunity for success and fulfillment, and responsible citizens. Adult society must provide children with food, shelter, medical care, and an environment that is both secure and stimulating. Children need our assistance to obtain the decent education they deserve, to prepare to compete in the job market, to make sound decisions about when to become parents, to feel valued and valuable, and to feel that they have a fair chance to succeed
Weak Lensing Peak Finding: Estimators, Filters, and Biases
Large catalogs of shear-selected peaks have recently become a reality. In
order to properly interpret the abundance and properties of these peaks, it is
necessary to take into account the effects of the clustering of source
galaxies, among themselves and with the lens. In addition, the preferred
selection of lensed galaxies in a flux- and size-limited sample leads to
fluctuations in the apparent source density which correlate with the lensing
field (lensing bias). In this paper, we investigate these issues for two
different choices of shear estimators which are commonly in use today:
globally-normalized and locally-normalized estimators. While in principle
equivalent, in practice these estimators respond differently to systematic
effects such as lensing bias and cluster member dilution. Furthermore, we find
that which estimator is statistically superior depends on the specific shape of
the filter employed for peak finding; suboptimal choices of the
estimator+filter combination can result in a suppression of the number of high
peaks by orders of magnitude. Lensing bias generally acts to increase the
signal-to-noise \nu of shear peaks; for high peaks the boost can be as large as
\Delta \nu ~ 1-2. Due to the steepness of the peak abundance function, these
boosts can result in a significant increase in the abundance of shear peaks. A
companion paper (Rozo et al., 2010) investigates these same issues within the
context of stacked weak lensing mass estimates.Comment: 11 pages, 8 figures; comments welcom
Optimal capture of non-Gaussianity in weak lensing surveys: power spectrum, bispectrum and halo counts
We compare the efficiency of weak lensing-selected galaxy clusters counts and
of the weak lensing bispectrum at capturing non-Gaussian features in the dark
matter distribution. We use the halo model to compute the weak lensing power
spectrum, the bispectrum and the expected number of detected clusters, and
derive constraints on cosmological parameters for a large, low systematic weak
lensing survey, by focusing on the - plane and on the dark
energy equation of state. We separate the power spectrum into the resolved and
the unresolved parts of the data, the resolved part being defined as detected
clusters, and the unresolved part as the rest of the field. We consider four
kinds of clusters counts, taking into account different amount of information :
signal-to-noise ratio peak counts; counts as a function of clusters' mass;
counts as a function of clusters' redshift; and counts as a function of
clusters' mass and redshift. We show that when combined with the power
spectrum, those four kinds of counts provide similar constraints, thus allowing
one to perform the most direct counts, signal-to-noise peaks counts, and get
percent level constraints on cosmological parameters. We show that the weak
lensing bispectrum gives constraints comparable to those given by the power
spectrum and captures non-Gaussian features as well as clusters counts, its
combination with the power spectrum giving errors on cosmological parameters
that are similar to, if not marginally smaller than, those obtained when
combining the power spectrum with cluster counts. We finally note that in order
to reach its potential, the weak lensing bispectrum must be computed using all
triangle configurations, as equilateral triangles alone do not provide useful
information.Comment: Matches ApJ-accepted versio
Development of an early warning system for owners using a validated health-related quality of life (HRQL) instrument for companion animals and its use in a large cohort of dogs
No abstract available
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