1,421 research outputs found
Modeling the reconstructed BAO in Fourier space
The density field reconstruction technique, which was developed to partially
reverse the nonlinear degradation of the Baryon Acoustic Oscillation (BAO)
feature in the galaxy redshift surveys, has been successful in substantially
improving the cosmology constraints from recent galaxy surveys such as Baryon
Oscillation Spectroscopic Survey (BOSS). We estimate the efficiency of the
reconstruction method as a function of various reconstruction details. To
directly quantify the BAO information in nonlinear density fields before and
after reconstruction, we calculate the cross-correlations (i.e., propagators)
of the pre(post)-reconstructed density field with the initial linear field
using a mock galaxy sample that is designed to mimic the clustering of the BOSS
CMASS galaxies. The results directly provide the BAO damping as a function of
wavenumber that can be implemented into the Fisher matrix analysis. We focus on
investigating the dependence of the propagator on a choice of smoothing filters
and on two major different conventions of the redshift-space density field
reconstruction that have been used in literature. By estimating the BAO
signal-to-noise for each case, we predict constraints on the angular diameter
distance and Hubble parameter using the Fisher matrix analysis. We thus
determine an optimal Gaussian smoothing filter scale for the signal-to-noise
level of the BOSS CMASS. We also present appropriate BAO fitting models for
different reconstruction methods based on the first and second order Lagrangian
perturbation theory in Fourier space. Using the mock data, we show that the
modified BAO fitting model can substantially improve the accuracy of the BAO
position in the best fits as well as the goodness of the fits.Comment: 21 pages, 7 figures, 1 table. Minor revisions. Matches version
accepted by MNRA
A complete FFT-based decomposition formalism for the redshift-space bispectrum
To fully extract cosmological information from nonlinear galaxy distribution
in redshift space, it is essential to include higher-order statistics beyond
the two-point correlation function. In this paper, we propose a new
decomposition formalism for computing the anisotropic bispectrum in redshift
space and for measuring it from galaxy samples. Our formalism uses tri-polar
spherical harmonic decomposition with zero total angular momentum to compress
the 3D modes distribution in the redshift-space bispectrum. This approach
preserves three fundamental properties of the Universe: statistical
homogeneity, isotropy, and parity-symmetry, allowing us to efficiently separate
the anisotropic signal induced by redshift-space distortions (RSDs) and the
Alcock-Paczy\'{n}ski (AP) effect from the isotropic bispectrum. The relevant
expansion coefficients in terms of the anisotropic signal are reduced to one
multipole index , and the modes are induced only by the RSD or AP
effects. Our formalism has two advantages: (1) we can make use of Fast Fourier
Transforms (FFTs) to measure the bispectrum; (2) it gives a simple expression
to correct for the survey geometry, i.e., the survey window function. As a
demonstration, we measure the decomposed bispectrum from the Baryon Oscillation
Spectroscopic Survey (BOSS) Data Release 12, and, for the first time, present a
detection of the anisotropic bispectrum in the mode.Comment: 23 pages, 13 figure
Detecting Baryon Acoustic Oscillations in Dark Matter from Kinematic Weak Lensing Surveys
We investigate the feasibility of extracting Baryon Acoustic Oscillations
(BAO) from cosmic shear tomography. We particularly focus on the BAO scale
precision that can be achieved by future spectroscopy-based, kinematic weak
lensing (KWL) surveys \citep[e.g.,][]{Huff13} in comparison to the traditional
photometry-based weak lensing surveys. We simulate cosmic shear tomography data
of such surveys with a few simple assumptions to focus on the BAO information,
extract the spacial power spectrum, and constrain the recovered BAO feature.
