scholarly journals Improvements in cosmological constraints from breaking growth degeneracy

2020 ◽  
Vol 642 ◽  
pp. A116
Author(s):  
L. Perenon ◽  
S. Ilić ◽  
R. Maartens ◽  
A. de la Cruz-Dombriz
Keyword(s):  
Large Scale ◽  
Cosmological Parameters ◽  
Cosmological Models ◽  
Gravity Models ◽  
Neutrino Masses ◽  
Cosmological Constraints ◽  
Correlation Spectrum ◽  
The Galaxy ◽  
Galaxy Sample ◽  
Standard Cosmological Model

Context. The key probes of the growth of a large-scale structure are its rate f and amplitude σ8. Redshift space distortions in the galaxy power spectrum allow us to measure only the combination fσ8, which can be used to constrain the standard cosmological model or alternatives. By using measurements of the galaxy-galaxy lensing cross-correlation spectrum or of the galaxy bispectrum, it is possible to break the fσ8 degeneracy and obtain separate estimates of f and σ8 from the same galaxy sample. Currently there are very few such separate measurements, but even this allows for improved constraints on cosmological models. Aims. We explore how having a larger and more precise sample of such measurements in the future could constrain further cosmological models. Methods. We considered what can be achieved by a future nominal sample that delivers an ∼1% constraint on f and σ8 separately, compared to the case with a similar precision on the combination fσ8. Results. For the six cosmological parameters of ΛCDM, we find improvements of ∼5–50% on their constraints. For modified gravity models in the Horndeski class, the improvements on these standard parameters are ∼0–15%. However, the precision on the sum of neutrino masses improves by 65% and there is a significant increase in the precision on the background and perturbation Horndeski parameters.

scholarly journals Can assembly bias explain the lensing amplitude of the BOSS CMASS sample in a Planck cosmology?

2020 ◽  
Vol 493 (4) ◽  
pp. 5551-5564
Author(s):  
Sihan Yuan ◽  
Daniel J Eisenstein ◽  
Alexie Leauthaud
Keyword(s):  
Cold Dark Matter ◽  
Cosmological Parameters ◽  
Bias Parameter ◽  
Projected Clustering ◽  
The Galaxy ◽  
Satellite Velocity ◽  
Galaxy Sample ◽  
Best Fitting ◽  
Galaxy Assembly ◽  
Halo Occupation Distribution

ABSTRACT In this paper, we investigate whether galaxy assembly bias can reconcile the 20–40 ${{\ \rm per\ cent}}$ disagreement between the observed galaxy projected clustering signal and the galaxy–galaxy lensing signal in the Baryon Oscillation Spectroscopic Survey CMASS galaxy sample. We use the suite of abacuscosmos lambda cold dark matter simulations at Planck best-fitting cosmology and two flexible implementations of extended halo occupation distribution (HOD) models that incorporate galaxy assembly bias to build forward models and produce joint fits of the observed galaxy clustering signal and the galaxy–galaxy lensing signal. We find that our models using the standard HODs without any assembly bias generalizations continue to show a 20–40 ${{\ \rm per\ cent}}$ overprediction of the observed galaxy–galaxy lensing signal. We find that our implementations of galaxy assembly bias do not reconcile the two measurements at Planck best-fitting cosmology. In fact, despite incorporating galaxy assembly bias, the satellite distribution parameter, and the satellite velocity bias parameter into our extended HOD model, our fits still strongly suggest a $\sim \! 34{{\ \rm per\ cent}}$ discrepancy between the observed projected clustering and galaxy–galaxy lensing measurements. It remains to be seen whether a combination of other galaxy assembly bias models, alternative cosmological parameters, or baryonic effects can explain the amplitude difference between the two signals.

scholarly journals Constraints on neutrino masses from the study of the nearby large-scale structure and galaxy cluster counts

