A&A 603, A12 (2017) We use flux-transmission correlations in \Lya forests to measure the imprint
of baryon acoustic oscillations (BAO). The study uses spectra of 157,783
quasars in the redshift range ...$2.1\le z \le 3.5$ from the Sloan Digital Sky
Survey (SDSS) Data Release 12 (DR12). Besides the statistical improvements on
our previous studies using SDSS DR9 and DR11, we have implemented numerous
improvements in the analysis procedure, allowing us to construct a physical
model of the correlation function and to investigate potential systematic
errors in the determination of the BAO peak position. The Hubble distance,
$\DHub=c/H(z)$, relative to the sound horizon is $\DHub(z=2.33)/r_d=9.07 \pm
0.31$. The best-determined combination of comoving angular-diameter distance,
$\DM$, and the Hubble distance is found to be
$\DHub^{0.7}\DM^{0.3}/r_d=13.94\pm0.35$. This value is $1.028\pm0.026$ times
the prediction of the flat-\lcdm model consistent with the cosmic microwave
background (CMB) anisotropy spectrum. The errors include marginalization over
the effects of unidentified high-density absorption systems and fluctuations in
ultraviolet ionizing radiation. Independently of the CMB measurements, the
combination of our results and other BAO observations determine the open-\lcdm
density parameters to be $\om=0.296 \pm 0.029$, $\ol=0.699 \pm 0.100$ and
$\Omega_k = -0.002 \pm 0.119$.
(Abridged) We detect the large-scale structure of Lya emission in the Universe at redshifts z=2-3.5 by measuring the cross-correlation of Lya surface brightness with quasars in SDSS/BOSS. We use a ...million spectra targeting Luminous Red Galaxies at z<0.8, after subtracting a best fit model galaxy spectrum from each one, as an estimate of the high-redshift Lya surface brightness. The quasar-Lya emission cross-correlation we detect has a shape consistent with a LambdaCDM model with Omega_M =0.30^+0.10-0.07. The predicted amplitude of this cross-correlation is proportional to the product of the mean Lya surface brightness, , the amplitude of mass fluctuations, and the quasar and Lya emission bias factors. Using known values, we infer (b_alpha/3) = (3.9 +/- 0.9) x 10^-21 erg/s cm^-2 A^-1 arcsec^-2, where b_alpha is the Lya emission bias factor. If the dominant sources of Lya emission are star forming galaxies, we infer rho_SFR = (0.28 +/- 0.07) (3/b_alpha) /yr/Mpc^3 at z=2-3.5. For b_alpha=3, this value is a factor of 21-35 above previous estimates from individually detected Lya emitters, although consistent with the total rho_SFR derived from dust-corrected, continuum UV surveys. 97% of the Lya emission in the Universe at these redshifts is therefore undetected in previous surveys of Lya emitters. Our measurement is much greater than seen from stacking analyses of faint halos surrounding previously detected Lya emitters, but we speculate that it arises from similar Lya halos surrounding all luminous star-forming galaxies. We also detect redshift space anisotropy of the quasar-Lya emission cross-correlation, finding evidence at the 3.0 sigma level that it is radially elongated, consistent with distortions caused by radiative-transfer effects (Zheng et al. (2011)). Our measurements represent the first application of the intensity mapping technique to optical observations.
We report a detection of the baryon acoustic oscillation (BAO) feature in the flux-correlation function of the Ly{\alpha} forest of high-redshift quasars with a statistical significance of five ...standard deviations. The study uses 137,562 quasars in the redshift range \(2.1\le z \le 3.5\) from the Data Release 11 (DR11) of the Baryon Oscillation Spectroscopic Survey (BOSS) of SDSS-III. This sample contains three times the number of quasars used in previous studies. The measured position of the BAO peak determines the angular distance, \(D_A(z=2.34)\) and expansion rate, \(H(z=2.34)\), both on a scale set by the sound horizon at the drag epoch, \(r_d\). We find \(D_A/r_d=11.28\pm0.65(1\sigma)^{+2.8}_{-1.2}(2\sigma)\) and \(D_H/r_d=9.18\pm0.28(1\sigma)\pm0.6(2\sigma)\) where \(D_H=c/H\). The optimal combination, \(\sim D_H^{0.7}D_A^{0.3}/r_d\) is determined with a precision of \(\sim2\%\). For the value \(r_d=147.4~{\rm Mpc}\), consistent with the CMB power spectrum measured by Planck, we find \(D_A(z=2.34)=1662\pm96(1\sigma)~{\rm Mpc}\) and \(H(z=2.34)=222\pm7(1\sigma)~{\rm km\,s^{-1}Mpc^{-1}}\). Tests with mock catalogs and variations of our analysis procedure have revealed no systematic uncertainties comparable to our statistical errors. Our results agree with the previously reported BAO measurement at the same redshift using the quasar-Ly{\alpha} forest cross-correlation. The auto-correlation and cross-correlation approaches are complementary because of the quite different impact of redshift-space distortion on the two measurements. The combined constraints from the two correlation functions imply values of \(D_A/r_d\) and \(D_H/r_d\) that are, respectively, 7% low and 7% high compared to the predictions of a flat \(\Lambda\)CDM cosmological model with the best-fit Planck parameters. With our estimated statistical errors, the significance of this discrepancy is \(\approx 2.5\sigma\).
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 \(1.8\sigma\) 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 \(2.3\sigma\) of the same flat-\(\Lambda\)CDM model.
