scholarly journals Dark Energy Survey Year 1 results: measurement of the galaxy angular power spectrum

2019 ◽  
Vol 487 (3) ◽  
pp. 3870-3883 ◽  
Author(s):  
H Camacho ◽  
N Kokron ◽  
F Andrade-Oliveira ◽  
R Rosenfeld ◽  
M Lima ◽  
...  
Keyword(s):  
Power Spectrum ◽  
Covariance Matrix ◽  
Goodness Of Fit ◽  
Effective Area ◽  
Real Space ◽  
Harmonic Space ◽  
Angular Power Spectrum ◽  
Space Analysis ◽  
The Galaxy ◽  
The Impact

ABSTRACT We use data from the first-year observations of the DES collaboration to measure the galaxy angular power spectrum (APS), and search for its BAO feature. We test our methodology in a sample of 1800 DES Y1-like mock catalogues. We use the pseudo-Cℓ method to estimate the APS and the mock catalogues to estimate its covariance matrix. We use templates to model the measured spectra and estimate template parameters firstly from the Cℓ’s of the mocks using two different methods, a maximum likelihood estimator and a Markov Chain Monte Carlo, finding consistent results with a good reduced χ2. Robustness tests are performed to estimate the impact of different choices of settings used in our analysis. Finally, we apply our method to a galaxy sample constructed from DES Y1 data specifically for LSS studies. This catalogue comprises galaxies within an effective area of 1318 deg2 and 0.6 < z < 1.0. We find that the DES Y1 data favour a model with BAO at the $2.6 \sigma$ C.L. However, the goodness of fit is somewhat poor, with χ2/(d.o.f.)  = 1.49. We identify a possible cause showing that using a theoretical covariance matrix obtained from Cℓ’s that are better adjusted to data results in an improved value of χ2/(dof)  = 1.36 which is similar to the value obtained with the real-space analysis. Our results correspond to a distance measurement of DA(zeff = 0.81)/rd = 10.65 ± 0.49, consistent with the main DES BAO findings. This is a companion paper to the main DES BAO article showing the details of the harmonic space analysis.

scholarly journals An Accurate Reconstruction of CMB E Mode Signal over Large Angular Scales using Prior Information of CMB Covariance Matrix in ILC Algorithm

2020 ◽  
Author(s):  
Ujjal Purkayastha ◽  
Vipin Sudevan ◽  
Rajib Saha
Keyword(s):  
Power Spectrum ◽  
Linear Combination ◽  
Covariance Matrix ◽  
Large Scale ◽  
Prior Information ◽  
Future Generation ◽  
Temperature Anisotropy ◽  
Satellite Mission ◽  
Angular Power Spectrum ◽  
Accurate Reconstruction

Abstract Recently, the internal-linear-combination (ILC) method was investigated extensively in the context of reconstruction of Cosmic Microwave Background (CMB) temperature anisotropy signal using observations obtained by WMAP and Planck satellite missions. In this article, we, for the first time, apply the ILC method to reconstruct the large scale CMB E mode polarization signal, which could probe the ionization history, using simulated observations of 15 frequency CMB polarization maps of future generation Cosmic Origin Explorer (COrE) satellite mission. We find that the clean power spectra, from the usual ILC, are strongly biased due to non zero CMB-foregrounds chance correlations. In order to address the issues of bias and errors we extend and improve the usual ILC method for CMB E mode reconstruction by incorporating prior information of theoretical E mode angular power spectrum while estimating the weights for linear combination of input maps (Sudevan & Saha 2018b). Using the E mode covariance matrix effectively suppresses the CMB-foreground chance correlation power leading to an accurate reconstruction of cleaned CMB E mode map and its angular power spectrum. We compare the performance of the usual ILC and the new method over large angular scales and show that the later produces significantly statistically improved results than the former. The new E mode CMB angular power spectrum contains neither any significant negative bias at the low multipoles nor any positive foreground bias at relatively higher mutlipoles. The error estimates of the cleaned spectrum agree very well with the cosmic variance induced error.

scholarly journals Impact of relativistic effects on the primordial non-Gaussianity signature in the large-scale clustering of quasars

2020 ◽  
Vol 499 (2) ◽  
pp. 2598-2607
Author(s):  
Mike (Shengbo) Wang ◽  
Florian Beutler ◽  
David Bacon
Keyword(s):  
Dark Energy ◽  
Power Spectrum ◽  
Luminosity Function ◽  
Large Scale ◽  
Relativistic Effects ◽  
Redshift Range ◽  
Cosmological Background ◽  
Relativistic Corrections ◽  
The Galaxy ◽  
The Impact