2016 ◽  
Vol 31 (21) ◽  
pp. 1640008 ◽  
Author(s):  
Hans Böhringer ◽  
Gayoung Chon
Keyword(s):  
Large Scale ◽  
Cosmological Parameters ◽  
Large Scale Structure ◽  
Matter Density ◽  
Density Fluctuations ◽  
Scale Structure ◽  
Neutrino Masses ◽  
Microwave Background ◽  
X Ray ◽  
Massive Neutrinos

The high precision measurements of the cosmic microwave background by the Planck survey yielded tight constraints on cosmological parameters and the statistics of the density fluctuations at the time of recombination. This provides the means for a critical study of structure formation in the Universe by comparing the microwave background results with present epoch measurements of the cosmic large-scale structure. It can reveal subtle effects such as how different forms of Dark Matter may modify structure growth. Currently most interesting is the damping effect of structure growth by massive neutrinos. Different observations of low redshift matter density fluctuations provided evidence for a signature of massive neutrinos. Here we discuss the study of the cosmic large-scale structure with a complete sample of nearby, X-ray luminous clusters from our REFLEX cluster survey. From the observed X-ray luminosity function and its reproduction for different cosmological models, we obtain tight constraints on the cosmological parameters describing the matter density, [Formula: see text], and the density fluctuation amplitude, [Formula: see text]. A comparison of these constraints with the Planck results shows a discrepancy in the framework of a pure [Formula: see text]CDM model, but the results can be reconciled, if we allow for a neutrino mass in the range of 0.17 eV to 0.7 eV. Also some others, but not all of the observations of the nearby large-scale structure provide evidence or trends for signatures of massive neutrinos. With further improvement in the systematics and future survey projects, these indications will develop into a definitive measurement of neutrino masses.

scholarly journals Constraining the ΛCDM and Galileon models with recent cosmological data

2017 ◽  
Vol 600 ◽  
pp. A40 ◽  
Author(s):  
J. Neveu ◽  
V. Ruhlmann-Kleider ◽  
P. Astier ◽  
M. Besançon ◽  
J. Guy ◽  
...  
Keyword(s):  
Cosmological Parameters ◽  
Acoustic Oscillation ◽  
Gravity Models ◽  
Accelerated Expansion ◽  
Data Sets ◽  
Late Time ◽  
Lunar Laser Ranging ◽  
Cosmological Constraints ◽  
Cosmological Data ◽  
Speed Of Propagation

Aims. The Galileon theory belongs to the class of modified gravity models that can explain the late-time accelerated expansion of the Universe. In previous works, cosmological constraints on the Galileon model were derived, both in the uncoupled case and with a disformal coupling of the Galileon field to matter. There, we showed that these models agree with the most recent cosmological data. In this work, we used updated cosmological data sets to derive new constraints on Galileon models, including the case of a constant conformal Galileon coupling to matter. We also explored the tracker solution of the uncoupled Galileon model. Methods. After updating our data sets, especially with the latest Planck data and baryonic acoustic oscillation (BAO) measurements, we fitted the cosmological parameters of the ΛCDM and Galileon models. The same analysis framework as in our previous papers was used to derive cosmological constraints, using precise measurements of cosmological distances and of the cosmic structure growth rate. Results. We show that all tested Galileon models are as compatible with cosmological data as the ΛCDM model. This means that present cosmological data are not accurate enough to distinguish clearly between the two theories. Among the different Galileon models, we find that a conformal coupling is not favoured, contrary to the disformal coupling which is preferred at the 2.3σ level over the uncoupled case. The tracker solution of the uncoupled Galileon model is also highly disfavoured owing to large tensions with supernovae and Planck+BAO data. However, outside of the tracker solution, the general uncoupled Galileon model, as well as the general disformally coupled Galileon model, remain the most promising Galileon scenarios to confront with future cosmological data. Finally, we also discuss constraints coming from the Lunar Laser Ranging experiment and gravitational wave speed of propagation.

