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Nidever D.L.,University of Michigan | Bovy J.,Institute for Advanced Study | Bird J.C.,Vanderbilt University | Andrews B.H.,Ohio State University | And 45 more authors.
Astrophysical Journal | Year: 2014

We employ the first two years of data from the near-infrared, high-resolution SDSS-III/APOGEE spectroscopic survey to investigate the distribution of metallicity and α-element abundances of stars over a large part of the Milky Way disk. Using a sample of ≈10, 000 kinematically unbiased red-clump stars with ∼5% distance accuracy as tracers, the [α/Fe] versus [Fe/H] distribution of this sample exhibits a bimodality in [α/Fe] at intermediate metallicities, -0.9 < [Fe/H] <-0.2, but at higher metallicities ([Fe/H] ∼+0.2) the two sequences smoothly merge. We investigate the effects of the APOGEE selection function and volume filling fraction and find that these have little qualitative impact on the α-element abundance patterns. The described abundance pattern is found throughout the range 5 < R < 11 kpc and 0 < |Z| < 2 kpc across the Galaxy. The [α/Fe] trend of the high-α sequence is surprisingly constant throughout the Galaxy, with little variation from region to region (∼10%). Using simple galactic chemical evolution models, we derive an average star-formation efficiency (SFE) in the high-α sequence of ∼4.5 × 10-10 yr-1, which is quite close to the nearly constant value found in molecular-gas-dominated regions of nearby spirals. This result suggests that the early evolution of the Milky Way disk was characterized by stars that shared a similar star-formation history and were formed in a well-mixed, turbulent, and molecular-dominated ISM with a gas consumption timescale (SFE-1) of ∼2 Gyr. Finally, while the two α-element sequences in the inner Galaxy can be explained by a single chemical evolutionary track, this cannot hold in the outer Galaxy, requiring, instead, a mix of two or more populations with distinct enrichment histories. © 2014. The American Astronomical Society. All rights reserved.

Furlanetto C.,Federal University of Rio Grande do Sul | Furlanetto C.,Laboratorio Interinstitucional Of E Astronomia | Santiago B.X.,Federal University of Rio Grande do Sul | Santiago B.X.,Laboratorio Interinstitucional Of E Astronomia | And 15 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2013

We present the first results of the SOAR (Southern Astrophysical Research) Gravitational Arc Survey (SOGRAS). The survey imaged 47 clusters in two redshift intervals centred at z = 0.27 and z = 0.55, targeting the richest clusters in each interval. Images were obtained in the g', r' and i' bands using the SOAR Optical Imager (SOI), with a median seeing of 0.83, 0.76 and 0.71 arcsec, respectively, in these filters. Most of the survey clusters are located within the Sloan Digital Sky Survey (SDSS) Stripe 82 region and all of them are in the SDSS footprint. Photometric calibration was therefore performed using SDSS stars located in our SOI fields. We reached for galaxies in all fields the detection limits of g ~ 23.5, r ~ 23 and i ~ 22.5 for a signal-to-noise ratio (S/N) = 3. As a byproduct of the image processing, we generated a source catalogue with 19 760 entries, the vast majority of which are galaxies,wherewe list their positions, magnitudes and shape parameters. We compared our galaxy shape measurements to those of local galaxies and concluded that they were not strongly affected by seeing. From the catalogue data, we are able to identify a red sequence of galaxies in most clusters in the lower z range. We found 16 gravitational arc candidates around eight clusters in our sample. They tend to be bluer than the central galaxies in the lensing cluster. A preliminary analysis indicates that ~10 per cent of the clusters have arcs around them, with a possible indication of a larger efficiency associated with the high-z systems when compared to the low-z ones. Deeper follow-up images with Gemini strengthen the case for the strong lensing nature of the candidates found in this survey. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.

