137,680 research outputs found
Resistant estimates for high dimensional and functional data based on random projections
We herein propose a new robust estimation method based on random projections
that is adaptive and, automatically produces a robust estimate, while enabling
easy computations for high or infinite dimensional data. Under some restricted
contamination models, the procedure is robust and attains full efficiency. We
tested the method using both simulated and real data.Comment: 24 pages, 6 figure
Mass accretion rates of clusters of galaxies: CIRS and HeCS
We use a new spherical accretion recipe tested on N-body simulations to
measure the observed mass accretion rate (MAR) of 129 clusters in the Cluster
Infall Regions in the Sloan Digital Sky Survey (CIRS) and in the Hectospec
Cluster Survey (HeCS). The observed clusters cover the redshift range of
and the mass range of . Based on three-dimensional mass profiles of simulated
clusters reaching beyond the virial radius, our recipe returns MARs that agree
with MARs based on merger trees. We adopt this recipe to estimate the MAR of
real clusters based on measurements of the mass profile out to .
We use the caustic method to measure the mass profiles to these large radii. We
demonstrate the validity of our estimates by applying the same approach to a
set of mock redshift surveys of a sample of 2000 simulated clusters with a
median mass of as well as a sample
of 50 simulated clusters with a median mass of : the median MARs based on the caustic mass profiles of
the simulated clusters are unbiased and agree within with the median
MARs based on the real mass profile of the clusters. The MAR of the CIRS and
HeCS clusters increases with the mass and the redshift of the accreting
cluster, which is in excellent agreement with the growth of clusters in the
CDM model.Comment: 25 pages, 19 figures, 7 table
Resistant estimates for high dimensional and functional data based on random projections
We herein propose a new robust estimation method based on random projections that is adaptive and automatically produces a robust estimate, while enabling easy computations for high or infinite dimensional data. Under some restricted contamination models, the procedure is robust and attains full efficiency. We tested the method using both simulated and real data.Fil: Fraiman, Jacob Ricardo. Universidad de San Andrés; Argentina. Universidad de la República; Uruguay. Consejo Nacional de Investigaciones CientÃficas y Técnicas; ArgentinaFil: Svarc, Marcela. Consejo Nacional de Investigaciones CientÃficas y Técnicas; Argentina. Universidad de San Andrés; Argentin
Mass estimation in the outer regions of galaxy clusters
We present a technique for estimating the mass in the outskirts of galaxy
clusters where the usual assumption of dynamical equilibrium is not valid. The
method assumes that clusters form through hierarchical clustering and requires
only galaxy redshifts and positions on the sky. We apply the method to
dissipationless cosmological N-body simulations where galaxies form and evolve
according to semi-analytic modelling. The method recovers the actual cluster
mass profile within a factor of two to several megaparsecs from the cluster
centre. This error originates from projection effects, sparse sampling, and
contamination by foreground and background galaxies. In the absence of velocity
biases, this method can provide an estimate of the mass-to-light ratio on
scales ~1-10 Mpc/h where this quantity is still poorly known.Comment: 14 pages, 7 figures, MN LaTeX style, MNRAS, in pres
Spatial Sign Correlation
A new robust correlation estimator based on the spatial sign covariance
matrix (SSCM) is proposed. We derive its asymptotic distribution and influence
function at elliptical distributions. Finite sample and robustness properties
are studied and compared to other robust correlation estimators by means of
numerical simulations.Comment: 20 pages, 7 figures, 2 table
Quasiconvex Programming
We define quasiconvex programming, a form of generalized linear programming
in which one seeks the point minimizing the pointwise maximum of a collection
of quasiconvex functions. We survey algorithms for solving quasiconvex programs
either numerically or via generalizations of the dual simplex method from
linear programming, and describe varied applications of this geometric
optimization technique in meshing, scientific computation, information
visualization, automated algorithm analysis, and robust statistics.Comment: 33 pages, 14 figure
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