18 research outputs found
High Performance P3M N-body code: CUBEP3M
This paper presents CUBEP3M, a publicly-available high performance
cosmological N-body code and describes many utilities and extensions that have
been added to the standard package. These include a memory-light runtime SO
halo finder, a non-Gaussian initial conditions generator, and a system of
unique particle identification. CUBEP3M is fast, its accuracy is tuneable to
optimize speed or memory, and has been run on more than 27,000 cores, achieving
within a factor of two of ideal weak scaling even at this problem size. The
code can be run in an extra-lean mode where the peak memory imprint for large
runs is as low as 37 bytes per particles, which is almost two times leaner than
other widely used N-body codes. However, load imbalances can increase this
requirement by a factor of two, such that fast configurations with all the
utilities enabled and load imbalances factored in require between 70 and 120
bytes per particles. CUBEP3M is well designed to study large scales
cosmological systems, where imbalances are not too large and adaptive
time-stepping not essential. It has already been used for a broad number of
science applications that require either large samples of non-linear
realizations or very large dark matter N-body simulations, including
cosmological reionization, halo formation, baryonic acoustic oscillations, weak
lensing or non-Gaussian statistics. We discuss the structure, the accuracy,
known systematic effects and the scaling performance of the code and its
utilities, when applicable.Comment: 20 pages, 17 figures, added halo profiles, updated to match MNRAS
accepted versio
Enhancing the cosmic shear power spectrum
Applying a transformation to a non-Gaussian field can enhance the information content of the resulting power spectrum, by reducing the correlations between Fourier modes. In the context of weak gravitational lensing, it has been shown that this gain in information content is significantly compromised by the presence of shape noise. We apply clipping to mock convergence fields, a technique which is known to be robust in the presence of noise and has been successfully applied to galaxy number density fields. When analysed in isolation the resulting convergence power spectrum returns degraded constraints on cosmological parameters. However, substantial gains can be achieved by performing a combined analysis of the power spectra derived from both the original and transformed fields. Even in the presence of realistic levels of shape noise, we demonstrate that this approach is capable of reducing the area of likelihood contours within the Omega(m) - sigma(8) plane by more than a factor of 3
Revisiting CFHTLenS cosmic shear: optimal E/B mode decomposition using COSEBIs and compressed COSEBIs
We present a re-analysis of the CFHTLenS weak gravitational lensing survey using Complete Orthogonal Sets of E/B-mode Integrals, known as COSEBIs. COSEBIs provide a complete set of functions to efficiently separate E-modes from B-modes and hence allow for robust and stringent tests for systematic errors in the data. This analysis reveals significant B-modes on large angular scales that were not previously seen using the standard E/B decomposition analyses. We find that the significance of the B-modes is enhanced when the data are split by galaxy type and analysed in tomographic redshift bins. Adding tomographic bins to the analysis increases the number of COSEBIs modes, which results in a less-accurate estimation of the covariance matrix from a set of simulations. We therefore also present the first compressed COSEBIs analysis of survey data, where the COSEBIs modes are optimally combined based on their sensitivity to cosmological parameters. In this tomographic CCOSEBIs analysis, we find the B-modes to be consistent with zero when the full range of angular scales are considered
KiDS-1000 cosmology: Combined second- and third-order shear statistics
This paper performs the first cosmological parameter analysis of the
KiDS-1000 data with second- and third-order shear statistics. This work builds
on a series of papers that describe the roadmap to third-order shear
statistics. We derive and test a combined model of the second-order shear
statistic, namely the COSEBIs and the third-order aperture mass statistics
in a tomographic set-up. We validate our
pipeline with -body simulations that mock the fourth Kilo Degree survey data
release. To model the second- and third-order statistics, we use the latest
version of \textsc{HMcode2020} for the power spectrum and \textsc{BiHalofit}
for the bispectrum. Furthermore, we use an analytic description to model
intrinsic alignments and hydro-dynamical simulations to model the effect of
baryonic feedback processes. Lastly, we decreased the dimension of the data
vector significantly by considering for the
part of the data vector only equal smoothing radii, making a data analysis of
the fourth Kilo Degree survey data release using a combined analysis of COSEBIs
third-order shear statistic possible. We first validate the accuracy of our
modelling by analysing a noise-free mock data vector assuming the KiDS-1000
error budget, finding a shift in the maximum-a-posterior of the matter density
parameter and of the structure
growth parameter . Lastly, we performed the
first KiDS-1000 cosmological analysis using a combined analysis of second- and
third-order shear statistics, where we constrained
and
. The geometric average on the
errors of and of the combined statistics increased
compared to the second-order statistic by 2.2.Comment: 19 pages, 15 figures. Updated version with arXiv ID of our companion
paper Porth et at. 202
Consistent cosmic shear in the face of systematics: a B-mode analysis of KiDS-450, DES-SV and CFHTLenS
We analyse three public cosmic shear surveys; the Kilo-Degree Survey (KiDS-450), the Dark Energy Survey (DES-SV) and the Canada France Hawaii Telescope Lensing Survey (CFHTLenS). Adopting the âCOSEBIsâ statistic to cleanly and completely separate the lensing E-modes from the non-lensing B-modes, we detect B-modes in KiDS-450 and CFHTLenS at the level of âŒ2.7Ï. For DES-SV we detect B-modes at the level of 2.8Ï in a non-tomographic analysis, increasing to a 5.5ÏB-mode detection in a tomographic analysis. In order to understand the origin of these detected B-modes we measure the B-mode signature of a range of different simulated systematics including PSF leakage, random but correlated PSF modelling errors, camera-based additive shear bias and photometric redshift selection bias. We show that any correlation between photometric-noise and the relative orientation of the galaxy to the point-spread-function leads to an ellipticity selection bias in tomographic analyses. This work therefore introduces a new systematic for future lensing surveys to consider. We find that the B-modes in DES-SV appear similar to a superposition of the B-mode signatures from all of the systematics simulated. The KiDS-450 and CFHTLenS B-mode measurements show features that are consistent with a repeating additive shear bias
RCSLenS: testing gravitational physics through the cross-correlation of weak lensing and large-scale structure
The unknown nature of dark energy motivates continued cosmological tests of
large-scale gravitational physics. We present a new consistency check based on
the relative amplitude of non-relativistic galaxy peculiar motions, measured
via redshift-space distortion, and the relativistic deflection of light by
those same galaxies traced by galaxy-galaxy lensing. We take advantage of the
latest generation of deep, overlapping imaging and spectroscopic datasets,
combining the Red Cluster Sequence Lensing Survey (RCSLenS), the
Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS), the WiggleZ Dark
Energy Survey and the Baryon Oscillation Spectroscopic Survey (BOSS). We
quantify the results using the "gravitational slip" statistic E_G, which we
estimate as 0.48 +/- 0.10 at z=0.32 and 0.30 +/- 0.07 at z=0.57, the latter
constituting the highest redshift at which this quantity has been determined.
