22 research outputs found
Observational constraints of an anisotropic boost due to the projection effects using redMaPPer clusters
Optical clusters identified from red-sequence galaxies suffer from projection
effects, where interloper galaxies along the line-of-sight to a cluster are
mistaken as genuine members of the cluster. In the previous study (Sunayama et
al. 2020), we found that the projection effects cause the boost on the
amplitudes of clustering and lensing on large scale compared to the expected
amplitudes in the absence of any projection effects. These boosts are caused by
preferential selections of filamentary structure aligned to the line-of-sight
due to distance uncertainties in photometric surveys. We model the projection
effects with two simple assumptions and develop a novel method to quantify the
size of the boost using cluster-galaxy cross-correlation functions. We validate
our method using mock cluster catalogs built from cosmological N-body
simulations and find that we can obtain unbiased constraints on the boost
parameter with our model. We then apply our analysis on the SDSS redMaPPer
clusters and find that the size of the boost is roughly 20% for all the
richness bins except the cluster sample with the richness bin . This is the first study to constrain the boost parameter independent
from cluster cosmology studies and provides a self-consistency test for the
projection effects.Comment: 13 pages, 11 figure
Bispectrum as Baryon Acoustic Oscillation Interferometer
The galaxy bispectrum, measuring excess clustering of galaxy triplets, offers
a probe of dark energy via baryon acoustic oscillations (BAOs). However up to
now it has been severely underused due to the combinatorically explosive number
of triangles. Here we exploit interference in the bispectrum to identify
triangles that amplify BAOs. This approach reduces the computational cost of
estimating covariance matrices, offers an improvement in BAO constraints
equivalent to lengthening BOSS by 30%, and simplifies adding bispectrum BAO
information to future large-scale redshift survey analyses.Comment: 6 pages, 3 figures; revised to match published versio
Robustness of Baryon Acoustic Oscillations Measurements with Photometric Redshift Uncertainties
We investigate the robustness of baryon acoustic oscillations (BAO)
measurements with a photometric galaxy sample using mock galaxy catalogs with
various sizes of photometric redshift (photo-) uncertainties. We first
investigate the robustness of BAO measurements, assuming we have a perfect
knowledge of photo- uncertainties. We find that the BAO shift parameter
can be constrained in an unbiased manner for various sizes of
photometric redshift uncertainties at , , and as long as
the number density of galaxies is high. A sparse galaxy sample causes
additional noise in the covariance matrix calculation and it can bias the
constraint on . Next, we investigate the scenario where incorrect
photometric redshift uncertainties are assumed in the fitting model and find
that underestimating the photo- uncertainty leads to a degradation in the
constraining power on . In addition, we investigate BAO measurements
with a cross-correlation signal between a spec- sample and a photo-
sample. We find BAO constraints are unbiased and slightly tighter than the
auto-correlation signal of a photo- sample. We also quantify the
constraining power on assuming the LSST-like covariance and
find that the 95\% confidence level is -
corresponding to the photo- uncertainties of 1\% to 3\% respectively.
Finally, we examine whether the skewness in the photometric redshift can bias
the constraint on and confirm that the constraint on is
unbiased even if we use a fitting model assuming a Gaussian photo-
uncertainty.Comment: 10 pages, 11 figures, 3 table
Galaxy-galaxy weak-lensing measurement from SDSS: II. host halo properties of galaxy groups
As the second paper of a series on studying galaxy-galaxy lensing signals
using the Sloan Digital Sky Survey Data Release 7 (SDSS DR7), we present our
measurement and modelling of the lensing signals around groups of galaxies. We
divide the groups into four halo mass bins, and measure the signals around four
different halo-center tracers: brightest central galaxy (BCG),
luminosity-weighted center, number-weighted center and X-ray peak position. For
X-ray and SDSS DR7 cross identified groups, we further split the groups into
low and high X-ray emission subsamples, both of which are assigned with two
halo-center tracers, BCGs and X-ray peak positions. The galaxy-galaxy lensing
signals show that BCGs, among the four candidates, are the best halo-center
tracers. We model the lensing signals using a combination of four
contributions: off-centered NFW host halo profile, sub-halo contribution,
stellar contribution, and projected 2-halo term. We sample the posterior of 5
parameters i.e., halo mass, concentration, off-centering distance, sub halo
mass, and fraction of subhalos via a MCMC package using the galaxy-galaxy
lensing signals. After taking into account the sampling effects (e.g. Eddington
bias), we found the best fit halo masses obtained from lensing signals are
quite consistent with those obtained in the group catalog based on an abundance
matching method, except in the lowest mass bin. Subject headings: (cosmology:)
gravitational lensing, galaxies: clusters: generalComment: 12 pages, 7 figures, submitted to Ap
Dark Energy Survey Year 1 Clusters are Consistent with Planck
The recent Dark Energy Survey Year 1 (DES-Y1) analysis of galaxy cluster
abundances and weak lensing produced and
constraints in 5.6 tension with Planck. It is suggested in that work
that this tension is driven by unmodelled systematics in optical cluster
selection. We present a novel simulation-based forward modeling framework that
explicitly incorporates cluster selection into its model predictions. Applying
this framework to the DES-Y1 data we find consistency with Planck, resolving
the tension found in the DES-Y1 analysis. An extension of this approach to the
final DES data set will produce robust constraints on CDM parameters
and correspondingly strong tests of cosmological models.Comment: 6 pages, 2 figures, 1 table, Supplemental material with 2 figures.
Submitted to Physical Review Letter
Mitigating the impact of fiber assignment on clustering measurements from deep galaxy redshift surveys
We examine the impact of fiber assignment on clustering measurements from
fiber-fed spectroscopic galaxy surveys. We identify new effects which were
absent in previous, relatively shallow galaxy surveys such as Baryon
Oscillation Spectroscopic Survey . Specifically, we consider deep surveys
covering a wide redshift range from z=0.6 to z=2.4, as in the Subaru Prime
Focus Spectrograph survey. Such surveys will have more target galaxies than we
can place fibers on. This leads to two effects. First, it eliminates
fluctuations with wavelengths longer than the size of the field of view, as the
number of observed galaxies per field is nearly fixed to the number of
available fibers. We find that we can recover the long-wavelength fluctuation
by weighting galaxies in each field by the number of target galaxies. Second,
it makes the preferential selection of galaxies in under-dense regions. We
mitigate this effect by weighting galaxies using the so-called individual
inverse probability. Correcting these two effects, we recover the underlying
correlation function at better than 1 percent accuracy on scales greater than
10 Mpc/h.Comment: 17 pages, 11 figure
Emergent gravity fails to explain color-dependent galaxy-galaxy lensing signals from SDSS Dr7
We test the Emergent Gravity(EG) theory using the galaxy-galaxy lensing
technique based on SDSS DR7 data. In the EG scenario, we do not expect color
dependence of the galaxy sample in the 'apparent dark matter' predicted by EG,
which is exerted only by the baryonic mass. If the baryonic mass is similar,
then the predicted lensing profiles from the baryonic mass should be similar
according to the EG, regardless of the color of the galaxy sample. We use the
stellar mass of the galaxy as a proxy of its baryonic mass. We divide our
galaxy sample into 5 stellar mass bins, and further classify them as red and
blue subsamples in each stellar mass bin. If we set halo mass and concentration
as free parameters, CDM is favored by our data in terms of the reduced
while EG fails to explain the color dependence of ESDs from the
galaxy-galaxy lensing measurement.Comment: 7 pages, 3 figures. Accepted by Ap