ABSTRACT Relativistic effects in clustering observations have been shown to introduce scale-dependent corrections to the galaxy overdensity field on large scales, which may hamper the detection of primordial non-Gaussianity fNL through the scale-dependent halo bias. The amplitude of relativistic corrections depends not only on the cosmological background expansion, but also on the redshift evolution and sensitivity to the luminosity threshold of the tracer population being examined, as parametrized by the evolution bias be and magnification bias s. In this work, we propagate luminosity function measurements from the extended Baryon Oscillation Spectroscopic Survey (eBOSS) to be and s for the quasar (QSO) sample, and thereby derive constraints on relativistic corrections to its power spectrum multipoles. Although one could mitigate the impact on the fNL signature by adjusting the redshift range or the luminosity threshold of the tracer sample being considered, we suggest that, for future surveys probing large cosmic volumes, relativistic corrections should be forward modelled from the tracer luminosity function including its uncertainties. This will be important to quasar clustering measurements on scales $k \sim 10^{-3}\, h\, {\rm Mpc}^{-1}$ in upcoming surveys such as the Dark Energy Spectroscopic Instrument (DESI), where relativistic corrections can overwhelm the expected fNL signature at low redshifts z ≲ 1 and become comparable to fNL ≃ 1 in the power spectrum quadrupole at redshifts z ≳ 2.5.

scholarly journals Generating approximate halo catalogues for blind challenges in precision cosmology

2019 ◽  
Vol 485 (2) ◽  
pp. 2407-2416 ◽  
Author(s):  
Lehman H Garrison ◽  
Daniel J Eisenstein
Keyword(s):  
Dark Matter ◽  
Transfer Function ◽  
Power Spectrum ◽  
High Precision ◽  
Real Space ◽  
Dark Matter Halo ◽  
The Real ◽  
The Galaxy ◽  
Similar Accuracy ◽  
Better Than

ABSTRACT We present a method for generating suites of dark matter halo catalogues with only a few N-body simulations, focusing on making small changes to the underlying cosmology of a simulation with high precision. In the context of blind challenges, this allows us to re-use a simulation by giving it a new cosmology after the original cosmology is revealed. Starting with full N-body realizations of an original cosmology and a target cosmology, we fit a transfer function that displaces haloes in the original so that the galaxy/HOD power spectrum matches that of the target cosmology. This measured transfer function can then be applied to a new realization of the original cosmology to create a new realization of the target cosmology. For a 1 per cent change in σ8, we achieve 0.1 per cent accuracy to $k = 1\, h\, \mathrm{Mpc}^{-1}$ in the real-space power spectrum; this degrades to 0.3 per cent when the transfer function is applied to a new realization. We achieve similar accuracy in the redshift-space monopole and quadrupole. In all cases, the result is better than the sample variance of our $1.1\, h^{-1}\, \mathrm{Gpc}$ simulation boxes.

scholarly journals Understanding the impact of Light cone effect on the EoR/CD 21-cm power spectrum

2017 ◽  
Vol 12 (S333) ◽  
pp. 12-17
Author(s):  
Kanan K. Datta ◽  
Rajesh Mondal ◽  
Raghunath Ghara ◽  
Somnath Bharadwaj ◽  
T. Roy Choudhury
Keyword(s):  
Power Spectrum ◽  
Order Statistics ◽  
Light Cone ◽  
Second Order ◽  
Line Of Sight ◽  
Periodic Signal ◽  
Angular Power Spectrum ◽  
Second Order Statistics ◽  
The Impact

AbstractRedshifted HI 21-cm signal from the cosmic dawn and epoch of reionization evolve considerably along the LoS. We study the impact of this evolution (so called the light cone effect) on the HI 21-cm power spectrum. It is found that the LC effect has a significant impact on the 3D power spectrum and the change could be up to a factor of few. The LC effect is particularly strong during the cosmic dawn near the ‘peaks’ and ‘dips’ in the power spectrum when plotted with redshift. We also show that the 3D power spectrum, which could fully describe ergodic and periodic signal, losses out some information regarding the second order statistics of the signal as the EoR/CD 21-cm signal is non-ergodic and non-periodic along the line of sight. We show that the multi-frequency angular power spectrum (MAPS)${\mathcal {C}}_{\ell }(\nu _1, \nu _2)$captures all the information regarding the second order statistics of the signal even in the presence of the LC effect.

scholarly journals Cosmological parameters from the likelihood analysis of the galaxy power spectrum and bispectrum in real space

