scholarly journals Anisotropies of galaxy ellipticity correlations in real and redshift space: angular dependence in linear tidal alignment model

2020 ◽  
Vol 493 (1) ◽  
pp. L124-L128 ◽  
Author(s):  
Teppei Okumura ◽  
Atsushi Taruya
Keyword(s):  
Angular Dependence ◽  
Gravitational Lensing ◽  
Correlation Functions ◽  
Clustering Analysis ◽  
Cosmological Parameters ◽  
Line Of Sight ◽  
Acoustic Oscillations ◽  
Galaxy Clustering ◽  
Space Distortion ◽  
Alignment Model

ABSTRACT Investigating intrinsic alignments (IAs) of galaxy shapes is important not only to constrain cosmological parameters unbiasedly from gravitational lensing but also to extract cosmological information complimentary to galaxy clustering analysis. We derive simple and useful formulas for the various IA statistics, including the intrinsic ellipticity–ellipticity correlation, the gravitational shear–intrinsic ellipticity correlation, and the velocity–intrinsic ellipticity correlation functions. The angular dependence of each statistic is explicitly given, namely the angle between the line-of-sight direction and the separation vector of two points. It thus allows us to analyse anisotropies of baryon acoustic oscillations encoded in the IA statistics, and we can extract the maximum cosmological information using the Alcock–Paczynski and redshift-space distortion effects. We also provide these formulas for the intrinsic ellipticities decomposed into E and B modes.

scholarly journals Testing tidal alignment models for anisotropic correlations of halo ellipticities with N-body simulations

2020 ◽  
Vol 494 (1) ◽  
pp. 694-702 ◽  
Author(s):  
Teppei Okumura ◽  
Atsushi Taruya ◽  
Takahiro Nishimichi
Keyword(s):  
Dark Matter ◽  
Large Volume ◽  
Correlation Functions ◽  
Clustering Analysis ◽  
Large Scale ◽  
Acoustic Oscillations ◽  
Model Predictions ◽  
Alignment Model ◽  
Linear Alignment ◽  
Scale Limit

ABSTRACT There is a growing interest of using the intrinsic alignment (IA) of galaxy images as a tool to extract cosmological information complimentary to galaxy clustering analysis. Recently, Okumura & Taruya derived useful formulas for the intrinsic ellipticity–ellipticity correlation, the gravitational shear–intrinsic ellipticity correlation, and the velocity–intrinsic ellipticity correlation functions based on the linear alignment (LA) model. In this paper, using large-volume N-body simulations, we measure these alignment statistics for dark-matter haloes in real and redshift space and compare them to the LA and non-linear alignment model predictions. We find that anisotropic features of baryon acoustic oscillations in the IA statistics can be accurately predicted by our models. The anisotropy due to redshift-space distortions (RSDs) is also well described in the large-scale limit. Our results indicate that one can extract the cosmological information encoded in the IA through the Alcock–Paczynski and RSD effects.

scholarly journals Suppressing cosmic variance with paired-and-fixed cosmological simulations: average properties and covariances of dark matter clustering statistics

2020 ◽  
Vol 496 (3) ◽  
pp. 3862-3869 ◽  
Author(s):  
Anatoly Klypin ◽  
Francisco Prada ◽  
Joyce Byun
Keyword(s):  
Dark Matter ◽  
Power Spectrum ◽  
Initial Conditions ◽  
Cosmological Parameters ◽  
Average Density ◽  
Covariance Matrices ◽  
Acoustic Oscillations ◽  
Galaxy Clustering ◽  
The Mean ◽  
Statistical Noise

ABSTRACT Making cosmological inferences from the observed galaxy clustering requires accurate predictions for the mean clustering statistics and their covariances. Those are affected by cosmic variance – the statistical noise due to the finite number of harmonics. The cosmic variance can be suppressed by fixing the amplitudes of the harmonics instead of drawing them from a Gaussian distribution predicted by the inflation models. Initial realizations also can be generated in pairs with 180○ flipped phases to further reduce the variance. Here, we compare the consequences of using paired-and-fixed versus Gaussian initial conditions on the average dark matter clustering and covariance matrices predicted from N-body simulations. As in previous studies, we find no measurable differences between paired-and-fixed and Gaussian simulations for the average density distribution function, power spectrum, and bispectrum. Yet, the covariances from paired-and-fixed simulations are suppressed in a complicated scale- and redshift-dependent way. The situation is particularly problematic on the scales of Baryon acoustic oscillations where the covariance matrix of the power spectrum is lower by only $\sim 20{{\ \rm per\ cent}}$ compared to the Gaussian realizations, implying that there is not much of a reduction of the cosmic variance. The non-trivial suppression, combined with the fact that paired-and-fixed covariances are noisier than from Gaussian simulations, suggests that there is no path towards obtaining accurate covariance matrices from paired-and-fixed simulations – result, that is theoretically expected and accepted in the field. Because the covariances are crucial for the observational estimates of galaxy clustering statistics and cosmological parameters, paired-and-fixed simulations, though useful for some applications, cannot be used for the production of mock galaxy catalogues.

