Browsing by Author "Allam, Sahar S"

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    The seventh data release of the sloan digital sky survey
    (2009) Abazajian, Kevork N; Adelman‐McCarthy, Jennifer K; AgYeros, Marcel A; Allam, Sahar S; Prieto, Carlos Allende; An, Deokkeun; Anderson, Kurt S J; Anderson, Scott F; Annis, James; Bahcall, Neta A; Bailer‐Jones, C A L; Barentine, J C; Bassett, Bruce A; Becker, Andrew C; Beers, Timothy C; Bell, Eric F; Belokurov, Vasily; Berlind, Andreas A; Berman, Eileen F; Bernardi, Mariangela; Bickerton, Steven J; Bizyaev, Dmitry; Blakeslee, John P; Blanton, Michael R; Bochanski, John J; Boroski, William N; Brewington, Howard J; Brinchmann, Jarle; Brinkmann, J; Brunner, Robert J; Budavári, Tamás; Carey, Larry N
    This paper describes the Seventh Data Release of the Sloan Digital Sky Survey (SDSS), marking the completion of the original goals of the SDSS and the end of the phase known as SDSS-II. It includes 11, 663 deg2 of imaging data, with most of the ~2000 deg2 increment over the previous data release lying in regions of low Galactic latitude. The catalog contains five-band photometry for 357 million distinct objects. The survey also includes repeat photometry on a 120° long, 2fdg5 wide stripe along the celestial equator in the Southern Galactic Cap, with some regions covered by as many as 90 individual imaging runs. We include a co-addition of the best of these data, going roughly 2 mag fainter than the main survey over 250 deg2. The survey has completed spectroscopy over 9380 deg2 the spectroscopy is now complete over a large contiguous area of the Northern Galactic Cap, closing the gap that was present in previous data releases. There are over 1.6 million spectra in total, including 930, 000 galaxies, 120, 000 quasars, and 460, 000 stars. The data release includes improved stellar photometry at low Galactic latitude. The astrometry has all been recalibrated with the second version of the USNO CCD Astrograph Catalog, reducing the rms statistical errors at the bright end to 45 milliarcseconds per coordinate. We further quantify a systematic error in bright galaxy photometry due to poor sky determination ; this problem is less severe than previously reported for the majority of galaxies. Finally, we describe a series of improvements to the spectroscopic reductions, including better flat fielding and improved wavelength calibration at the blue end, better processing of objects with extremely strong narrow emission lines, and an improved determination of stellar metallicities.
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    The sixth data release of the Sloan digital sky survey
    (2008) Adelman‐McCarthy, Jennifer K; AgYeros, Marcel A; Allam, Sahar S; Allende Prieto, Carlos; Anderson, Kurt S J; Anderson, Scott F; Annis, James; Bahcall, Neta A; Bailer‐Jones, C A L; Baldry, Ivan K; Barentine, J C; Bassett, Bruce A; Becker, Andrew C; Beers, Timothy C; Bell, Eric F; Berlind, Andreas A; Bernardi, Mariangela; Blanton, Michael R; Bochanski, John J; Boroski, William N; Brinchmann, Jarle; Brinkmann, J; Brunner, Robert J; Budavári, Tamás; Carliles, Samuel; Carr, Michael A; Castander, Francisco J; Cinabro, David; Cool, R J; Covey, Kevin R; Csabai, István; Cunha, Carlos E
    This paper describes the Sixth Data Release of the Sloan Digital Sky Survey. With this data release, the imaging of the northern Galactic cap is now complete. The survey contains images and parameters of roughly 287 million objects over 9583 deg2 , including scans over a large range of Galactic latitudes and longitudes. The survey also includes 1.27 million spectra of stars, galaxies, quasars, and blank sky (for sky subtraction) selected over 7425 deg2 . This release includes much more stellar spectroscopy than was available in previous data releases and also includes detailed estimates of stellar temperatures, gravities, and metallicities. The results of improved photometric calibration are now available, with uncertainties of roughly 1% in g, r, i, and z, and 2% in u, substantially better than the uncertainties in previous data releases. The spectra in this data release have improved wavelength and flux calibration, especially in the extreme blue and extreme red, leading to the qualitatively better determination of stellar types and radial velocities. The spectrophotometric fluxes are now tied to point-spread function magnitudes of stars rather than fiber magnitudes. This gives more robust results in the presence of seeing variations, but also implies a change in the spectrophotometric scale, which is now brighter by roughly 0.35 mag. Systematic errors in the velocity dispersions of galaxies have been fixed, and the results of two independent codes for determining spectral classifications and redshifts are made available. Additional spectral outputs are made available, including calibrated spectra from individual 15 minute exposures and the sky spectrum subtracted from each exposure. We also quantify a recently recognized underestimation of the brightnesses of galaxies of large angular extent due to poor sky subtraction; the bias can exceed 0.2 mag for galaxies brighter than r ¼ 14 mag.