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Register a new userBaryon acoustic oscillations signature in the three-point angular correlation function from the SDSS-DR12 quasar survey
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Edilson de Carvalho Filho
Publication date
2020
fields
Physics
and research's language is
English
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The clustering properties of the Universe at large-scales are currently being probed at various redshifts through several cosmological tracers and with diverse statistical estimators. Here we use the three-point angular correlation function (3PACF) to probe the baryon acoustic oscillation (BAO) features in the quasars catalogue from the twelfth data release of the Sloan Digital Sky Survey, with mean redshift z = 2.225, detecting the BAO imprint with a statistical significance of 2.9{sigma}, obtained using lognormal mocks. Following a quasi model-independent approach for the 3PACF, we find the BAO transversal signature for triangles with sides $theta_1 = 1.0^circ$ and $theta_2 = 1.5^circ$ and the angle between them of $alpha = 1.59 pm 0.17$ rad, a value that corresponds to the angular BAO scale ${theta}_{BAO} = 1.82^circ pm 0.21^circ$ , in excellent agreement with the value found in a recent work (${theta}_{BAO} = 1.77^circ pm 0.31^circ$ ) applying the 2PACF to similar data. Moreover, we performed two type of tests: one to confirm the robustness of the BAO signal in the 3PACF through random displacements in the dataset, and the other to verify the suitability of our random samples, a null test that in fact does not show any signature that could bias our results.
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The 2-point angular correlation function $w(theta)$ (2PACF), where $theta$ is the angular separation between pairs of galaxies, provides the transversal Baryon Acoustic Oscillation (BAO) signal almost model-independently. In this paper we use 409,337 luminous red galaxies in the redshift range $z = [0.440,0.555]$ obtained from the tenth data release of the Sloan Digital Sky Survey (SDSS DR10) to estimate $theta_{rm{BAO}}(z)$ from the 2PACF at six redshift {shells}. Since noise and systematics can hide the BAO signature in the $w - theta$ plane, we also discuss some criteria to localize the acoustic bump. We identify two sources of model-dependence in the analysis, namely, the value of the acoustic scale from Cosmic Microwave Background (CMB) measurements and the correction in the $theta_{rm{BAO}}(z)$ position due to projection effects. Constraints on the dark energy equation-of-state parameter w$(z)$ from the $theta_{rm{BAO}}(z)$ diagram are derived, as well as from a joint analysis with current CMB measurements. We find that the standard $Lambda$CDM model as well as some of its extensions are in good agreement with these $theta_{rm{BAO}}(z)$ measurements.
We present a measurement of baryon acoustic oscillations (BAO) in the cross-correlation of quasars with the Ly$alpha$-forest flux-transmission at a mean redshift $z=2.40$. The measurement uses the complete SDSS-III data sample: 168,889 forests and 234,367 quasars from the SDSS Data Release DR12. In addition to the statistical improvement on our previous study using DR11, we have implemented numerous improvements at the analysis level allowing a more accurate measurement of this cross-correlation. We also developed the first simulations of the cross-correlation allowing us to test different aspects of our data analysis and to search for potential systematic errors in the determination of the BAO peak position. We measure the two ratios $D_{H}(z=2.40)/r_{d} = 9.01 pm 0.36$ and $D_{M}(z=2.40)/r_{d} = 35.7 pm 1.7$, where the errors include marginalization over the non-linear velocity of quasars and the metal - quasar cross-correlation contribution, among other effects. These results are within $1.8sigma$ of the prediction of the flat-$Lambda$CDM model describing the observed CMB anisotropies. We combine this study with the Ly$alpha$-forest auto-correlation function [2017A&A...603A..12B], yielding $D_{H}(z=2.40)/r_{d} = 8.94 pm 0.22$ and $D_{M}(z=2.40)/r_{d} = 36.6 pm 1.2$, within $2.3sigma$ of the same flat-$Lambda$CDM model.
