222 research outputs found
On Preferred Axes in WMAP Cosmic Microwave Background Data after Subtraction of the Integrated Sachs-Wolfe Effect
There is currently a debate over the existence of claimed statistical
anomalies in the cosmic microwave background (CMB), recently confirmed in
Planck data. Recent work has focussed on methods for measuring statistical
significance, on masks and on secondary anisotropies as potential causes of the
anomalies. We investigate simultaneously the method for accounting for masked
regions and the foreground integrated Sachs-Wolfe (ISW) signal. We search for
trends in different years of WMAP CMB data with different mask treatments. We
reconstruct the ISW field due to the 2 Micron All-Sky Survey (2MASS) and the
NRAO VLA Sky Survey (NVSS) up to l=5, and we focus on the Axis of Evil (AoE)
statistic and even/odd mirror parity, both of which search for preferred axes
in the Universe. We find that removing the ISW reduces the significance of
these anomalies in WMAP data, though this does not exclude the possibility of
exotic physics. In the spirit of reproducible research, all reconstructed maps
and codes will be made available for download at
http://www.cosmostat.org/anomaliesCMB.html.Comment: Figure 1-2 and Tables 1, D.1, D.2 updated. Main conclusions
unchanged. Accepted for publication in A&A. In the spirit of reproducible
research, all statistical and sparse inpainting codes as well as resulting
products which constitute main results of this paper will be made public
here: http://www.cosmostat.org/anomaliesCMB.htm
3D galaxy clustering with future wide-field surveys: Advantages of a spherical Fourier-Bessel analysis
Upcoming spectroscopic galaxy surveys are extremely promising to help in
addressing the major challenges of cosmology, in particular in understanding
the nature of the dark universe. The strength of these surveys comes from their
unprecedented depth and width. Optimal extraction of their three-dimensional
information is of utmost importance to best constrain the properties of the
dark universe. Although there is theoretical motivation and novel tools to
explore these surveys using the 3D spherical Fourier-Bessel (SFB) power
spectrum of galaxy number counts , most survey
optimisations and forecasts are based on the tomographic spherical harmonics
power spectrum . We performed a new investigation of the
information that can be extracted from the tomographic and 3D SFB techniques by
comparing the forecast cosmological parameter constraints obtained from a
Fisher analysis in the context of planned stage IV wide-field galaxy surveys.
The comparison was made possible by careful and coherent treatment of
non-linear scales in the two analyses. Nuisance parameters related to a scale-
and redshift-dependent galaxy bias were also included for the first time in the
computation of both the 3D SFB and tomographic power spectra. Tomographic and
3D SFB methods can recover similar constraints in the absence of systematics.
However, constraints from the 3D SFB analysis are less sensitive to unavoidable
systematics stemming from a redshift- and scale-dependent galaxy bias. Even for
surveys that are optimised with tomography in mind, a 3D SFB analysis is more
powerful. In addition, for survey optimisation, the figure of merit for the 3D
SFB method increases more rapidly with redshift, especially at higher
redshifts, suggesting that the 3D SFB method should be preferred for designing
and analysing future wide-field spectroscopic surveys.Comment: 12 pages, 6 Figures. Python package for cosmological forecasts
available at https://cosmicpy.github.io . Updated figures. Matches published
versio
Low-l CMB Analysis and Inpainting
Reconstruction of the CMB in the Galactic plane is extremely difficult due to
the dominant foreground emissions such as Dust, Free-Free or Synchrotron. For
cosmological studies, the standard approach consists in masking this area where
the reconstruction is not good enough. This leads to difficulties for the
statistical analysis of the CMB map, especially at very large scales (to study
for e.g., the low quadrupole, ISW, axis of evil, etc). We investigate in this
paper how well some inpainting techniques can recover the low- spherical
harmonic coefficients. We introduce three new inpainting techniques based on
three different kinds of priors: sparsity, energy and isotropy, and we compare
them. We show that two of them, sparsity and energy priors, can lead to