scholarly journals The Enhancement of BAO in the SDSS MGS

2015 ◽  
Vol 11 (S319) ◽  
pp. 145-145
Author(s):  
H. J. Tian ◽  
M. C. Neyrinck ◽  
T. Budavári ◽  
A. S. Szalay
Keyword(s):  
Correlation Functions ◽  
Line Of Sight ◽  
Acoustic Oscillations ◽  
Main Galaxy ◽  
Mexican Hat ◽  
Galaxy Sample ◽  
Baryon Acoustic Oscillations

AbstractWe show that redshift-space distortions of galaxy correlations have a strong effect on correlation functions with the signature of the Baryon Acoustic Oscillations (BAO). Near the line of sight, the features become sharper as a result of redshift-space distortions. We analyze the SDSS DR7 main-galaxy sample (MGS), splitting the sample into slices 2.5 deg on the sky in various rotations. Measuring 2D correlation functions in each slice, we do see a sharp bump along the line of sight. Using Mexican-hat wavelets, we localize it to (110 ± 10) h − 1 Mpc and estimate its significance at about 4σ.

scholarly journals Statistical separation of weak gravitational lensing and intrinsic ellipticities based on galaxy colour information

2020 ◽  
Vol 494 (2) ◽  
pp. 2969-2981 ◽  
Author(s):  
Tim M Tugendhat ◽  
Robert Reischke ◽  
Björn Malte Schäfer
Keyword(s):  
Parameter Estimation ◽  
Gravitational Lensing ◽  
Correlation Functions ◽  
Weak Lensing ◽  
Model Parameters ◽  
Linear Combinations ◽  
Statistical Separation ◽  
Cent Level ◽  
Model Independent ◽  
Alignment Model

ABSTRACT Intrinsic alignments of galaxies are recognized as one of the most important systematic in weak lensing surveys on small angular scales. In this paper, we investigate ellipticity correlation functions that are measured separately on elliptical and spiral galaxies, for which we assume the generic alignment mechanisms based on tidal shearing and tidal torquing, respectively. Including morphological information allows to find linear combinations of measured ellipticity correlation functions that suppress the gravitational lensing signal completely or which show a strongly boosted gravitational lensing signal relative to intrinsic alignments. Specifically, we find that (i) intrinsic alignment spectra can be measured in a model-independent way at a significance of Σ ≃ 60 with a wide-angle tomographic survey such as Euclid’s, (ii) the underlying intrinsic alignment model parameters can be determined at per cent-level precision, (iii) this measurement is not impeded by misclassifying galaxies and assuming a wrong alignment model, (iv) parameter estimation from a cleaned weak lensing spectrum is possible with almost no bias, and (v) the misclassification would not strongly impact parameter estimation from the boosted weak lensing spectrum.

scholarly journals Cosmological constraints on the neutrino mass including systematic uncertainties

2017 ◽  
Vol 606 ◽  
pp. A104 ◽  
Author(s):  
F. Couchot ◽  
S. Henrot-Versillé ◽  
O. Perdereau ◽  
S. Plaszczynski ◽  
B. Rouillé d’Orfeuil ◽  
...  
Keyword(s):  
Neutrino Mass ◽  
Gravitational Lensing ◽  
Cosmological Parameters ◽  
Acoustic Oscillations ◽  
Inverted Hierarchy ◽  
Neutrino Sector ◽  
Systematic Uncertainties ◽  
Λcdm Model ◽  
Type Ia ◽  
The Impact