Following a quasi model-independent approach we measure the transversal BAO mode at high redshift using the two-point angular correlation function (2PACF). The analyses done here are only possible now with the quasar catalogue from the twelfth data release (DR12Q) from the Sloan Digital Sky Survey, because it is spatially dense enough to allow the measurement of the angular BAO signature with moderate statistical significance and acceptable precision. Our analyses with quasars in the redshift interval z = [2.20,2.25] produce the angular BAO scale theta_BAO = 1.77 +- 0.31 deg with a statistical significance of 2.12 sigma (i.e., 97% confidence level), calculated through a likelihood analysis performed using the theoretical covariance matrix sourced by the analytical power spectra expected in the LCDM concordance model. Additionally, we show that the BAO signal is robust -although with less statistical significance- under diverse bin-size choices and under small displacements of the quasars angular coordinates. Finally, we also performed cosmological parameter analyses comparing the theta_BAO predictions for wCDM and w(a)CDM models with angular BAO data available in the literature, including the measurement obtained here, jointly with CMB data. The constraints on the parameters Omega_M, w_0 and w_a are in excellent agreement with the LCDM concordance model.
We present baryon acoustic oscillation (BAO) scale measurements determined from the clustering of 1.2 million massive galaxies with redshifts 0.2 < z < 0.75 distributed over 9300 square degrees, as quantified by their redshift-space correlation function. In order to facilitate these measurements, we define, describe, and motivate the selection function for galaxies in the final data release (DR12) of the SDSS III Baryon Oscillation Spectroscopic Survey (BOSS). This includes the observational footprint, masks for image quality and Galactic extinction, and weights to account for density relationships intrinsic to the imaging and spectroscopic portions of the survey. We simulate the observed systematic trends in mock galaxy samples and demonstrate that they impart no bias on baryon acoustic oscillation (BAO) scale measurements and have a minor impact on the recovered statistical uncertainty. We measure transverse and radial BAO distance measurements in 0.2 < z < 0.5, 0.5 < z < 0.75, and (overlapping) 0.4 < z < 0.6 redshift bins. In each redshift bin, we obtain a precision that is 2.7 per cent or better on the radial distance and 1.6 per cent or better on the transverse distance. The combination of the redshift bins represents 1.8 per cent precision on the radial distance and 1.1 per cent precision on the transverse distance. This paper is part of a set that analyses the final galaxy clustering dataset from BOSS. The measurements and likelihoods presented here are combined with others in Alam et al. (2016) to produce the final cosmological constraints from BOSS.
We present a new determination of the large-scale clustering of the CIV forest (i.e., the absorption due to all CIV absorbers) using its cross-correlation with quasars in the Sloan Digital Sky Survey (SDSS) Data Release 12 (DR12). We fit a linear bias model to the measured cross-correlation. We find that the transmission bias of the CIV forest, $b_{Fc}$, at a mean redshift of $z=2.3$, obeys the relation $(1+beta_c)b_{F c} = -0.024 pm 0.003$. Here, $beta_{c}$ is the linear redshift space distortion parameter of the CIV absorption, which can only be poorly determined at $beta_c=1.1pm 0.6$ from our data. This transmission bias is related to the bias of CIV absorbers and their host halos through the effective mean optical depth of the CIV forest, $bartau_c$. Estimating a value $bar tau_c(z) simeq 0.01$ from previous studies of the CIV equivalent width distribution, our measurement implies a CIV absorber bias near unity, with a large error due to uncertainties in both $beta_c$ and $bartau_c$. This makes it compatible with the higher DLA bias $b_{rm DLA}simeq 2$ measured previously from the cross-correlation of DLAs and the Lyman-$alpha$ forest. We discuss the implications of the CIV absorber bias for the mass distribution of their host halos. More accurate determinations of $bar tau_c(z)$ and $beta_c$ are necessary to obtain a more robust measurement of this CIV absorber bias.
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