We measure the large-scale cross-correlation of quasars with the Lyα 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)rs) = 9.0±0.3 and across the line of sight DA (z = 2.36)/rs = 10.8±0.4, consistent with CMB and other BAO data. Using the best fit value of the sound horizon from Planck data (rs = 147.49 Mpc), we can translate these results to a measurement of the Hubble parameter of H(z = 2.36) = 226±8 km s -1 Mpc-1 and of the angular diameter distance of D A (z = 2.36) = 1590±60 Mpc. The measured cross-correlation function and an update of the code to fit the BAO scale (baofit) are made publicly available.©2014 IOP Publishing Ltd and Sissa Medialab srl.

We have developed two independent methods for measuring the one-dimensional power spectrum of the transmitted flux in the Lyman-α 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. Determination of the noise level in the data spectra was subject to a new 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, high signal-to-noise ratio (S/N), and good spectral resolution. The power spectra measured using either approach are in good agreement over all twelve redshift bins from 〈z〉 = 2.2 to 〈z〉 = 4.4, and scales from 0.001 km s -1 to 0.02 km s -1 . We determined the methodological andinstrumental 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 ΛCDM model and using a constraint on H 0 that encompasses measurements based on the local distance ladder and on CMB anisotropies, we infer σ 8 = 0.83 ± 0.03 and n s = 0.97 ± 0.02 based on Hi absorption in the range 2.1 < z < 3.7. © ESO, 2013.

We present the second edition of the Sloan Digital Sky Survey (SDSS) Quasar Catalog. The catalog consists of the 16,713 objects in the SDSS First Data Release that have luminosities larger than M i = -22 (in a cosmology with H 0 = 70 km s -1 Mpc -1 , Ω M = 0.3, and Ω ∇ = 0.7), have at least one emission line with FWHM larger than 1000 km s -1 , and have highly reliable redshifts. The area covered by the catalog is ≈ 1360 deg 2 . The quasar redshifts range from 0.08 to 5.41, with a median value of 1.43. For each object, the catalog presents positions accurate to better than 0.′2 rms per coordinate, five-band (ugriz) CCD-based photometry with typical accuracy of 0.03 mag, and information on the morphology and selection method. The catalog also contains some radio, near-infrared, and X-ray emission properties of the quasars, when available, from other large-area surveys. Calibrated digital spectra of all objects in the catalog, covering the wavelength region 3800-9200 Å at a spectral resolution of 1800-2100, are available. This publication supersedes the first SDSS Quasar Catalog, which was based on material from the SDSS Early Data Release. A summary of corrections to current quasar databases is also provided. The majority of the objects were found in SDSS commissioning data using a multicolor selection technique. Since the quasar selection algorithm was undergoing testing during the entire observational period covered by this catalog, care must be taken when assembling samples from the catalog for use in statistical studies. A total of 15,786 objects (94%) in the catalog were discovered by the SDSS; 12,173 of the SDSS discoveries are reported here for the first time. Included in the new discoveries are five quasars brighter than i= 16.0 and 17 quasars with redshifts larger than 4.5.

(Abridged) We describe here the most ambitious survey currently planned in the optical, the Large Synoptic Survey Telescope (LSST). A vast array of science will be enabled by a single wide-deep-fast sky survey, and LSST will have unique survey capability in the faint time domain. The LSST design is driven by four main science themes: probing dark energy and dark matter, taking an inventory of the Solar System, exploring the transient optical sky, and mapping the Milky Way. LSST will be a wide-field ground-based system sited at Cerro Pach {o}n in northern Chile. The telescope will have an 8.4 m (6.5 m effective) primary mirror, a 9.6 deg$^2$ field of view, and a 3.2 Gigapixel camera. The standard observing sequence will consist of pairs of 15-second exposures in a given field, with two such visits in each pointing in a given night. With these repeats, the LSST system is capable of imaging about 10,000 square degrees of sky in a single filter in three nights. The typical 5$\sigma$ point-source depth in a single visit in $r$ will be $\sim 24.5$ (AB). The project is in the construction phase and will begin regular survey operations by 2022. The survey area will be contained within 30,000 deg$^2$ with $\delta<+34.5^\circ$, and will be imaged multiple times in six bands, $ugrizy$, covering the wavelength range 320--1050 nm. About 90\% of the observing time will be devoted to a deep-wide-fast survey mode which will uniformly observe a 18,000 deg$^2$ region about 800 times (summed over all six bands) during the anticipated 10 years of operations, and yield a coadded map to $r\sim27.5$. The remaining 10\% of the observing time will be allocated to projects such as a Very Deep and Fast time domain survey. The goal is to make LSST data products, including a relational database of about 32 trillion observations of 40 billion objects, available to the public and scientists around the world.