extremely high quality reconstruction, within 1% of the cosmic variance for a
mask with Fsky larger than 80%.Comment: Submitte
Planck CMB Anomalies: Astrophysical and Cosmological Secondary Effects and the Curse of Masking
Large-scale anomalies have been reported in CMB data with both WMAP and
Planck data. These could be due to foreground residuals and or systematic
effects, though their confirmation with Planck data suggests they are not due
to a problem in the WMAP or Planck pipelines. If these anomalies are in fact
primordial, then understanding their origin is fundamental to either validate
the standard model of cosmology or to explore new physics. We investigate three
other possible issues: 1) the trade-off between minimising systematics due to
foreground contamination (with a conservative mask) and minimising systematics
due to masking, 2) astrophysical secondary effects (the kinetic Doppler
quadrupole and kinetic Sunyaev-Zel'dovich effect), and 3) secondary
cosmological signals (the integrated Sachs-Wolfe effect). We address the
masking issue by considering new procedures that use both WMAP and Planck to
produce higher quality full-sky maps using the sparsity methodology (LGMCA
maps). We show the impact of masking is dominant over that of residual
foregrounds, and the LGMCA full-sky maps can be used without further processing
to study anomalies. We consider four official Planck PR1 and two LGMCA CMB
maps. Analysis of the observed CMB maps shows that only the low quadrupole and
quadrupole-octopole alignment seem significant, but that the planar octopole,
Axis of Evil, mirror parity and cold spot are not significant in nearly all
maps considered. After subtraction of astrophysical and cosmological secondary
effects, only the low quadrupole may still be considered anomalous, meaning the
significance of only one anomaly is affected by secondary effect subtraction
out of six anomalies considered. In the spirit of reproducible research all
reconstructed maps and codes will be made available for download here
http://www.cosmostat.org/anomaliesCMB.html.Comment: Summary of results given in Table 2. Accepted for publication in
JCAP, 4th August 201
Joint Planck and WMAP CMB Map Reconstruction
We present a novel estimate of the cosmological microwave background (CMB)
map by combining the two latest full-sky microwave surveys: WMAP nine-year and
Planck PR1. The joint processing benefits from a recently introduced component
separation method coined "local-generalized morphological component analysis''
(LGMCA) based on the sparse distribution of the foregrounds in the wavelet
domain. The proposed estimation procedure takes advantage of the IRIS 100
micron as an extra observation on the galactic center for enhanced dust
removal. We show that this new CMB map presents several interesting aspects: i)
it is a full sky map without using any inpainting or interpolating method, ii)
foreground contamination is very low, iii) the Galactic center is very clean,
with especially low dust contamination as measured by the cross-correlation
between the estimated CMB map and the IRIS 100 micron map, and iv) it is free
of thermal SZ contamination.Comment: Astronomy and Astrophysics, accepte
Spherical 3D Isotropic Wavelets
Future cosmological surveys will provide 3D large scale structure maps with
large sky coverage, for which a 3D Spherical Fourier-Bessel (SFB) analysis in
spherical coordinates is natural. Wavelets are particularly well-suited to the
analysis and denoising of cosmological data, but a spherical 3D isotropic
wavelet transform does not currently exist to analyse spherical 3D data. The
aim of this paper is to present a new formalism for a spherical 3D isotropic
wavelet, i.e. one based on the SFB decomposition of a 3D field and accompany
the formalism with a public code to perform wavelet transforms. We describe a
new 3D isotropic spherical wavelet decomposition based on the undecimated
wavelet transform (UWT) described in Starck et al. 2006. We also present a new
fast Discrete Spherical Fourier-Bessel Transform (DSFBT) based on both a
discrete Bessel Transform and the HEALPIX angular pixelisation scheme. We test
the 3D wavelet transform and as a toy-application, apply a denoising algorithm
in wavelet space to the Virgo large box cosmological simulations and find we
can successfully remove noise without much loss to the large scale structure.
