427 research outputs found
Fast computation of non-linear power spectrum in cosmologies with massive neutrinos
We compute 1-loop corrections to the redshift space galaxy power spectrum in
cosmologies containing additional scales, and hence kernels different from
Einstein-de Sitter (EdS). Specifically, our method is tailored for cosmologies
in the presence of massive neutrinos and some modified gravity models; in this
article we concentrate on the former case. The perturbative kernels have
contributions that we notice appear either from the logarithmic growth factor
, which is scale-dependent because of the neutrino free-streaming, or
from the failure of the commonly used approximation . The latter
contributions make the computation of loop corrections quite slow, precluding
full-shape analyses for parameter estimation. However, we identify that the
dominant pieces of the kernels come from the growth factor, allowing us to
simplify the kernels but retaining the characteristic free-streaming scale
introduced by the neutrinos' mass. Moreover, with this simplification one can
exploit FFTLog methods to speed up the computations even more. We validate our
analytical modeling and numerical method with halo catalogs extracted from the
Quijote simulations finding good agreement with the, a priori, known
cosmological parameters. We make public our Python code FOLPS to compute
the redshift space power spectrum in a fraction of second. Code available at
https://github.com/henoriega/FOLPS-nu.Comment: 38 pages + appendices, 13 figures. v2: Adds fits at redshift z=
Full Shape Cosmology Analysis from BOSS in configuration space using Neural Network Acceleration
Recently, a new wave of full modeling analyses have emerged within the
Large-Scale Structure community, leading mostly to tighter constraints on the
estimation of cosmological parameters, when compared with standard approaches
used over the last decade by collaboration analyses of stage III experiments.
However, the majority of these full-shape analyses have primarily been
conducted in Fourier space, with limited emphasis on exploring the
configuration space. Investigating n-point correlations in configuration space
demands a higher computational cost compared to Fourier space because it
typically requires an additional integration step. This can pose a limitation
when using these approaches, especially when considering higher-order
statistics. One avenue to mitigate the high computation time is to take
advantage of neural network acceleration techniques. In this work, we present a
full shape analysis of Sloan Digital Sky Survey III/BOSS in configuration space
using a neural network accelerator. We show that the efficacy of the pipeline
is enhanced by a time factor without sacrificing precision, making it
possible to reduce the error associated with the surrogate modeling to below
percent which is compatible with the precision required for current
stage IV experiments such as DESI. We find ,
and . Our results on public BOSS data are in
good agreement with BOSS official results and compatible with other independent
full modeling analyses. We explore relaxing the prior on and varying
, without significant changes in the mean values of the cosmological
parameters posterior distributions, but enlarging their widths. Finally, we
explore the information content of the multipoles when constraining
cosmological parameters
fkPT: constraining scale-dependent modified gravity with the full-shape galaxy power spectrum
Modified gravity models with scale-dependent linear growth typically exhibit an enhancement in the power spectrum beyond a certain scale. The conventional methods for extracting cosmological information usually involve inferring modified gravity effects via Redshift Space Distortions (RSD), particularly through the time evolution of fσ 8. However, classical galaxy RSD clustering analyses encounter difficulties in accurately capturing the spectrum's enhanced power, which is better obtained from the broad-band power spectrum. In this sense, full-shape analyses aim to consider survey data using comprehensive and precise models of the whole power spectrum. Yet, a major challenge in this approach is the slow computation of non-linear loop integrals for scale-dependent modified gravity, precluding the estimation of cosmological parameters using Markov Chain Monte Carlo methods. Based on recent studies, in this work we develop a perturbation theory tailored for Modified Gravity, or analogous scenarios introducing additional scales, such as in the presence of massive neutrinos. Our approach only needs the calculation of the scale-dependent growth rate f(k,t) and the limit of the perturbative kernels at large scales. We called this approximate technique as fk-Perturbation Theory and implemented it into the code fkpt, capable of computing the redshift space galaxy power spectrum in a fraction of a second. We validate our modeling and code with the f(R) theory MG-GLAM and General Relativity NSeries sets of simulations. The code is available at https://github.com/alejandroaviles/fkpt
Detection of Baryon Acoustic Oscillation Features in the Large-Scale 3-Point Correlation Function of SDSS BOSS DR12 CMASS Galaxies
We present the large-scale 3-point correlation function (3PCF) of the SDSS
DR12 CMASS sample of Luminous Red Galaxies, the largest-ever sample
used for a 3PCF or bispectrum measurement. We make the first high-significance
() detection of Baryon Acoustic Oscillations (BAO) in the 3PCF.
Using these acoustic features in the 3PCF as a standard ruler, we measure the
distance to to precision (statistical plus systematic). We
find for our
fiducial cosmology (consistent with Planck 2015) and bias model. This
measurement extends the use of the BAO technique from the 2-point correlation
function (2PCF) and power spectrum to the 3PCF and opens an avenue for deriving
additional cosmological distance information from future large-scale structure
redshift surveys such as DESI. Our measured distance scale from the 3PCF is
fairly independent from that derived from the pre-reconstruction 2PCF and is
equivalent to increasing the length of BOSS by roughly 10\%; reconstruction
appears to lower the independence of the distance measurements. Fitting a model
including tidal tensor bias yields a moderate significance (
detection of this bias with a value in agreement with the prediction from local
Lagrangian biasing.Comment: 15 pages, 7 figures, submitted MNRA
Efficient reconstruction of linear baryon acoustic oscillations in galaxy surveys
Reconstructing an estimate of linear baryon acoustic oscillations (BAO) from an evolved galaxy field has become a standard technique in recent analyses. By partially removing non-linear damping caused by bulk motions, the real-space BAO peak in the correlation function is sharpened, and oscillations in the power spectrum are visible to smaller scales. In turn these lead to stronger measurements of the BAO scale. Future surveys are being designed assuming that this improvement has been applied, and this technique is therefore of critical importance for future BAO measurements. A number of reconstruction techniques are available, but the most widely used is a simple algorithm that decorrelates large-scale and small-scale modes approximately removing the bulk-flow displacements by moving the overdensity field. We consider the practical implementation of this algorithm, looking at the efficiency of reconstruction as a function of the assumptions made for the bulk-flow scale, the shot-noise level in a random catalogue used to quantify the mask and the method used to estimate the bulk-flow shifts. We also examine the efficiency of reconstruction against external factors including galaxy density, volume and edge effects, and consider their impact for future surveys. Throughout we make use of the mocks catalogues created for the Baryon Oscillation Spectroscopic Survey (BOSS) Date Release 11 samples covering 0.43 < z < 0.7 (CMASS) and 0.15 < z < 0.43 (LOWZ), to empirically test these changes
First constraint on the neutrino-induced phase shift in the spectrum of baryon acoustic oscillations
The existence of the cosmic neutrino background is a robust prediction of the hot big bang model. These neutrinos were a dominant component of the energy density in the early universe and, therefore, played an important role in the evolution of cosmological perturbations. The energy density of the cosmic neutrino background has been measured using the abundances of light elements and the anisotropies of the cosmic microwave background. A complementary and more robust probe is a distinct shift in the temporal phase of sound waves in the primordial plasma which is produced by fluctuations in the neutrino density. In this Article, we report on the first constraint on this neutrino-induced phase shift in the spectrum of baryon acoustic oscillations of the BOSS DR12 data. Constraining the acoustic scale using Planck data while marginalizing over the effects of neutrinos in the cosmic microwave background, we find a non-zero phase shift at greater than 95% confidence. Besides providing a new test of the cosmic neutrino background, our work is the first application of the baryon acoustic oscillation signal to early universe physics
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