2021 ◽  
Vol 2021 (11) ◽  
pp. 038
Author(s):  
Andrea Oddo ◽  
Federico Rizzo ◽  
Emiliano Sefusatti ◽  
Cristiano Porciani ◽  
Pierluigi Monaco
Keyword(s):  
Power Spectrum ◽  
Cosmological Parameters ◽  
Deviance Information Criterion ◽  
Information Criterion ◽  
Real Space ◽  
Tree Level ◽  
Large Set ◽  
Cross Covariance ◽  
Likelihood Analysis ◽  
The Galaxy

Abstract We present a joint likelihood analysis of the halo power spectrum and bispectrum in real space. We take advantage of a large set of numerical simulations and of an even larger set of halo mock catalogs to provide a robust estimate of the covariance properties. We derive constraints on bias and cosmological parameters assuming a theoretical model from perturbation theory at one-loop for the power spectrum and tree-level for the bispectrum. By means of the Deviance Information Criterion, we select a reference bias model dependent on seven parameters that can describe the data up to k max,P = 0.3 h Mpc-1 for the power spectrum and k max,B = 0.09 h Mpc-1 for the bispectrum at redshift z = 1. This model is able to accurately recover three selected cosmological parameters even for the rather extreme total simulation volume of 1000h -3 Gpc3. With the same tools, we study how relations among bias parameters can improve the fit while reducing the parameter space. In addition, we compare common approximations to the covariance matrix against the full covariance estimated from the mocks, and quantify the (non-negligible) effect of ignoring the cross-covariance between the two statistics. Finally, we explore different selection criteria for the triangular configurations to include in the analysis, showing that excluding nearly equilateral triangles rather than simply imposing a fixed maximum k max,B on all triangle sides can lead to a better exploitation of the information contained in the bispectrum.

scholarly journals Contributions from primordial non-Gaussianity and general relativity to the galaxy power spectrum

2021 ◽  
Vol 2021 (12) ◽  
pp. 025
Author(s):  
Rebeca Martinez-Carrillo ◽  
Juan Carlos Hidalgo ◽  
Karim A. Malik ◽  
Alkistis Pourtsidou
Keyword(s):  
General Relativity ◽  
Power Spectrum ◽  
Stage Iv ◽  
Real Space ◽  
Order Effects ◽  
Leading Order ◽  
Bias Parameter ◽  
Matter Power Spectrum ◽  
The Galaxy ◽  
The One

Abstract We compute the real space galaxy power spectrum, including the leading order effects of General Relativity and primordial non-Gaussianity from the f NL and g NL parameters. Such contributions come from the one-loop matter power spectrum terms dominant at large scales, and from the factors of the non-linear bias parameter b NL (akin to the Newtonian b ϕ). We assess the detectability of these contributions in Stage-IV surveys. In particular, we note that specific values of the bias parameter may erase the primordial and relativistic contributions to the configuration space power spectrum.

scholarly journals Covariance of the galaxy angular power spectrum with the halo model

2018 ◽  
Vol 615 ◽  
pp. A1 ◽  
Author(s):  
Fabien Lacasa
Keyword(s):  
Perturbation Theory ◽  
Shot Noise ◽  
Real Space ◽  
Density Fluctuations ◽  
Tree Level ◽  
Analytical Prediction ◽  
Angular Power Spectrum ◽  
Sample Covariance ◽  
The Galaxy ◽  
Non Gaussian

As the determination of density fluctuations becomes more precise with larger surveys, it becomes more important to account for the increased covariance due to the non-linearity of the field. Here I have focussed on the galaxy density, with analytical prediction of the non-Gaussianity using the halo model coupled with standard perturbation theory in real space. I carried out an exact and exhaustive derivation of all tree-level terms of the non-Gaussian covariance of the galaxyCℓ, with the computation developed up to the third order in perturbation theory and local halo bias, including the non-local tidal tensor effect. A diagrammatic method was used to derive the involved galaxy 3D trispectra, including shot-noise contributions. The projection to the angular covariance was derived in all trispectra cases with and without Limber’s approximation, with the formulae being of potential interest for other observables than galaxies. The effect of subtracting shot-noise from the measured spectrum is also discussed, and does simplify the covariance, though some non-Gaussian shot-noise terms still remain. I make the link between this complete derivation and partial terms which have been used previously in the literature, including super-sample covariance (SSC). I uncover a wealth of additional terms which were not previously considered, including a whole new class which I dub braiding terms as it contains multipole-mixing kernels. The importance of all these new terms is discussed with analytical arguments. I find that they become comparable to, if not bigger than, SSC if the survey is large or deep enough to probe scales comparable with the matter-radiation equalitykeq. A short self-contained summary of the equations is provided in Sect. 9 for the busy reader, ready to be implemented numerically for analysis of current and future galaxy surveys.

