The spectra of emission-line galaxies from the extended Baryon Oscillation Spectroscopic Survey of the Sloan Digit Sky Survey (SDSS) are used to study the mass?metallicity relation (MZR) at z;?;0.8. The selected sample contains about 180,000 massive star-forming galaxies with 0.6;z;<;1.05 and <CDATA<i. The spectra are stacked in bins of different parameters including redshift, stellar mass, star formation rate (SFR), specific star formation rate (sSFR), half-light radius, mass density, and optical color. The average MZR at z;?;0.83 has a downward evolution in the MZR from the local to high-redshift universe, which is consistent with previous works. At a specified stellar mass, galaxies with higher SFR/sSFR and larger half-light radius have systematically lower metallicity. This behavior is reversed for galaxies with larger mass density and optical color. Among the above physical parameters, the MZR has the most significant dependency on SFR. Our galaxy sample at 0.6;z;<;1.05 approximately follows the fundamental metallicity relation (FMR) in the local universe, although the sample inhomogeneity and incompleteness might have an effect on our MZR and FMR.

The DESI Legacy Imaging Surveys are a combination of three public projects (the Dark Energy Camera Legacy Survey, the Beijing-Arizona Sky Survey, and the Mayall z-band Legacy Survey) that will jointly image approximately 14,000 deg^2 of the extragalactic sky visible from the northern hemisphere in three optical bands (g, r, and z) using telescopes at the Kitt Peak National Observatory and the Cerro Tololo Inter-American Observatory. The combined survey footprint is split into two contiguous areas by the Galactic plane. The optical imaging is conducted using a unique strategy of dynamically adjusting the exposure times and pointing selection during observing that results in a survey of nearly uniform depth. In addition to calibrated images, the project is delivering a catalog, constructed by using a probabilistic inference-based approach to estimate source shapes and brightnesses. The catalog includes photometry from the grz optical bands and from four mid-infrared bands (at 3.4, 4.6, 12 and 22 micorons) observed by the Wide-field Infrared Survey Explorer (WISE) satellite during its full operational lifetime. The project plans two public data releases each year. All the software used to generate the catalogs is also released with the data. This paper provides an overview of the Legacy Surveys project.

We present a sample of $12$ Quasi-Stellar Objects (QSOs) potentially acting as strong gravitational lenses on background Emission Line Galaxies (ELGs) or Lyman-$\alpha$ Emitters (LAEs). The candidates are selected through a systematic search of the $350793$ QSOs spectra in the Sloan Digital Sky Survey (SDSS)-III Data Release 12 (DR12) within the Baryon Oscillation Spectroscopic Survey (BOSS). Candidates are identified by looking for compound spectra, where additional emission lines cannot be associated with the spectral features of the QSOs. The narrow diameter of BOSS fibers (2) ensures that the object responsible for the additional emission lines must lie close to the line of sight of the QSO. We focus our search on additional objects securely identified at higher redshifts than the QSOs.Among the 12 candidates identified, $9$ have definite evidence for the presence of a background ELG identified by at least $4$ higher-redshift emission lines. The remaining $3$ probable candidates present a strong asymmetrical emission line attributed to a higher-redshift LAE. The QSO-Galaxy lens candidates have QSO redshifts in the range $0.24\lesssim z_{\rm{QSO}} \lesssim 0.66$ and background galaxy redshifts in the range $0.48 \lesssim z_s \lesssim 0.94$ whereas the QSO-LAE lens candidates have QSO redshifts in the range $0.75 \lesssim z_{\rm{QSO}} \lesssim 1.23$ and source LAE redshifts in the range $2.17 \lesssim z_s \lesssim 4.48$. Upon confirmation of the lensing nature of the systems, this sample may quadruple the number of known QSOs acting as strong lenses. Future imaging of the full sample will allow to model the radial mass profile of QSO host galaxies and study the scaling relations between Super-Massive Black Holes (SMBHs) and their host galaxies.

