Citation:
Date Published:
June 1, 2009Abstract:
This paper describes the Seventh Data Release of the Sloan Digital SkySurvey (SDSS), marking the completion of the original goals of the SDSSand the end of the phase known as SDSS-II. It includes 11,663deg2 of imaging data, with most of the ~2000 deg2increment over the previous data release lying in regions of lowGalactic latitude. The catalog contains five-band photometry for 357million distinct objects. The survey also includes repeat photometry ona 120° long, 2fdg5 wide stripe along the celestial equator in theSouthern Galactic Cap, with some regions covered by as many as 90individual imaging runs. We include a co-addition of the best of thesedata, going roughly 2 mag fainter than the main survey over 250deg2. The survey has completed spectroscopy over 9380deg2 the spectroscopy is now complete over a large contiguousarea of the Northern Galactic Cap, closing the gap that was present inprevious data releases. There are over 1.6 million spectra in total,including 930,000 galaxies, 120,000 quasars, and 460,000 stars. The datarelease includes improved stellar photometry at low Galactic latitude.The astrometry has all been recalibrated with the second version of theUSNO CCD Astrograph Catalog, reducing the rms statistical errors at thebright end to 45 milliarcseconds per coordinate. We further quantify asystematic error in bright galaxy photometry due to poor skydetermination; this problem is less severe than previously reported forthe majority of galaxies. Finally, we describe a series of improvementsto the spectroscopic reductions, including better flat fielding andimproved wavelength calibration at the blue end, better processing ofobjects with extremely strong narrow emission lines, and an improveddetermination of stellar metallicities.