scholarly journals Determining the systemic redshift of Lyman α emitters with neural networks and improving the measured large-scale clustering

2020 ◽  
Vol 500 (1) ◽  
pp. 603-626
Author(s):  
Siddhartha Gurung-López ◽  
Shun Saito ◽  
Carlton M Baugh ◽  
Silvia Bonoli ◽  
Cedric G Lacey ◽  
...  
Keyword(s):  
Neural Networks ◽  
Line Profile ◽  
Large Scale ◽  
Line Profiles ◽  
Machine Learning Technique ◽  
Uniform Sampling ◽  
Novel Approach ◽  
Learning Technique ◽  
The Galaxy ◽  
Galaxy Sample

ABSTRACT We explore how to mitigate the clustering distortions in Lyman α emitter (LAE) samples caused by the misidentification of the Lyman α ($\rm {Ly}\,\alpha$) wavelength in their $\rm {Ly}\,\alpha$ line profiles. We use the $\rm {Ly}\,\alpha$ line profiles from our previous LAE theoretical model that includes radiative transfer in the interstellar and intergalactic mediums. We introduce a novel approach to measure the systemic redshift of LAEs from their $\rm {Ly}\,\alpha$ line using neural networks. In detail, we assume that for a fraction of the whole LAE population their systemic redshift is determined precisely through other spectral features. We then use this subset to train a neural network that predicts the $\rm {Ly}\,\alpha$ wavelength given an $\rm {Ly}\,\alpha$ line profile. We test two different training sets: (i) the LAEs are selected homogeneously and (ii) only the brightest LAE is selected. In comparison with previous approaches in the literature, our methodology improves significantly the accuracy in determining the $\rm {Ly}\,\alpha$ wavelength. In fact, after applying our algorithm in ideal $\rm {Ly}\,\alpha$ line profiles, we recover the clustering unperturbed down to $1\, {\rm cMpc}\, h^{-1}$. Then, we test the performance of our methodology in realistic $\rm {Ly}\,\alpha$ line profiles by downgrading their quality. The machine learning technique using the uniform sampling works well even if the $\rm {Ly}\,\alpha$ line profile quality is decreased considerably. We conclude that LAE surveys such as HETDEX would benefit from determining with high accuracy the systemic redshift of a subpopulation and applying our methodology to estimate the systemic redshift of the rest of the galaxy sample.

scholarly journals Beyond ΛCDM with H i intensity mapping: robustness of cosmological constraints in the presence of astrophysics

2020 ◽  
Vol 496 (4) ◽  
pp. 4115-4126 ◽  
Author(s):  
Stefano Camera ◽  
Hamsa Padmanabhan
Keyword(s):  
Dark Matter ◽  
Modified Gravity ◽  
Cosmological Parameters ◽  
Neutral Hydrogen ◽  
Temperature Fluctuations ◽  
Dark Matter Halo ◽  
Cosmological Constraints ◽  
Intensity Mapping ◽  
Standard Cosmological Model ◽  
First Time

ABSTRACT Mapping the unresolved intensity of the 21-cm emission of neutral hydrogen (H i) is now regarded as one the most promising tools for cosmological investigation in the coming decades. Here, we investigate, for the first time, extensions of the standard cosmological model, such as modified gravity and primordial non-Gaussianity, taking self-consistently into account. The present constraints on the astrophysics of H i clustering in the treatment of the brightness temperature fluctuations. To understand the boundaries within which results thus obtained can be considered reliable, we examine the robustness of cosmological parameter estimation performed via studies of 21-cm intensity mapping, against our knowledge of the astrophysical processes leading to H i clustering. Modelling of astrophysical effects affects cosmological observables through the relation linking the overall H i mass in a bound object, to the mass of the underlying dark matter halo that hosts it. We quantify the biases in estimates of standard cosmological parameters and those describing modified gravity and primordial non-Gaussianity that are obtained if one misconceives the slope of the relation between H i mass and halo mass, or the lower virial velocity cut-off for a dark matter halo to be able to host H i. Remarkably, we find that astrophysical uncertainties will not affect searches for primordial non-Gaussianity – one of the strongest science cases for H i intensity mapping – despite the signal being deeply linked to the H i bias.