When combining cosmological and oscillations results to constrain the neutrino sector, the question of the propagation of systematic uncertainties is often raised. We address this issue in the context of the derivation of an upper bound on the sum of the neutrino masses (Σmν) with recent cosmological data. This work is performed within the ΛCDM model extended to Σmν, for which we advocate the use of three mass-degenerate neutrinos. We focus on the study of systematic uncertainties linked to the foregrounds modelling in cosmological microwave background (CMB) data analysis, and on the impact of the present knowledge of the reionisation optical depth. This is done through the use of different likelihoods built from Planck data. Limits on Σmν are derived with various combinations of data, including the latest baryon acoustic oscillations (BAO) and Type Ia supernovae (SNIa) results. We also discuss the impact of the preference for current CMB data for amplitudes of the gravitational lensing distortions higher than expected within the ΛCDM model, and add the Planck CMB lensing. We then derive a robust upper limit: Σmν< 0.17 eV at 95% CL, including 0.01eV of foreground systematics. We also discuss the neutrino mass repartition and show that today’s data do not allow one to disentangle normal from inverted hierarchy. The impact on the other cosmological parameters is also reported, for different assumptions on the neutrino mass repartition, and different high and low multipole CMB likelihoods.

scholarly journals Mapping dark matter and finding filaments: calibration of lensing analysis techniques on simulated data

2020 ◽  
Vol 496 (3) ◽  
pp. 3973-3990
Author(s):  
Sut-Ieng Tam ◽  
Richard Massey ◽  
Mathilde Jauzac ◽  
Andrew Robertson
Keyword(s):  
Gravitational Lensing ◽  
Simulated Data ◽  
Line Of Sight ◽  
Radial Density ◽  
Density Profiles ◽  
Analysis Techniques ◽  
Scientific Goal ◽  
Mass Mapping ◽  
Mapping Techniques ◽  
Suppress Noise

ABSTRACT We quantify the performance of mass mapping techniques on mock imaging and gravitational lensing data of galaxy clusters. The optimum method depends upon the scientific goal. We assess measurements of clusters’ radial density profiles, departures from sphericity, and their filamentary attachment to the cosmic web. We find that mass maps produced by direct (KS93) inversion of shear measurements are unbiased, and that their noise can be suppressed via filtering with mrlens. Forward-fitting techniques, such as lenstool, suppress noise further, but at a cost of biased ellipticity in the cluster core and overestimation of mass at large radii. Interestingly, current searches for filaments are noise-limited by the intrinsic shapes of weakly lensed galaxies, rather than by the projection of line-of-sight structures. Therefore, space-based or balloon-based imaging surveys that resolve a high density of lensed galaxies could soon detect one or two filaments around most clusters.

scholarly journals MACS J0416.1–2403: Impact of line-of-sight structures on strong gravitational lensing modelling of galaxy clusters

2018 ◽  
Vol 614 ◽  
pp. A8 ◽  
Author(s):  
G. Chirivì ◽  
S. H. Suyu ◽  
C. Grillo ◽  
A. Halkola ◽  
I. Balestra ◽  
...  
Keyword(s):  
Galaxy Clusters ◽  
Gravitational Lensing ◽  
Line Of Sight ◽  
Mass Distributions ◽  
Strong Gravitational Lensing ◽  
Cluster Mass ◽  
Critical Curves ◽  
Single Lens ◽  
Best Fitting ◽  
Modelling Techniques

Exploiting the powerful tool of strong gravitational lensing by galaxy clusters to study the highest-redshift Universe and cluster mass distributions relies on precise lens mass modelling. In this work, we aim to present the first attempt at modelling line-of-sight (LOS) mass distribution in addition to that of the cluster, extending previous modelling techniques that assume mass distributions to be on a single lens plane. We have focussed on the Hubble Frontier Field cluster MACS J0416.1–2403, and our multi-plane model reproduces the observed image positions with a rms offset of ~0.′′53. Starting from this best-fitting model, we simulated a mock cluster that resembles MACS J0416.1–2403 in order to explore the effects of LOS structures on cluster mass modelling. By systematically analysing the mock cluster under different model assumptions, we find that neglecting the lensing environment has a significant impact on the reconstruction of image positions (rms ~0.′′3); accounting for LOS galaxies as if they were at the cluster redshift can partially reduce this offset. Moreover, foreground galaxies are more important to include into the model than the background ones. While the magnification factor of the lensed multiple images are recovered within ~10% for ~95% of them, those ~5% that lie near critical curves can be significantly affected by the exclusion of the lensing environment in the models. In addition, LOS galaxies cannot explain the apparent discrepancy in the properties of massive sub-halos between MACS J0416.1–2403 and N-body simulated clusters. Since our model of MACS J0416.1–2403 with LOS galaxies only reduced modestly the rms offset in the image positions, we conclude that additional complexities would be needed in future models of MACS J0416.1–2403.

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