The fourth generation of the Sloan Digital Sky Survey (SDSS-IV) has been in operation since July 2014. This paper describes the second data release from this phase, and the fourteenth from SDSS overall (making this, Data Release Fourteen or DR14). This release makes public data taken by SDSS-IV in its first two years of operation (July 2014-2016). Like all previous SDSS releases, DR14 is cumulative, including the most recent reductions and calibrations of all data taken by SDSS since the first phase began operations in 2000. New in DR14 is the first public release of data from the extended Baryon Oscillation Spectroscopic Survey (eBOSS); the first data from the second phase of the Apache Point Observatory (APO) Galactic Evolution Experiment (APOGEE-2), including stellar parameter estimates from an innovative data driven machine learning algorithm known as "The Cannon"; and almost twice as many data cubes from the Mapping Nearby Galaxies at APO (MaNGA) survey as were in the previous release (N = 2812 in total). This paper describes the location and format of the publicly available data from SDSS-IV surveys. We provide references to the important technical papers describing how these data have been taken (both targeting and observation details) and processed for scientific use. The SDSS website (www.sdss.org) has been updated for this release, and provides links to data downloads, as well as tutorials and examples of data use. SDSS-IV is planning to continue to collect astronomical data until 2020, and will be followed by SDSS-V.

We use flux-transmission correlations in forests to measure the imprint of baryon acoustic oscillations (BAO). The study uses spectra of 157,783 quasars in the redshift range 2.1≤ z ≤ 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, =c/H(z), relative to the sound horizon is (z=2.33)/r_d=9.07 ± 0.31. The best-determined combination of comoving angular-diameter distance, , and the Hubble distance is found to be ^0.7^0.3/r_d=13.94±0.35. This value is 1.028±0.026 times the prediction of the flat-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-density parameters to be =0.296 ± 0.029, =0.699 ± 0.100 and Ω_k = -0.002 ± 0.119.

We describe the algorithm used to select the emission line galaxy (ELG) sample at z similar to 0.85 for the extended Baryon Oscillation Spectroscopic Survey of the Sloan Digital Sky Survey IV, using photometric data from the DECam Legacy Survey. Our selection is based on a selection box in the g - r versus r - z colour-colour space and a cut on the g-band magnitude, to favour galaxies in the desired redshift range with strong [O II] emission. It provides a target density of 200 deg(-2) on the North Galactic Cap and of 240 deg(-2) on the South Galactic Cap (SGC), where we use a larger selection box because of deeper imaging. We demonstrate that this selection passes the extended Baryon Oscillation Spectroscopic Survey requirements in terms of homogeneity. About 50 000 ELGs have been observed since the observations have started in 2016, September. These roughly match the expected redshift distribution, though the measured efficiency is slightly lower than expected. The efficiency can be increased by enlarging the redshift range and with incoming pipeline improvement. The cosmological forecast based on these first data predict sigma D-V/D-V = 0.023, in agreement with previous forecasts. Lastly, we present the stellar population properties of the ELG SGC sample. Once observations are completed, this sample will be suited to provide a cosmological analysis at z similar to 0.85, and will pave the way for the next decade of massive spectroscopic cosmological surveys, which heavily rely on ELGs. The target catalogue over the SGC will be released along with DR14.

We present two wide-field catalogues of photometrically selected emission line galaxies (ELGs) at z approximate to 0.8 covering about 2800 deg(2)over the south galactic cap. The catalogues were obtained using a Fisher discriminant technique described in a companion paper. The two catalogues differ by the imaging used to define the Fisher discriminant: the first catalogue includes imaging from the Sloan Digital Sky Survey and the Wide-field Infrared Survey Explorer, the second also includes information from the South Galactic Cap U-band Sky Survey. Containing respectively 560 045 and 615 601 objects, they represent the largest ELG catalogues available today and were designed for the ELG programme of the extended Baryon Oscillation Spectroscopic Survey (eBOSS). We study potential sources of systematic variation in the angular distribution of the selected ELGs due to fluctuations of the observational parameters. We model the influence of the observational parameters using a multivariate regression and implement a weighting scheme which allows effective removal of all of the systematic errors induced by the observational parameters. We show that fluctuations in the imaging zero-points of the photometric bands have minor impact on the angular distribution of objects in our catalogues. We compute the angular clustering of both catalogues and show that our weighting procedure effectively removes spurious clustering on large scales. We fit a model to the small-scale angular clustering, showing that the selections have similar biases of 1.35/D-a(z) and 1.28/D-a(z). Both catalogues are publicly available.