scholarly journals KiDS + GAMA: constraints on horndeski gravity from combined large-scale structure probes

2019 ◽  
Vol 490 (2) ◽  
pp. 2155-2177 ◽  
Author(s):  
A Spurio Mancini ◽  
F Köhlinger ◽  
B Joachimi ◽  
V Pettorino ◽  
B M Schäfer ◽  
...  
Keyword(s):  
Dark Energy ◽  
Large Scale ◽  
Gravity Models ◽  
Dark Energy Density ◽  
Modelling Uncertainty ◽  
Matter Power Spectrum ◽  
Downward Shift ◽  
The Galaxy ◽  
Best Fitting ◽  
Mass Assembly

ABSTRACT We present constraints on Horndeski gravity from a combined analysis of cosmic shear, galaxy–galaxy lensing and galaxy clustering from $450\, \mathrm{deg}^2$ of the Kilo-Degree Survey and the Galaxy And Mass Assembly survey.The Horndeski class of dark energy/modified gravity models includes the majority of universally coupled extensions to ΛCDM with one scalar field in addition to the metric. We study the functions of time that fully describe the evolution of linear perturbations in Horndeski gravity. Our results are compatible throughout with a ΛCDM model. By imposing gravitational wave constraints, we fix the tensor speed excess to zero and consider a subset of models including, e.g. quintessence and f(R) theories. Assuming proportionality of the Horndeski functions αB and αM (kinetic braiding and the Planck mass run rate, respectively) to the dark energy density fraction ΩDE(a) = 1 − Ωm(a), we find for the proportionality coefficients $\hat{\alpha }_\mathrm{ B} = 0.20_{-0.33}^{+0.20} \,$ and $\, \hat{\alpha }_\mathrm{ M} = 0.25_{-0.29}^{+0.19}$. Our value of $S_8 \equiv \sigma _8 \sqrt{\Omega _{\mathrm{m}}/0.3}$ is in better agreement with the Planck estimate when measured in the enlarged Horndeski parameter space than in a pure ΛCDM scenario. In our joint three-probe analysis, we report a downward shift of the S8 best-fitting value from the Planck measurement of $\Delta S_8 = 0.016_{-0.046}^{+0.048}$ in Horndeski gravity, compared to $\Delta S_8 = 0.059_{-0.039}^{+0.040}$ in ΛCDM. Our constraints are robust to the modelling uncertainty of the non-linear matter power spectrum in Horndeski gravity. Our likelihood code for multiprobe analysis in both ΛCDM and Horndeski gravity is publicly available at https://github.com/alessiospuriomancini/KiDSHorndeski.

scholarly journals New perspectives on the BOSS small-scale lensing discrepancy for the Planck ΛCDM cosmology

2019 ◽  
Vol 488 (4) ◽  
pp. 5771-5787 ◽  
Author(s):  
Johannes U Lange ◽  
Xiaohu Yang ◽  
Hong Guo ◽  
Wentao Luo ◽  
Frank C van den Bosch
Keyword(s):  
Cosmological Parameters ◽  
Sloan Digital Sky Survey ◽  
Small Scale ◽  
Microwave Background ◽  
Sky Survey ◽  
The Galaxy ◽  
Galaxy Sample ◽  
Moderate Change ◽  
Stellar Masses ◽  
Expected Signal