Paris I.,University of Chile | Petitjean P.,CNRS Paris Institute of Astrophysics | Aubourg E.,University Paris Diderot | Ross N.P.,Lawrence Berkeley National Laboratory | And 54 more authors.
Astronomy and Astrophysics | Year: 2014

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, have luminosities Mi[z = 2] <-20.5 (in a ΛCDM cosmology with H0 = 70 km s-1 Mpc-1, ΩM = 0.3, and ΩΛ = 0.7), and either display at least one emission line with a full width at half maximum (FWHM) larger than 500 km s-1 or, if not, have interesting/complex absorption features. 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 6373 deg2 with robust identification and redshift measured by a combination of principal component eigenspectra. The number of quasars with z > 2.15 (117 668) is ~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 (C iv, C iii, Mg ii). 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 3600-10 500 Å at a spectral resolution in the range 1300 < R < 2500; the spectra can be retrieved from the SDSS Catalog Archive Server. We also provide a supplemental list of an additional 2376 quasars that have been identified among the galaxy targets of the SDSS-III/BOSS. © 2014 ESO.

Furlanetto C.,Federal University of Rio Grande do Sul | Furlanetto C.,Laboratorio Interinstitucional Of E Astronomia | Santiago B.X.,Federal University of Rio Grande do Sul | Santiago B.X.,Laboratorio Interinstitucional Of E Astronomia | And 10 more authors.
Astronomy and Astrophysics | Year: 2013

Simple models of gravitational arcs are crucial for simulating large samples of these objects with full control of the input parameters. These models also provide approximate and automated estimates of the shape and structure of the arcs, which are necessary for detecting and characterizing these objects on massive wide-area imaging surveys. We here present and explore the ArcEllipse, a simple prescription for creating objects with a shape similar to gravitational arcs. We also present PaintArcs, which is a code that couples this geometrical form with a brightness distribution and adds the resulting object to images. Finally, we introduce ArcFitting, which is a tool that fits ArcEllipses to images of real gravitational arcs. We validate this fitting technique using simulated arcs and apply it to CFHTLS and HST images of tangential arcs around clusters of galaxies. Our simple ArcEllipse model for the arc, associated to a Sérsic profile for the source, recovers the total signal in real images typically within 10%-30%. The ArcEllipse+Sérsic models also automatically recover visual estimates of length-to-width ratios of real arcs. Residual maps between data and model images reveal the incidence of arc substructure. They may thus be used as a diagnostic for arcs formed by the merging of multiple images. The incidence of these substructures is the main factor that prevents ArcEllipse models from accurately describing real lensed systems. © 2012 ESO.

Comparat J.,Aix - Marseille University | Jullo E.,Aix - Marseille University | Kneib J.-P.,Aix - Marseille University | Kneib J.-P.,Ecole Polytechnique Federale de Lausanne | And 20 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2013

The baryon acoustic oscillation (BAO) feature in the two-point correlation function of galaxies supplies a standard ruler to probe the expansion history of the Universe. We study here several galaxy selection schemes, aiming at building an emission-line galaxy (ELG) sample in the redshift range 0.6 < z<1.7, that would be suitable for future BAO studies, providing a highly biased galaxy sample. We analyse the angular galaxy clustering of galaxy selections at the redshifts 0.5, 0.7, 0.8, 1 and 1.2 and we combine this analysis with a halo occupation distribution (HOD) model to derive the properties of the haloes these galaxies inhabit, in particular the galaxy bias on large scales. We also perform a weak lensing analysis (aperture statistics) to extract the galaxy bias and the cross-correlation coefficient and compare to theHODprediction. We apply this analysis on a data set composed of the photometry of the deep co-addition on Sloan Digital Sky Survey (SDSS) Stripe 82 (225 deg2), of Canada-France-Hawaii Telescope/Stripe 82 deep i-band weak lensing survey and of the Wide-Field Infrared Survey Explorer infrared photometric band W1. The analysis on the SDSS-III/constant mass galaxies selection at z = 0.5 is in agreement with previous studies on the tracer, moreover we measure its cross-correlation coefficient r = 1.16 ± 0.35. For the higher redshift bins, we confirm the trends that the brightest galaxy populations selected are strongly biased (b > 1.5), but we are limited by current data sets depth to derive precise values of the galaxy bias. A survey using such tracers of the mass field will guarantee a high significance detection of the BAO. © 2013 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.