We present the results of the first observations of the emission line galaxies (ELG) of the extended Baryon Oscillation Spectroscopic Survey. From the total 9000 targets, 4600 have been selected from the Dark Energy Survey (DES). In this subsample, the total success rate for redshifts between 0.6 and 1.2 is 71 and 68 per cent for a bright and a faint samples, respectively, including redshifts measured from a single strong emission line. The mean redshift is 0.80 for the bright and 0.87 for the faint sample, while the percentage of unknown redshifts is 15 and 13 per cent, respectively. In both cases, the star contamination is lower than 2 per cent. We evaluate how well the ELG redshifts are measured using the target selection photometry and validating with the spectroscopic redshifts measured by eBOSS. We explore different techniques to reduce the photometric redshift outliers fraction with a comparison between the template fitting, the neural networks and the random forest methods. Finally, we study the clustering properties of the DES SVA1 ELG samples. We select only the most secure spectroscopic redshift in the redshift range 0.6 < z < 1.2, leading to a mean redshift for the bright and faint sample of 0.85 and 0.90, respectively. We measure the projected angular correlation function and obtain a galaxy bias averaging on scales from 1 to 10 Mpc h(-1) of 1.58 +/- 0.10 for the bright sample and 1.65 +/- 0.12 for the faint sample. These values are representative of a galaxy population with M-B - log(h) < -20.5, in agreement with what we measure by fitting galaxy templates to the photometric data.

We describe the Sloan Digital Sky Survey IV (SDSS-IV), a project encompassing three major spectroscopic programs. The Apache Point Observatory Galactic Evolution Experiment 2 (APOGEE-2) is observing hundreds of thousands of Milky Way stars at high resolution and high signal-to-noise ratio in the near-infrared. The Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey is obtaining spatially-resolved spectroscopy for thousands of nearby galaxies (median redshift of z = 0.03). The extended Baryon Oscillation Spectroscopic Survey (eBOSS) is mapping the galaxy, quasar, and neutral gas distributions between redshifts z = 0.6 and 3.5 to constrain cosmology using baryon acoustic oscillations, redshift space distortions, and the shape of the power spectrum. Within eBOSS, we are conducting two major subprograms: the SPectroscopic IDentification of eROSITA Sources (SPIDERS), investigating X-ray AGN and galaxies in X-ray clusters, and the Time Domain Spectroscopic Survey (TDSS), obtaining spectra of variable sources. All programs use the 2.5-meter Sloan Foundation Telescope at Apache Point Observatory; observations there began in Summer 2014. APOGEE-2 also operates a second near-infrared spectrograph at the 2.5-meter du Pont Telescope at Las Campanas Observatory, with observations beginning in early 2017. Observations at both facilities are scheduled to continue through 2020. In keeping with previous SDSS policy, SDSS-IV provides regularly scheduled public data releases; the first one, Data Release 13, was made available in July 2016.

The fourth generation of the Sloan Digital Sky Survey (SDSS-IV) began observations in 2014 July. It pursues three core programs: the Apache Point Observatory Galactic Evolution Experiment 2 (APOGEE-2), Mapping Nearby Galaxies at APO (MaNGA), and the Extended Baryon Oscillation Spectroscopic Survey (eBOSS). As well as its core program, eBOSS contains two major subprograms: the Time Domain Spectroscopic Survey (TDSS) and the SPectroscopic IDentification of ERosita Sources (SPIDERS). This paper describes the first data release from SDSS-IV, Data Release 13 (DR13). DR13 makes publicly available the first 1390 spatially resolved integral field unit observations of nearby galaxies from MaNGA. It includes new observations from eBOSS, completing the Sloan Extended QUasar, Emission-line galaxy, Luminous red galaxy Survey (SEQUELS), which also targeted variability-selected objects and X-ray-selected objects. DR13 includes new reductions of the SDSS-III BOSS data, improving the spectrophotometric calibration and redshift classification, and new reductions of the SDSS-III APOGEE-1 data, improving stellar parameters for dwarf stars and cooler stars. DR13 provides more robust and precise photometric calibrations. Value-added target catalogs relevant for eBOSS, TDSS, and SPIDERS and an updated red-clump catalog for APOGEE are also available. This paper describes the location and format of the data and provides references to important technical papers. The SDSS web site, http://www.sdss.org , provides links to the data, tutorials, examples of data access, and extensive documentation of the reduction and analysis procedures. DR13 is the first of a scheduled set that will contain new data and analyses from the planned ∼6 yr operations of SDSS-IV.

In this study, we probe the transition to cosmic homogeneity in the Large Scale Structure (LSS) of the Universe using the CMASS galaxy sample of BOSS spectroscopic survey which covers the largest effective volume to date, 3 h(-3) Gpc(3) at 0.43 <= z <= 0.7. We study the scaled counts-in-spheres, N(< r), and the fractal correlation dimension, D-2(r), to assess the homogeneity scale of the universe using a Landy & Szalay inspired estimator.Defining the scale of transition to homogeneity as the scale at which D-2(r) reaches 3 within 1%, i.e. D-2(r) > 2.97 for r > R-H, we find R-H = (63.3 +/- 0.7) h(-1) Mpc, in agreement at the percentage level with the predictions of the ACDM model R-H = 62.0 h(-1) Mpc. Thanks to the large cosmic depth of the survey, we investigate the redshift evolution of the transition to homogeneity scale and find agreement with the ACDM prediction. Finally, we find that D-2 is compatible with 3 at scales larger than 300 h(-1) Mpc in all redshift bins.These results consolidate the Cosmological Principle and represent a precise consistency test of the ACDM model.

