93 research outputs found
Lensing magnification effects on the cosmic shear statistics
Gravitational lensing causes a correlation between a population of foreground
large-scale structures and the observed number density of the background
distant galaxies as a consequence of the flux magnification and the lensing
area distortion. This correlation has not been taken into account in
calculations of the theoretical predictions of the cosmic shear statistics but
may cause a systematic error in a cosmic shear measurement. We examine its
impact on the cosmic shear statistics using the semi-analytic approach. We find
that the lensing magnification has no practical influence on the cosmic shear
variance. Exploring possible shapes of redshift distribution of source
galaxies, we find that the relative amplitude of the effect on the convergence
skewness is 3% at mostComment: 7 pages, 1 figure, accepted for publication in MNRA
Cosmological constraints from Subaru weak lensing cluster counts
We present results of weak lensing cluster counts obtained from 11 sq.deg
SuprimeCam data. Although the area is much smaller than previous work dealing
with weak lensing peak statistics, the number density of galaxies usable for
weak lensing analysis is about twice as large as those. The higher galaxy
number density reduces the noise in the weak lensing mass maps, and thus
increases the signal-to-noise ratio of peaks of the lensing signal due to
massive clusters. This enables us to construct a weak lensing selected cluster
sample by adopting a high threshold S/N, such that the contamination rate due
to false signals is small. We find 6 peaks with S/N>5. For all the peaks,
previously identified clusters of galaxies are matched within a separation of 1
arcmin, demonstrating good correspondence between the peaks and clusters of
galaxies. We evaluate the statistical error using mock weak lensing data, and
find Npeak=6+/-3.1 in an effective area of 9.0 sq.deg. We compare the measured
weak lensing cluster counts with the theoretical model prediction based on halo
models and place the constraint on Omega_m-sigma_8 plane which is found to be
consistent with currently standard LCDM models. It is demonstrated that the
weak lensing cluster counts can place a unique constraint on sigma_8-c_0 plane,
where c_0 is the normalization of the dark matter halo mass-concentration
relationship. Finally we discuss prospects for ongoing/future wide field
optical galaxy surveys.Comment: 15 pages, 11 figures, submitted to PASJ, comments welcom
Modeling peculiar velocities of dark matter halos
We present a simple model that accurately describes various statistical
properties of peculiar velocities of dark matter halos. We pay particular
attention to the following two effects; first, the evolution of the halo
peculiar velocity depends on the local matter density, instead of the global
density. Second, dark matter halos are biased tracers of the underlying mass
distribution, thus halos tend to be located preferentially at high density
regions. For the former, we develop an empirical model calibrated with N-body
simulations, while for the latter, we use a conventional halo bias models based
on the extended Press-Schechter model combined with an empirical log-normal
probability distribution function of the mass density distribution. We find
that compared with linear theory, the present model significantly improves the
accuracy of predictions of statistical properties of the halo peculiar velocity
field including the velocity dispersion, the probability distribution function,
and the pairwise velocity dispersion at large separations. Thus our model
predictions may be useful in analyzing future observations of the peculiar
velocities of galaxy clusters.Comment: This paper was published in MNRAS, 343, 1312 (2003). Owing to an
error in numerical computations, some incorrect results were presented there.
Erratum is to be published in MNRAS. Conclusions of the original version are
unaffected by the correction. This version supersedes the original versio
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