Delubac T.,CEA Saclay Nuclear Research Center | Delubac T.,Ecole Polytechnique Federale de Lausanne | Bautista J.E.,University Paris Diderot | Busca N.G.,University Paris Diderot | And 40 more authors.
Astronomy and Astrophysics | Year: 2015

We report a detection of the baryon acoustic oscillation (BAO) feature in the flux-correlation function of the Lyα 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 ≤ z ≤ 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, DA (z = 2.34) and expansion rate, H (z = 2.34), both on a scale set by the sound horizon at the drag epoch, rd. We find DA/rd = 11.28 ± 0.65(1σ)-1.2 +2.8(2σ) and DH/rd = 9.18 ± 0.28(1σ) ± 0.6(2σ) where DH = c/H. The optimal combination, ∼DH 0.7 DA 0.3/rd is determined with a precision of ∼2%. For the value rd = 147.4 Mpc, consistent with the cosmic microwave background power spectrum measured by Planck, we find DA(z = 2.34) = 1662 ± 96(1σ) Mpc and H(z = 2.34) = 222 ± 7(1σ) 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-Lyα forest cross-correlation. The autocorrelation 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 DA/rd that are 7% lower and 7% higher for DH/rd than the predictions of a flat ΛCDM cosmological model with the best-fit Planck parameters. With our estimated statistical errors, the significance of this discrepancy is ≈2.5σ. © ESO 2015.

Schultheis M.,University of Nice Sophia Antipolis | Zasowski G.,Johns Hopkins University | Allende Prieto C.,Institute of Astrophysics of Canarias | Allende Prieto C.,University of La Laguna | And 19 more authors.
Astronomical Journal | Year: 2014

Galactic interstellar extinction maps are powerful and necessary tools for Milky Way structure and stellar population analyses, particularly toward the heavily reddened bulge and in the midplane. However, due to the difficulty of obtaining reliable extinction measures and distances for a large number of stars that are independent of these maps, tests of their accuracy and systematics have been limited. Our goal is to assess a variety of photometric stellar extinction estimates, including both two-dimensional and three-dimensional extinction maps, using independent extinction measures based on a large spectroscopic sample of stars toward the Milky Way bulge. We employ stellar atmospheric parameters derived from high-resolution H-band Apache Point Observatory Galactic Evolution Experiment (APOGEE) spectra, combined with theoretical stellar isochrones, to calculate line-of-sight extinction and distances for a sample of more than 2400 giants toward the Milky Way bulge. We compare these extinction values to those predicted by individual near-IR and near+mid-IR stellar colors, two-dimensional bulge extinction maps, and three-dimensional extinction maps. The long baseline, near+mid-IR stellar colors are, on average, the most accurate predictors of the APOGEE extinction estimates, and the two-dimensional and three-dimensional extinction maps derived from different stellar populations along different sightlines show varying degrees of reliability. We present the results of all of the comparisons and discuss reasons for the observed discrepancies. We also demonstrate how the particular stellar atmospheric models adopted can have a strong impact on this type of analysis, and discuss related caveats. © 2014. The American Astronomical Society. All rights reserved.

Ross A.J.,University of Portsmouth | Percival W.J.,University of Portsmouth | Carnero A.,Observatorio Nacional | Carnero A.,Laboratorio Interinstitucional Of E Astronomia | And 41 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2013

We analyse the density field of 264 283 galaxies observed by the Sloan Digital Sky Survey (SDSS)-III Baryon Oscillation Spectroscopic Survey (BOSS) and included in the SDSS Data Release 9 (DR9). In total, the SDSS DR9 BOSS data include spectroscopic redshifts for over 400 000 galaxies spread over a footprint of more than 3000 deg2. We measure the power spectrum of these galaxies with redshifts 0.43 < z < 0.7 in order to constrain the amount of local non-Gaussianity, f localNL, in the primordial density field, paying particular attention to the impact of systematic uncertainties. The BOSS galaxy density field is systematically affected by the local stellar density and this influences the ability to accurately measure f local NL. In the absence of any correction, we find (erroneously) that the probability that f local NL is greater than zero, P(f local NL > 0), is 99.5 per cent. After quantifying and correcting for the systematic bias and including the added uncertainty, we find -45 < flocalNL < 195 at 95 per cent confidence and P(f localNL > 0) = 91.0 per cent. A more conservative approach assumes that we have only learnt the k dependence of the systematic bias and allows any amplitude for the systematic correction; we find that the systematic effect is not fully degenerate with that of f localNL, and we determine that -82 < flocalNL < 178 (at 95 per cent confidence) and P(f localNL > 0) = 68 per cent. This analysis demonstrates the importance of accounting for the impact of Galactic foregrounds on f local NL measurements. We outline the methods that account for these systematic biases and uncertainties. We expect our methods to yield robust constraints on f localNL for both our own and future large-scale structure investigations. © 2012 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.