In a six-year program started in 2014 July, the Extended Baryon Oscillation Spectroscopic Survey (eBOSS) will conduct novel cosmological observations using the BOSS spectrograph at Apache Point Observatory. These observations will be conducted simultaneously with the Time Domain Spectroscopic Survey (TDSS) designed for variability studies and the Spectroscopic Identification of eROSITA Sources (SPIDERS) program designed for studies of X-ray sources. In particular, eBOSS will measure with percent-level precision the distance-redshift relation with baryon acoustic oscillations (BAO) in the clustering of matter. eBOSS will use four different tracers of the underlying matter density field to vastly expand the volume covered by BOSS and map the large-scale-structures over the relatively unconstrained redshift range 0.6 < z < 2.2. Using more than 250,000 new, spectroscopically confirmed luminous red galaxies at a median redshift z = 0.72, we project that eBOSS will yield measurements of the angular diameter distance d(A)(z) to an accuracy of 1.2% and measurements of H(z) to 2.1% when combined with the z > 0.6 sample of BOSS galaxies. With similar to 195,000 new emission line galaxy redshifts, we expect BAO measurements of d(A)(z) to an accuracy of 3.1% and H(z) to 4.7% at an effective redshift of z = 0.87. A sample of more than 500,000 spectroscopically confirmed quasars will provide the first BAO distance measurements over the redshift range 0.9 < z < 2.2, with expected precision of 2.8% and 4.2% on d(A)(z) and H(z), respectively. Finally, with 60,000 new quasars and re-observation of 60,000 BOSS quasars, we will obtain new Lya forest measurements at redshifts z > 2.1; these new data will enhance the precision of d(A)(z) and H(z) at z > 2.1 by a factor of 1.44 relative to BOSS. Furthermore, eBOSS will provide improved tests of General Relativity on cosmological scales through redshift-space distortion measurements, improved tests for non-Gaussianity in the primordial density field, and new constraints on the summed mass of all neutrino species. Here, we provide an overview of the cosmological goals, spectroscopic target sample, demonstration of spectral quality from early data, and projected cosmological constraints from eBOSS.

The BOSS quasar sample is used to study cosmic homogeneity with a 3D survey in the redshift range 2.2 < z < 2 : 8. We measure the count-in-sphere, N (< r), i. e. the average number of objects around a given object, and its logarithmic derivative, the fractal correlation dimension, D 2(r). For a homogeneous distribution N (< r) / r 3 and D 2(r) = 3. Due to the uncertainty on tracer density evolution, 3D surveys can only probe homogeneity up to a redshift dependence, i.e. they probe so-called "spatial isotropy". Our data demonstrate spatial isotropy of the quasar distribution in the redshift range 2 : 2 < z < 2 : 8 in a modelindependent way, independent of any FLRW fi ducial cosmology, resulting in 3 - (D-2) < 1.7 x 10 3 (2 sigma) over the range 250 < r < 1200 h(-1) Mpc for the quasar distribution. If we assume that quasars do not have a bias much less than unity, this implies spatial isotropy of the matter distribution on large scales. Then, combining with the Copernican principle, we fi nally get homogeneity of the matter distribution on large scales. Alternatively, using a flat ACDM fi ducial cosmology with CMB-derived parameters, and measuring the quasar bias relative to this ACDM model, our data provide a consistency check of the model, in terms of how homogeneous the Universe is on di ff erent scales. D-2(r) is found to be compatible with our ACDM model on the whole 10 < r < 1200 h(-1) Mpc range. For the matter distribution we obtain 3 - (D-2) < 5 x 10(-5) (2 sigma) over the range 250 < r < 1200 h(-1) Mpc, consistent with homogeneity on large scales.