Due to the small shape noise and the shape of the lensing kernel, we find that
a Dark Energy Task Force Stage IV version of such KWL survey can detect the BAO
feature in dark matter by - and measure the BAO scale at the
precision level of 4\% while it will be difficult to detect the feature in
photometry-based weak lensing surveys. With a more optimistic assumption, a
KWL-Stage IV could achieve a BAO scale measurement with
- confidence. A built-in spectroscopic galaxy survey within such
KWL survey will allow cross-correlation between galaxies and cosmic shear,
which will tighten the constraint beyond the lower limit we present in this
paper and therefore possibly allow a detection of the BAO scale bias between
galaxies and dark matter.Comment: 18 pages, 10 figures; revised arguments in section 2, results
unchange
Theoretical Systematics of Future Baryon Acoustic Oscillation Surveys
Future Baryon Acoustic Oscillation surveys aim at observing galaxy clustering
over a wide range of redshift and galaxy populations at great precision,
reaching tenths of a percent, in order to detect any deviation of dark energy
from the \LCDM model. We utilize a set of paired quasi-\Nb\, FastPM
simulations that were designed to mitigate the sample variance effect on the
BAO feature and evaluated the BAO systematics as precisely as . We
report anisotropic BAO scale shifts before and after density field
reconstruction in the presence of redshift-space distortions over a wide range
of redshift, galaxy/halo biases, and shot noise levels. We test different
reconstruction schemes and different smoothing filter scales, and introduce
physically-motivated BAO fitting models. For the first time, we derive a
Galilean-invariant infrared resummed model for halos in real and redshift
space. We test these models from the perspective of robust BAO measurements and
non-BAO information such as growth rate and nonlinear bias. We find that
pre-reconstruction BAO scale has moderate fitting-model dependence at the level
of for matter while the dependence is substantially reduced to
less than for halos. We find that post-reconstruction BAO shifts are
generally reduced to below in the presence of galaxy/halo bias and show
much smaller fitting model dependence. Different reconstruction conventions can
potentially make a much larger difference on the line-of-sight BAO scale, upto
. Meanwhile, the precision (error) of the BAO measurements is quite
consistent regardless of the choice of the fitting model or reconstruction
convention.Comment: 33 pages, 19 figures, 4 tables. Submitted to MNRAS. Matches version
accepted to MNRAS. Moderate changes were made during revision including a
comparison between TreePM and FastPM BAO featur
Improved forecasts for the baryon acoustic oscillations and cosmological distance scale
We present the cosmological distance errors achievable using the baryon
acoustic oscillations as a standard ruler. We begin from a Fisher matrix
formalism that is upgraded from Seo & Eisenstein (2003). We isolate the
information from the baryonic peaks by excluding distance information from
other less robust sources. Meanwhile we accommodate the Lagrangian displacement
distribution into the Fisher matrix calculation to reflect the gradual loss of
information in scale and in time due to nonlinear growth, nonlinear bias, and
nonlinear redshift distortions. We then show that we can contract the
multi-dimensional Fisher matrix calculations into a 2-dimensional or even
1-dimensional formalism with physically motivated approximations. We present
the resulting fitting formula for the cosmological distance errors from galaxy
redshift surveys as a function of survey parameters and nonlinearity, which
saves us going through the 12-dimensional Fisher matrix calculations. Finally,
we show excellent agreement between the distance error estimates from the
revised Fisher matrix and the precision on the distance scale recovered from
N-body simulations.Comment: Submitted to ApJ, 21 pages, LaTe
A 2.5% measurement of the growth rate from small-scale redshift space clustering of SDSS-III CMASS galaxies
We perform the first fit to the anisotropic clustering of SDSS-III CMASS DR10
galaxies on scales of ~ 0.8 - 32 Mpc/h. A standard halo occupation distribution
model evaluated near the best fit Planck LCDM cosmology provides a good fit to
the observed anisotropic clustering, and implies a normalization for the
peculiar velocity field of M ~ 2 x 10^13 Msun/h halos of f*sigma8(z=0.57) =
0.450 +/- 0.011. Since this constraint includes both quasi-linear and
non-linear scales, it should severely constrain modified gravity models that
enhance pairwise infall velocities on these scales. Though model dependent, our
measurement represents a factor of 2.5 improvement in precision over the
analysis of DR11 on large scales, f*sigma8(z=0.57) = 0.447 +/- 0.028, and is
the tightest single constraint on the growth rate of cosmic structure to date.
Our measurement is consistent with the Planck LCDM prediction of 0.480 +/-
0.010 at the ~1.9 sigma level. Assuming a halo mass function evaluated at the
best fit Planck cosmology, we also find that 10% of CMASS galaxies are
satellites in halos of mass M ~ 6 x 10^13 Msun/h. While none of our tests and
model generalizations indicate systematic errors due to an insufficiently
detailed model of the galaxy-halo connection, the precision of these first
results warrant further investigation into the modeling uncertainties and
degeneracies with cosmological parameters.Comment: 24 pages, 20 figures, submitted to MNRAS. v2 is 27 pages, 23 figures,
accepted by MNRA
A ground-based 21cm Baryon acoustic oscillation survey
Baryon acoustic oscillations (BAO) provide a robust standard ruler with which
to measure the acceleration of the Universe. The BAO feature has so far been
detected in optical galaxy surveys. Intensity mapping of neutral hydrogen
emission with a ground-based radio telescope provides another promising window
for measuring BAO at redshifts of order unity for relatively low cost. While
the cylindrical radio telescope (CRT) proposed for these measurements will have
excellent redshift resolution, it will suffer from poor angular resolution (a
few arcminutes at best). We investigate the effect of angular resolution on the
standard ruler test with BAO, using the Dark Energy Task Force Figure of Merit
as a benchmark. We then extend the analysis to include variations in the
parameters characterizing the telescope and the underlying physics. Finally, we
optimize the survey parameters (holding total cost fixed) and present an
example of a CRT BAO survey that is competitive with Stage III dark energy
experiments. The tools developed here form the backbone of a publicly available
code that can be used to obtain estimates of cost and Figure of Merit for any
set of parameters.Comment: ApJ accepted version. Important changes in section 2 and 3 - uses a
more realistic instrument response model and removed the discussion of
aliasing effect. The conclusions remain the same. Typos fixed (including eq
5). 11 emulated apj pages with 7 figures and 1 tabl
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