We have described a new spherical 3D isotropic wavelet transform, ideally
suited to analyse and denoise future 3D spherical cosmological surveys, which
uses a novel Discrete Spherical Fourier-Bessel Transform. We illustrate its
potential use for denoising using a toy model. All the algorithms presented in
this paper are available for download as a public code called MRS3D at
http://jstarck.free.fr/mrs3d.htmlComment: 9 pages + appendices. Public code can be downloaded at
http://jstarck.free.fr/mrs3d.html Corrected typos and updated references.
Accepted for publication in Astronomy and Astrophysic
Weak lensing forecasts for dark energy, neutrinos and initial conditions
Weak gravitational lensing provides a sensitive probe of cosmology by measuring the mass distribution and the geometry of the low-redshift Universe. We show how an all-sky weak lensing tomographic survey can jointly constrain different sets of cosmological parameters describing dark energy, massive neutrinos (hot dark matter) and the primordial power spectrum. In order to put all sectors on an equal footing, we introduce a new parameter β, the second-order running spectral index. Using the Fisher matrix formalism with and without cosmic microwave background (CMB) priors, we examine how the constraints vary as the parameter set is enlarged. We find that weak lensing with CMB priors provides robust constraints on dark energy parameters and can simultaneously provide strong constraints on all three sectors. We find that the dark energy sector is largely insensitive to the inclusion of the other cosmological sectors. Implications for the planning of future surveys are discusse
iCosmo: an Interactive Cosmology Package
Aims: The interactive software package iCosmo, designed to perform
cosmological calculations is described. Methods: iCosmo is a software package
to perform interactive cosmological calculations for the low redshift universe.
Computing distance measures, the matter power spectrum, and the growth factor
is supported for any values of the cosmological parameters. It also computes
derived observed quantities for several cosmological probes such as cosmic
shear, baryon acoustic oscillations and type Ia supernovae. The associated
errors for these observables can be derived for customised surveys, or for
pre-set values corresponding to current or planned instruments. The code also
allows for the calculation of cosmological forecasts with Fisher matrices which
can be manipulated to combine different surveys and cosmological probes. The
code is written in the IDL language and thus benefits from the convenient
interactive features and scientific library available in this language. iCosmo
can also be used as an engine to perform cosmological calculations in batch
mode, and forms a convenient adaptive platform for the development of further
cosmological modules. With its extensive documentation, it may also serve as a
useful resource for teaching and for newcomers in the field of cosmology.
Results: The iCosmo package is described with various examples and command
sequences. The code is freely available with documentation at
http://www.icosmo.org, along with an interactive web interface and is part of
the Initiative for Cosmology, a common archive for cosmological resources.Comment: 6 pages including 2 tables and 4 figures. Accepted and published in
Astronomy and Astrophysics. Public code and further resources available at
http://www.icosmo.or
Internal and External Induced Circular Dichroism in Cyclodextrin Complexes: A Study of the Complexes of α-Cyclodextrin with (R)-3-Methylcyclopentanone and Cyclopentanone
The circular dichroism (CD) of (R)-3-methylcyclopentanone
1 in the presence of a-cyclodextrin (aCx) in -water has been
measured. The formation constant (K\u27 = 24 mol-1 litre) of al-l
complex, specific CD (do = +1.74) of 1 in water solution, and
specific CD of this complex in water (t1c\u27 = +1.4,5)have been
calculated. Similarly, the induced CD (ICD) of cyclopentanone
2 in the presence of aCx in water has been measured. The formation
constant (K = 25 mol-1 litre) of a 1-1 complex and the
specific CD (t1c\u27 = -0.034)of this complex have been calculated.
A model is presented for the interpretation of the lCD data.
Various theoretical possibi1ities are discussed. A comparison with
X-Ray and low-temperature neutron-diffraction data for the
(2-aCx) complex is attempted. It seems reasonable to conclude
that there is only a weak chiral discrimination in this complex in
water solution at room temperature
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