Schuler S.C.,National Optical Astronomy Observatory | Cunha K.,National Optical Astronomy Observatory | Cunha K.,University of Arizona | Smith V.V.,National Optical Astronomy Observatory | And 5 more authors.
Astrophysical Journal Letters | Year: 2011

Results of a detailed abundance analysis of the solar twins 16CygA and 16CygB based on high-resolution, high signal-to-noise ratio echelle spectroscopy are presented. 16CygB is known to host a giant planet while no planets have yet been detected around 16CygA. Stellar parameters are derived directly from our high-quality spectra, and the stars are found to be physically similar, with ΔT eff = +43K, Δlog g = -0.02dex, and Δξ = +0.10kms-1 (in the sense of A - B), consistent with previous findings. Abundances of 15 elements are derived and are found to be indistinguishable between the two stars. The abundances of each element differ by ≤0.026dex, and the mean difference is +0.003 ± 0.015 (σ)dex. Aside from Li, which has been previously shown to be depleted by a factor of at least 4.5 in 16CygB relative to 16CygA, the two stars appear to be chemically identical. The abundances of each star demonstrate a positive correlation with the condensation temperature of the elements (T c); the slopes of the trends are also indistinguishable. In accordance with recent suggestions, the positive slopes of the [m/H]-T c relations may imply that terrestrial planets have not formed around either 16CygA or 16CygB. The physical characteristics of the 16Cyg system are discussed in terms of planet formation models, and plausible mechanisms that can account for the lack of detected planets around 16CygA, the disparate Li abundances of 16CygA and B, and the eccentricity of the planet 16CygB b are suggested. © 2011. The American Astronomical Society. All rights reserved.

Seo H.-J.,University of California at Berkeley | Ho S.,Lawrence Berkeley National Laboratory | Ho S.,Carnegie Mellon University | White M.,Lawrence Berkeley National Laboratory | And 35 more authors.
Astrophysical Journal | Year: 2012

We measure the acoustic scale from the angular power spectra of the Sloan Digital Sky Survey III (SDSS-III) Data Release 8 imaging catalog that includes 872, 921 galaxies over ∼10,000 deg2 between 0.45 < z < 0.65. The extensive spectroscopic training set of the Baryon Oscillation Spectroscopic Survey luminous galaxies allows precise estimates of the true redshift distributions of galaxies in our imaging catalog. Utilizing the redshift distribution information, we build templates and fit to the power spectra of the data, which are measured in our companion paper, to derive the location of Baryon acoustic oscillations (BAOs) while marginalizing over many free parameters to exclude nearly all of the non-BAO signal. We derive the ratio of the angular diameter distance to the sound horizon scale DA (z)/rs = 9.212+0.416 - 0.404 at z = 0.54, and therefore DA (z) = 1411 ± 65 Mpc at z = 0.54; the result is fairly independent of assumptions on the underlying cosmology. Our measurement of angular diameter distance DA (z) is 1.4σ higher than what is expected for the concordance ΛCDM, in accordance to the trend of other spectroscopic BAO measurements for z ≳ 0.35. We report constraints on cosmological parameters from our measurement in combination with the WMAP7 data and the previous spectroscopic BAO measurements of SDSS and WiggleZ. We refer to our companion papers (Ho et al.; de Putter et al.) for investigations on information of the full power spectrum. © 2012. The American Astronomical Society. All rights reserved..

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