ABSTRACT We investigate the abundance, small-scale clustering, and galaxy–galaxy lensing signal of galaxies in the Baryon Oscillation Spectroscopic Survey (BOSS). To this end, we present new measurements of the redshift and stellar mass dependence of the lensing properties of the galaxy sample. We analyse to what extent models assuming the Planck18 cosmology fit to the number density and clustering can accurately predict the small-scale lensing signal. In qualitative agreement with previous BOSS studies at redshift z ∼ 0.5 and with results from the Sloan Digital Sky Survey, we find that the expected signal at small scales ($0.1 \lt r_{\rm p}\lt 3 \, h^{-1}\, {\rm {Mpc}}$) is higher by $\sim 25{{\ \rm per\ cent}}$ than what is measured. Here, we show that this result is persistent over the redshift range 0.1 < z < 0.7 and for galaxies of different stellar masses. If interpreted as evidence for cosmological parameters different from the Planck cosmic microwave background (CMB) findings, our results imply $S_8 = \sigma _8 \sqrt{\Omega _{\rm m}/ 0.3} = 0.744 \pm 0.015$, whereas S8 = 0.832 ± 0.013 for Planck18. However, in addition to being in tension with CMB results, such a change in cosmology alone does not accurately predict the lensing amplitude at larger scales. Instead, other often neglected systematics like baryonic feedback or assembly bias are likely contributing to the small-scale lensing discrepancy. We show that either effect alone, though, is unlikely to completely resolve the tension. Ultimately, a combination of the two effects in combination with a moderate change in cosmological parameters might be needed.

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.

scholarly journals Cosmological Constraints on Mirror Matter Parameters

2014 ◽  
Vol 2014 ◽  
pp. 1-7
Author(s):  
Paolo Ciarcelluti ◽  
Quentin Wallemacq
Keyword(s):  
Monte Carlo ◽  
Dark Matter ◽  
Large Scale ◽  
Cold Dark Matter ◽  
Cosmological Parameters ◽  
Linear Regime ◽  
Microwave Background ◽  
Cosmological Constraints ◽  
Upper Limits ◽  
Mirror Matter

Up-to-date estimates of the cosmological parameters are presented as a result of numerical simulations of cosmic microwave background and large scale structure, considering a flat Universe in which the dark matter is made entirely or partly of mirror matter, and the primordial perturbations are scalar adiabatic and in linear regime. A statistical analysis using the Markov Chain Monte Carlo method allows to obtain constraints of the cosmological parameters. As a result, we show that a Universe with pure mirror dark matter is statistically equivalent to the case of an admixture with cold dark matter. The upper limits for the ratio of the temperatures of ordinary and mirror sectors are around 0.3 for both the cosmological models, which show the presence of a dominant fraction of mirror matter,0.06≲Ωmirrorh2≲0.12.

scholarly journals Bounce cosmology in $$f({\mathcal {R}})$$ gravity

2021 ◽  
Vol 81 (2) ◽  
Author(s):  
M. Ilyas ◽  
W. U. Rahman
Keyword(s):  
Cosmological Parameters ◽  
Cosmic Time ◽  
Big Bang ◽  
Gravity Theory ◽  
Gravity Models ◽  
Late Time ◽  
Time Stability ◽  
Shift Parameter ◽  
Cosmological Constraints ◽  
Bouncing Cosmology

AbstractIn this paper, we analyze the modified $$f({\mathcal {R}})$$ f ( R ) gravity models in Friedmann–Lemaître–Robertson–Walker (FLRW) background. The actions of bouncing cosmology are studied under consideration of different viable models in $$f({\mathcal {R}})$$ f ( R ) gravity theory that can resolve the difficulty of singularity in standard Big-Bang cosmology. Under different viable models in $$f({\mathcal {R}})$$ f ( R ) gravity theory, the cosmological constraints are plotted in provisions of cosmic-time, then investigated the bounce circumstance. In addition, the red-shift parameter is used to reconstruct the modified gravity, and compile the cosmological parameters that infer accelerated universe expansion. Finally, the situation stability is evaluated with a sound speed feature, which illustrates late-time stability.

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