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Register a new userRedshift-weighted constraints on primordial non-Gaussianity from the clustering of the eBOSS DR14 quasars in Fourier space
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We present constraints on local primordial non-Gaussianity (PNG), parametrized through $f^{rm loc}_{rm NL}$, using the Sloan Digital Sky Survey IV extended Baryon Oscillation Spectroscopic Survey Data Release 14 quasar sample. We measure and analyze the anisotropic clustering of the quasars in Fourier space, testing for the scale-dependent bias introduced by primordial non-Gaussianity on large scales. We derive and employ a power spectrum estimator using optimal weights that account for the redshift evolution of the PNG signal. We find constraints of $-51<f^{rm loc}_{rm NL}<21$ at 95% confidence level. These are amont the tightest constraints from Large Scale Structure (LSS) data. Our redshift weighting improves the error bar by 15% in comparison to the unweighted case. If quasars have lower response to PNG, the constraint degrades to $-81<f^{rm loc}_{rm NL}<26$, with a 40% improvement over the standard approach. We forecast that the full eBOSS dataset could reach $sigma_{f^{rm loc}_{rm NL}}simeq 5text{-}8$ using optimal methods and full range of scales.
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We derive robust constraints on primordial non-Gaussianity (PNG) using the clustering of 800,000 photometric quasars from the Sloan Digital Sky Survey in the redshift range $0.5<z<3.5$. These measurements rely on the novel technique of {it extended mode projection} to control the impact of spatially-varying systematics in a robust fashion, making use of blind analysis techniques. This allows the accurate measurement of quasar halo bias at the largest scales, while discarding as little as possible of the data. The standard local-type PNG parameters $f_mathrm{NL}$ and $g_mathrm{NL}$ both imprint a $k^{-2}$ scale-dependent effect in the bias. Constraining these individually, we obtain $-49<f_mathrm{NL}<31$ and $-2.7times10^5<g_mathrm{NL}<1.9times10^5$, while their joint constraints lead to $-105<f_mathrm{NL}<72$ and $-4.0times10^5<g_mathrm{NL}<4.9times10^5$ (all at 95% CL) . Introducing a running parameter $n_{f_mathrm{NL}}$ to constrain $b(k) propto k^{-2+n_{f_mathrm{NL}}}$ and a generalised PNG amplitude $tilde{f}_mathrm{NL}$, we obtain $-45.5 exp({3.7, n_{f_mathrm{NL}}}) < tilde{f}_mathrm{NL} < 34.4 exp({3.3, n_{f_mathrm{NL}}})$ at 95% CL. These results incorporate uncertainties in the cosmological parameters, redshift distributions, shot noise, and the bias prescription used to relate the quasar clustering to the underlying dark matter. These are the strongest constraints obtained to date on PNG using a single population of large-scale structure tracers, and are already at the level of pre-{it Planck} constraints from the cosmic microwave background. A conservative forecast for a {it Large Synoptic Survey Telescope}-like survey incorporating mode projection yields $sigma(f_mathrm{NL}) sim 5$ -- competitive with the {it Planck} result -- highlighting the power of upcoming large scale structure surveys to probe the initial conditions of the universe.
We present measurements of the local primordial non-Gaussianity parameter fNLloc from the clustering of 343,708 quasars with redshifts 0.8 < z < 2.2 distributed over 4808 square degrees from the final data release (DR16) of the extended Baryon acoustic Oscillation Spectroscopic Survey (eBOSS), the largest volume spectroscopic survey up to date. Our analysis is performed in Fourier space, using the power spectrum monopole at very large scales to constrain the scale dependent halo bias. We carefully assess the impact of systematics on our measurement and test multiple contamination removal methods. We demonstrate the robustness of our analysis pipeline with EZ-mock catalogues that simulate the eBOSS DR16 target selection. We find $f_mathrm{NL}=-12pm 21$ (68% confidence) for the main clustering sample including quasars with redshifts between 0.8 and 2.2, after exploiting a novel neural network scheme for cleaning the DR16 sample and in particular after applying redshift weighting techniques, designed for non-Gaussianity measurement from large scales structure, to optimize our analysis, which improve our results by 37%.
The anisotropy of the redshift space bispectrum contains a wealth of cosmological information. This anisotropy depends on the orientation of three vectors ${bf k_1,k_2,k_3}$ with respect to the line of sight. Here we have decomposed the redshift space bispectrum in spherical harmonics which completely quantify this anisotropy. To illustrate this we consider linear redshift space distortion of the bispectrum arising from primordial non-Gaussianity. In the plane parallel approximation only the first four even $ell$ multipoles have non-zero values, and we present explicit analytical expressions for all the non-zero multipoles {it i.e.} upto $ell=6,m=4$. The ratio of the different multipole moments to the real space bispectrum depends only on $beta_1$ the linear redshift distortion parameter and the shape of the triangle. Considering triangles of all possible shapes, we have studied how this ratio depends on the shape of the triangle for $beta_1=1$. We have also studied the $beta_1$ dependence for some of the extreme triangle shapes. If measured in future, these multipole moments hold the potential of constraining $beta_1$. The results presented here are also important if one wishes to constrain $f_{text{NL}}$ using redshift surveys.
We present catalogues of cosmic voids identified in the distribution of Luminous Red Galaxies (LRGs) and Quasi Stellar Objects (QSOs) in the fourteenth data release (DR14) of the extended Baryon Oscillation Spectroscopic Survey (eBOSS). We perform a multivariate analysis to assess the level of contamination in these catalogues by spurious Poisson underdensities. We find that the LRG void catalogue is largely free from contamination but that the QSO catalogue may be heavily contaminated. We analyse the multipoles of the void-galaxy cross-correlation function in these catalogues to obtain constraints on the growth rate of structure around voids. We find a value of $beta(z=0.703)=0.58^{+0.33}_{-0.28}$ for the LRG voids and $beta(z=1.53)=0.15^{+0.13}_{-0.12}$ for the QSO voids.
We use Minkowski Functionals (MF) to constrain a primordial non-Gaussian contribution to the CMB intensity field as observed in the 150 GHz and 145 GHz BOOMERanG maps from the 1998 and 2003 flights, respectively, performing for the first time a joint analysis of the two datasets. A perturbative expansion of the MF formulae in the limit of a weakly non-Gaussian field yields analytical formulae, derived by Hikage et al. (2006), which can be used to constrain the coupling parameter f_NL without the need for non-Gaussian simulations. We find -1020<f_NL<390 at 95% CL, significantly improving the previous constraints by De Troia et al. (2007) on the BOOMERanG 2003 dataset. These are the best f_NL limits to date for suborbital probes.
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