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Sloan Digital Sky Survey (SDSS) I 期的数据结构介绍

Sloan Digital Sky Survey (SDSS) I 期的数据结构介绍. 沈世银 Sloan 数据挖掘研讨会 ,2006, 上海. Overview of SDSS. Image and spectroscopy survey of more than a quarter of the sky in optical bands. Survey telescope: 2.5m diameter, 3 degree field Photometry: Drift scan, u,g,r,i,z bands

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Sloan Digital Sky Survey (SDSS) I 期的数据结构介绍

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  1. Sloan Digital Sky Survey(SDSS) I期的数据结构介绍 沈世银 Sloan数据挖掘研讨会,2006,上海

  2. Overview of SDSS • Image and spectroscopy survey of more than a quarter of the sky in optical bands. • Survey telescope: 2.5m diameter, 3 degree field • Photometry: Drift scan, u,g,r,i,z bands • fiber spectra: 640 fibers per plate.

  3. Photometry • 5x6 CCDs 2048x2048pixels, 0.4arcsec per pixel • Drift scan exposure time: 54s • 5 bands (u,g,r,i,z) centered at (3540 4770 6230 7630 9130)Å • Complete to (22.0 22.2 22.2 21.3 20.5)mag

  4. Spectroscopy • 640 fibers 320x2 spectrographs • fiber diameter: 3 arcsec • fiber collision: 55 arcsec • Coverage: blue(3800-6150Å) and red(5800-9200Å) • Pixel size: 69km/s • Resolution: (/)~1800 • Exposure time 45min, (S/N)2>15 pixel-1 at g¼20.2

  5. Unique ID of SDSS objects • Photometric object • Run rerun camcol field id • Each stripe has at least two runs • Rerun: different software version • Camera column • Spectroscopic object • PlateID mjd fiberID

  6. Main scientific goals of SDSS • Main galaxy sample • Spectra of all galaxies brighter than r<17.77 • Median z ~0.1 • Luminous red galaxy • Volume complete sample for large scale • Quasars • Multi-color selection technique, UV excess feature, complete sample for i<19.1 at z<3.

  7. SDSS I data products: DR5 • 8000 sq. deg image • 215 million unique objects • 5740 sq. deg. Spectroscopy • ~680,000 galaxies • ~150,000LRGs • ~90,000 Quasars • ~150,000stars

  8. SDSS data access • Catalogue Archive Server(CAS) • http://cas.sdss.org/astrodr5/en/ • Different ways(web interface), search by object ID, position, photometry/spectroscopic parameters etc. • Data Archive Server • images of the night sky ("corrected frames") in fits and jpeg format (9.0TB) • calibrated object lists with photometric parameters as fits binary tables (1.8TB) • reduced spectra and spectral parameters as fits binary tables and ps/gif plots • calibrated spectra ("2d") 60GB • spectra, redshifts, line measurements ("1d")170 GB

  9. Data in catalogue: 3.6 TB • Photometry catalogue, output from photo pipeline • Position, ID, target information • Petrosian quantities: Petrosian magnitude, R50, R90 • constant fraction of total light, independent on redshift, suitable for galaxies • Circular aperture • PSF magnitude, isophoto magnitude • model magnitudes etc • PSF convolved, 2-dimensional model fitting (axis ratio, position angle ) • Exponential profile & De Vaucolerurs profile, composite model • Radial profile: ProfMean, azimuthally averaged surface brightness in a series of fixed annuli

  10. Some notes • Target VS Best objects • Target: Photo output for spectroscopy target • Best: Updated version of Photo output • Point – extended source? • PSFmag – PetroMag > 0.3 • Spectroscopy catalogue • Target and tile ID • Important for large scale structure study • Redshift, spectral classes, fiber magnitudes • Line measurement is not available in official catalogue, but has been done by a lot of collaborators. Is also available at the web-Interface

  11. SDSS data: images and spectra • http://das.sdss.org/

  12. Value added catalogue • http://www.sdss.org/dr5/products/value_added/index.html • NYU Value-Added Galaxy Catalog (DR4) • Low redshift sample • K correction • Sersic fitting • Large scale structure sample • Multi wavelength match: 2MASS, GALEX, spitzer, 2df, RC3, PSCz • MPA/JHU value-added galaxy catalog (DR4) • Stellar masses, • Star formation rate • Gas phase metallicities

  13. SDSS Quasar Catalog (DR3) Schneider et al. 2005, 46000 quasars • ROSAT/FIRST match (Shen et al. 2006) • CMU-PITT SDSS Value Added Catalog (VAC) database (DR3) • scientific analyses on the SDSS spectroscopic galaxy data (i.e. emission line-widths) • Group cluster catalogue • Berlind groups, DR2(http://cosmo.nyu.edu/aberlind/Groups/) • Yang groups(http://www.astro.umass.edu/xhyang/Group.html) • C4 cluster catalogue(http://www.ctio.noao.edu/~chrism/c4/) • 748 clusters • White Dwarf catalog (DR4) • 9316 spectroscopically confirmed white dwarfs and 928 hot subdwarfs. • 3rd release SDSS Moving Object Catalog (MOC) • 204,305 moving objects observed prior to June 2004

  14. Thanks！

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