These measurements are consistent with the predictions of General Relativity,
for a perturbed Friedmann-Robertson-Walker metric in a Universe dominated by a
cosmological constant, which are E_G = 0.41 and 0.36 at these respective
redshifts. The combination of redshift-space distortion and gravitational
lensing data from current and future galaxy surveys will offer increasingly
stringent tests of fundamental cosmology.Comment: 25 pages, 24 figures, version accepted for publication by MNRAS,
blind analysi
KiDS+2dFLenS+GAMA: Testing the cosmological model with the EG statistic
We present a new measurement of EG, which combines measurements of weak gravitational lensing, galaxy clustering, and redshift-space distortions. This statistic was proposed as a consistency test of General Relativity (GR) that is insensitive to linear, deterministic galaxy bias, and the matter clustering amplitude. We combine deep imaging data from KiDS with overlapping spectroscopy from 2dFLenS, BOSS DR12, and GAMA and find EG (z=0.267) = 0.43 ± 0.13(GAMA), EG (z=0.305) = 0.27 ± 0.08 (LOWZ+2dFLOZ), and EG (z=0.0554) = 0.26 ± 0.07 (CMASS + 2dFHIZ). We demonstrate that the existing tension in the value of the matter density parameter hinders the robustness of this statistic as solely a test of GR. We find that our EG measurements, as well as existing ones in the literature, favour a lower matter density cosmology than the cosmic microwave background. For a flat ÎCDM Universe, we find Ωm(z = 0) = 0.25 ± 0.03. With this paper, we publicly release the 2dFLenS data set at: http://2dflens.swin.edu.au.AA, CH, MA, and SJ acknowledge support from the European Research Council under grant numbers 647112 (CH and MA)
and 693024 (SJ). CB acknowledges the support of the Australian
Research Council through the award of a Future Fellowship. DL acknowledges support from the McWilliams Center for Cosmology,
Department of Physics, Carnegie Mellon University. HHi acknowledges support from an Emmy Noether grant (No. Hi 1495/2-1) of
the Deutsche Forschungsgemeinschaft. HHo acknowledges support
from Vici grant 639.043.512, financed by the Netherlands Organisation for Scientific Research (NWO). BJ acknowledges support by an
STFC Ernest Rutherford Fellowship, grant reference ST/J004421/1.
JHD acknowledges support from the EuropeansCommission under a Marie-Sklodwoska-Curie European Fellowship (EU project
656869). SJ also acknowledges support from the Beecroft Trust.
DP acknowledges the support of the Australian Research Council
through the award of a Future Fellowship. MB is supported by the
Netherlands Organisation for Scientific Research, NWO, through
grant number 614.001.45
RCSLenS: testing gravitational physics through the cross-correlation of weak lensing and large-scale structure
The unknown nature of âdark energyâ motivates continued cosmological tests of large-scale gravitational physics. We present a new consistency check based on the relative amplitude of non-relativistic galaxy peculiar motions, measured via redshift-space distortion, and the relativistic deflection of light by those same galaxies traced by galaxyâgalaxy lensing. We take advantage of the latest generation of deep, overlapping imaging and spectroscopic data sets, combining the Red Cluster Sequence Lensing Survey, the CanadaâFranceâHawaii Telescope Lensing Survey, the WiggleZ Dark Energy Survey and the Baryon Oscillation Spectroscopic Survey. We quantify the results using the âgravitational slipâ statistic EG, which we estimate as 0.48 ± 0.10 at z = 0.32 and 0.30 ± 0.07 at z = 0.57, the latter constituting the highest redshift at which this quantity has been determined. These measurements are consistent with the predictions of General Relativity, for a perturbed FriedmannâRobertsonâWalker metric in a Universe dominated by a cosmological constant, which are EG = 0.41 and 0.36 at these respective redshifts. The combination of redshift-space distortion and gravitational lensing data from current and future galaxy surveys will offer increasingly stringent tests of fundamental cosmology