We describe fitting methods developed to analyze fluctuations in the Lyman-{\alpha} forest and measure the parameters of baryon acoustic oscillations (BAO). We apply our methods to BOSS Data Release ...9. Our method is based on models of the three-dimensional correlation function in physical coordinate space, and includes the effects of redshift-space distortions, anisotropic non-linear broadening, and broadband distortions. We allow for independent scale factors along and perpendicular to the line of sight to minimize the dependence on our assumed fiducial cosmology and to obtain separate measurements of the BAO angular and relative velocity scales. Our fitting software and the input files needed to reproduce our main BOSS Data Release 9 results are publicly available.
We have developed two independent methods to measure the one-dimensional power spectrum of the transmitted flux in the Lyman-\(\alpha\) forest. The first method is based on a Fourier transform, and ...the second on a maximum likelihood estimator. The two methods are independent and have different systematic uncertainties. The determination of the noise level in the data spectra was subject to a novel treatment, because of its significant impact on the derived power spectrum. We applied the two methods to 13,821 quasar spectra from SDSS-III/BOSS DR9 selected from a larger sample of over 60,000 spectra on the basis of their high quality, large signal-to-noise ratio, and good spectral resolution. The power spectra measured using either approach are in good agreement over all twelve redshift bins from \( = 2.2\) to \( = 4.4\), and scales from 0.001 \(\rm(km/s)^{-1}\) to \(0.02 \rm(km/s)^{-1}\). We determine the methodological and instrumental systematic uncertainties of our measurements. We provide a preliminary cosmological interpretation of our measurements using available hydrodynamical simulations. The improvement in precision over previously published results from SDSS is a factor 2--3 for constraints on relevant cosmological parameters. For a \(\Lambda\)CDM model and using a constraint on \(H_0\) that encompasses measurements based on the local distance ladder and on CMB anisotropies, we infer \(\sigma_8 =0.83\pm0.03\) and \(n_s= 0.97\pm0.02\) based on \ion{H}{i} absorption in the range \(2.1<z<3.7\).
We measure the large-scale cross-correlation of quasars with the Lyman alpha
forest absorption, using over 164,000 quasars from Data Release 11 of the
SDSS-III Baryon Oscillation Spectroscopic ...Survey. We extend the previous study
of roughly 60,000 quasars from Data Release 9 to larger separations, allowing a
measurement of the Baryonic Acoustic Oscillation (BAO) scale along the line of
sight $c/(H(z=2.36) ~ r_s) = 9.0 \pm 0.3$ and across the line of sight
$D_A(z=2.36) / ~ r_s = 10.8 \pm 0.4$, consistent with CMB and other BAO data.
Using the best fit value of the sound horizon from Planck data ($r_s=147.49
Mpc$), we can translate these results to a measurement of the Hubble parameter
of $H(z=2.36) = 226 \pm 8 km/s / Mpc$ and of the angular diameter distance of
$D_A(z=2.36) = 1590 \pm 60 Mpc$. The measured cross-correlation function and an
update of the code to fit the BAO scale (baofit) are made publicly available.
We use flux-transmission correlations in \Lya forests to measure the imprint of baryon acoustic oscillations (BAO). The study uses spectra of 157,783 quasars in the redshift range \(2.1\le z \le ...3.5\) from the Sloan Digital Sky Survey (SDSS) Data Release 12 (DR12). Besides the statistical improvements on our previous studies using SDSS DR9 and DR11, we have implemented numerous improvements in the analysis procedure, allowing us to construct a physical model of the correlation function and to investigate potential systematic errors in the determination of the BAO peak position. The Hubble distance, \(\DHub=c/H(z)\), relative to the sound horizon is \(\DHub(z=2.33)/r_d=9.07 \pm 0.31\). The best-determined combination of comoving angular-diameter distance, \(\DM\), and the Hubble distance is found to be \(\DHub^{0.7}\DM^{0.3}/r_d=13.94\pm0.35\). This value is \(1.028\pm0.026\) times the prediction of the flat-\lcdm model consistent with the cosmic microwave background (CMB) anisotropy spectrum. The errors include marginalization over the effects of unidentified high-density absorption systems and fluctuations in ultraviolet ionizing radiation. Independently of the CMB measurements, the combination of our results and other BAO observations determine the open-\lcdm density parameters to be \(\om=0.296 \pm 0.029\), \(\ol=0.699 \pm 0.100\) and \(\Omega_k = -0.002 \pm 0.119\).
We present the Data Release 10 Quasar (DR10Q) catalog from the Baryon Oscillation Spectroscopic Survey (BOSS) of the Sloan Digital Sky Survey III. The catalog includes all BOSS objects that were ...targeted as quasar candidates during the first 2.5 years of the survey and that are confirmed as quasars via visual inspection of the spectra. The catalog also includes known quasars (mostly from SDSS-I and II) that were reobserved by BOSS. The catalog contains 166,583 quasars (74,454 are new discoveries since SDSS-DR9) detected over 6,373 deg\(^{2}\) with robust identification and redshift measured by a combination of principal component eigenspectra. The number of quasars with \(z>2.15\) (117,668) is \(\sim\)5 times greater than the number of \(z>2.15\) quasars known prior to BOSS. Redshifts and FWHMs are provided for the strongest emission lines (CIV, CIII, MgII). The catalog identifies 16,461 broad absorption line quasars and gives their characteristics. For each object, the catalog presents five-band (u, g, r, i, z) CCD-based photometry with typical accuracy of 0.03 mag and information on the optical morphology and selection method. The catalog also contains X-ray, ultraviolet, near-infrared, and radio emission properties of the quasars, when available, from other large-area surveys. The calibrated digital spectra cover the wavelength region 3,600-10,500\AA\ at a spectral resolution in the range 1,300\(<\)R\(<\)2,500; the spectra can be retrieved from the SDSS Catalog Archive Server. We also provide a supplemental list of an additional 2,376 quasars that have been identified among the galaxy targets of the SDSS-III/BOSS.
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