scholarly journals Gravitational Fluctuations as an Alternative to Inflation II. CMB Angular Power Spectrum

2019 ◽  
Author(s):  
Herbert W. Hamber ◽  
Lu Heng Sunny Yu
Keyword(s):  
Power Spectrum ◽  
Power Spectra ◽  
Angular Spectrum ◽  
Scalar Fields ◽  
Data Sets ◽  
Angular Power Spectrum ◽  
Fundamental Parameters ◽  
Matter Power Spectrum ◽  
The Galaxy ◽  
Cosmological Data

Power spectra always play an important role in the theory of inflation. In particular, the ability to reproduce the galaxy matter power spectrum $ P(k) $ and the CMB temperature angular power spectrum $ C_l $’s to high accuracy is often considered a triumph of inflation. In our previous work, we presented an alternative explanation for the matter power spectrum based on nonperturbative quantum field-theoretical methods applied to Einstein’s gravity, instead of inflation models based on scalar fields. In this work, we review the basic concepts and provide further in-depth investigations. We first update the analysis with more recent data sets and error analysis, and then extend our predictions to the CMB angular spectrum coefficients $ C_l $, which we did not consider previously. Then we investigate further the potential freedoms and uncertainties associated with the fundamental parameters that are part of this picture, and show how recent cosmological data provides significant constraints on these quantities. Overall, we find good general consistency between theory and data, even potentially favoring the gravitationally-motivated picture at the largest scales. We summarize our results by outlining how this picture can be tested in the near future with increasingly accurate astrophysical measurements.

scholarly journals Impact of photometric redshifts on the galaxy power spectrum and BAO scale in the LSST survey

2019 ◽  
Vol 623 ◽  
pp. A76 ◽  
Author(s):  
Reza Ansari ◽  
Adeline Choyer ◽  
Farhang Habibi ◽  
Christophe Magneville ◽  
Marc Moniez ◽  
...  
Keyword(s):  
Power Spectrum ◽  
Large Scale ◽  
Near Infrared ◽  
Linear Part ◽  
Cosmological Parameters ◽  
Photometric Redshifts ◽  
Photometric Redshift ◽  
Near Ultraviolet ◽  
The Galaxy ◽  
The Impact

Context. The Large Synoptic Survey Telescope (LSST) survey will image billions of galaxies every few nights for ten years, and as such, should be a major contributor to precision cosmology in the 2020s. High precision photometric data will be available in six bands, from near-infrared to near-ultraviolet. The computation of precise, unbiased, photometric redshifts up to at least z = 2 is one of the main LSST challenges and its performance will have major impact on all extragalactic LSST sciences. Aims. We evaluate the efficiency of our photometric redshift reconstruction on mock galaxy catalogues up to z = 2.45 and estimate the impact of realistic photometric redshift (photo-z) reconstruction on the large-scale structures (LSS) power spectrum and the baryonic acoustic oscillation (BAO) scale determination for a LSST-like photometric survey. We study the effectiveness of the BAO scale as a cosmological probe in the LSST survey. Methods. We have performed a detailed modelling of the photo-z distribution as a function of galaxy type, redshift and absolute magnitude using our photo-z reconstruction code with a quality selection cut based on a boosted decision tree (BDT). We have simulated a catalogue of galaxies in the redshift range [0.2−2.45] using the Planck 2015 ΛCDM cosmological parameters over 10 000 square-degrees, in the six bands, assuming LSST photometric precision for a ten-year survey. The mock galaxy catalogues were produced with several redshift error models. The LSS power spectrum was then computed in several redshift ranges and for each error model. Finally we extracted the BAO scale and its uncertainty using only the linear part of the LSS spectrum. Results. We have computed the fractional error on the recovered power spectrum which is dominated by the shot noise at high redshift (z ≳ 1), for scales k ≳ 0.1, due to the photo-z damping. The BAO scale can be recovered with a percent or better accuracy level from z = 0.5 to z = 1.5 using realistic photo-z reconstruction. Conclusions. Reaching the LSST requirements for photo-z reconstruction is crucial to exploit the LSST potential in cosmology, in particular to measure the LSS power spectrum and its evolution with redshift. Although the BAO scale is not the most powerful cosmological probe in LSST, it can be used to check the consistency of the LSS measurement. Moreover we show that the impact of photo-z smearing on the recovered isotropic BAO scale in LSST should stay limited up to z ≈ 1.5, so as long as the galaxy number density balances the photo-z smoothing.

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