DESI (Dark Energy Spectropic Instrument) is a Stage IV ground-based dark energy experiment that will study baryon acoustic oscillations and the growth of structure through redshift-space distortions with a wide-area galaxy and quasar redshift survey. The DESI instrument is a robotically-actuated, fiber-fed spectrograph capable of taking up to 5,000 simultaneous spectra over a wavelength range from 360 nm to 980 nm. The fibers feed ten three-arm spectrographs with resolution R= λ/Δλ between 2000 and 5500, depending on wavelength. The DESI instrument will be used to conduct a five-year survey designed to cover 14,000 deg^2. This powerful instrument will be installed at prime focus on the 4-m Mayall telescope in Kitt Peak, Arizona, along with a new optical corrector, which will provide a three-degree diameter field of view. The DESI collaboration will also deliver a spectroscopic pipeline and data management system to reduce and archive all data for eventual public use.

We present a new selection technique of producing spectroscopic target catalogues for massive spectroscopic surveys for cosmology. This work was conducted in the context of the extended Baryon Oscillation Spectroscopic Survey (eBOSS), which will use similar to 200 000 emission line galaxies (EEGs) at 0.6 < z(spec),, < 1.0 to obtain a precise baryon acoustic oscillation measurement. Our proposed selection technique is based on optical and near-infrared broad-band filter photometry. We used a training sample to define a quantity, the Fisher discriminant (linear combination of colours), which correlates best with the desired properties of the target: redshift and [OII] flux. The proposed selections are simply done by applying a cut on magnitudes and this Fisher discriminant. We used public data and dedicated SDSS spectroscopy to quantify the redshift distribution and [0111 flux of our ELG target selections. We demonstrate that two of our selections fulfil the initial eBOSS/ELG redshift requirements: for a target density' of 180 deg(-2), similar to 70% of the selected objects have 0.6 < zspec < 1.0 and only similar to 1% of those galaxies in the range 0.6 < zspec < 1.0 are expected to have a catastrophic z(spec) estimate. Additionally, the stacked spectra and stacked deep images for those two selections show characteristic features of star -forming galaxies. The proposed approach using the Fisher discriminant could, however, be used to efficiently-select other galaxy populations, based on multi-band photometry, providing that spectroscopic information is available. This technique could thus be useful for other future massive spectroscopic surveys such as PFS, DESI, and 4MOST.

Current and future large redshift surveys, as the Sloan Digital Sky Survey IV extended Baryon Oscillation Spectroscopic Survey (SDSS-IV/eBOSS) or the Dark Energy Spectroscopic Instrument (DESI), will use emission-line galaxies (ELGs) to probe cosmological models by mapping the large-scale structure of the Universe in the redshift range 0.6 < z < 1.7. With current data, we explore the halo-galaxy connection by measuring three clustering properties of g-selected ELGs as matter tracers in the redshift range 0.6 < z < 1: (i) the redshift-space two-point correlation function using spectroscopic redshifts from the BOSS ELG sample and VIPERS; (ii) the angular two-point correlation function on the footprint of the CFHT-LS; (iii) the galaxy-galaxy lensing signal around the ELGs using the CFHTLenS. We interpret these observations by mapping them on to the latest high-resolution MultiDark Planck N-body simulation, using a novel (Sub) Halo-Abundance Matching technique that accounts for the ELG incompleteness. ELGs at z similar to 0.8 live in haloes of (1 +/- 0.5) x 10(12) h(-1)M(circle dot) and 22.5 +/- 2.5 per cent of them are satellites belonging to a larger halo. The halo occupation distribution of ELGs indicates that we are sampling the galaxies in which stars form in the most efficient way, according to their stellar-to-halo mass ratio.

We describe the algorithm used to select the luminous red galaxy (LRG) sample for the extended Baryon Oscillation Spectroscopic Survey (eBOSS) of the Sloan Digital Sky Survey IV (SDSS-IV) using photometric data from both the SDSS and the Wide-field Infrared Survey Explorer. LRG targets are required to meet a set of color selection criteria and have z-band and i-band MODEL magnitudes z < 19.95 and 19.9 < i < 21.8, respectively. Our algorithm selects roughly 50 LRG targets per square degree, the great majority of which lie in the redshift range 0.6 < z < 1.0 (median redshift 0.71). We demonstrate that our methods are highly effective at eliminating stellar contamination and lower-redshift galaxies. We perform a number of tests using spectroscopic data from SDSS-III/BOSS ancillary programs to determine the redshift reliability of our target selection and its ability to meet the science requirements of eBOSS. The SDSS spectra are of high enough signal-to-noise ratio that at least similar to 89% of the target sample yields secure redshift measurements. We also present tests of the uniformity and homogeneity of the sample, demonstrating that it should be clean enough for studies of the large-scale structure of the universe at higher redshifts than SDSS-III/BOSS LRGs reached.