The sixth data release of the sloan digital sky survey

TLDR: The Sixth Data Release of the Sloan Digital Sky Survey (SDS) is now complete and includes much more extensive stellar spectroscopy than previously, and also includes detailed estimates of stellar temperatures, gravities, and metallicities as mentioned in this paper.

Abstract: With the Sixth Data Release of the Sloan Digital Sky Survey, the imaging of the Northern Galactic Cap is now complete. The survey contains images and parameters of roughly 287 million objects over 9583 deg^2, and 1.27 million spectra of stars, galaxies, quasars and blank sky (for sky subtraction) selected over 7425 deg^2. This release includes much more extensive stellar spectroscopy than previously, 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, giving a 0.35 mag change in the spectrophotometric flux scale. 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. (Abridged)

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TABLE 2 SEGUE Targeting Algorithms

TABLE 1 Coverage and Contents of DR6

Fig. 4.—Distribution of differences between r-band photometry synthesized from SDSS spectra ( labeled SPECTRO), and PSF and fiber magnitudes, for stars and galaxies; results are shown for DR6 (left) and the previous version of the calibration available in DR5 (right). Only objects with PSFmagnitude brighter than 19 are shown. The most important difference is the offset of 0.35 mag between the two, due to the change in calibration from fiber to PSF photometry. Each panel includes the mean and standard deviation of the best-fit Gaussian, aswell as the number of objects lying beyond 3 (as ameasure of the non-Gaussianity of the tails). Results are shown for r band, but g- and i-band results are very similar.

TABLE 5 Outputs of the specBS Pipeline Made Available in the DR6 CAS

Fig. 2.—Stripe 82, the equatorial stripe in the south Galactic cap, has been imaged multiple times. The bottom pair of curves show the number of scans covering a given right ascension in the north and south strip through the fall of 2004 (these data were also included in DR5); these data are available through the DAS. Since that time, stripe 82 has been covered many more times as part of a comprehensive survey for 0:05 < z < 0:35 supernovae, although often in conditions of poor seeing, bright moon, and /or clouds; the numbers of additional scans at each right ascension in the north and south strip are indicated in the upper pair of curves. These latter data have not been flux-calibrated. [See the electronic edition of the Supplement for a color version of this figure.]

Fig. 3.—Effects of sky subtraction errors on the photometry of bright galaxies. Top: Error in the r-band model magnitude of simulated galaxies with an n ¼ 1 (exponential) profile (blue hexagons) and an n ¼ 4 (de Vaucouleurs) profile (red crosses) as determined by the photometric pipeline, as a function of magnitude. There are 15 galaxies simulated at each magnitude for each profile. Also shown are the analogous results from J. B. Hyde & M. Bernardi (2007, unpublished) for three early-type galaxy samples: 54 nearby (z < 0:03) early-type galaxies from the ENEAR catalog (da Costa et al. 2000) in black; 280 brightest cluster galaxies from the C4 catalog (Miller et al. 2005) in green; and 9000 early-type galaxies from the Bernardi et al. (2003a) analysis in magenta. Bottom: Fractional error in the scale size re as a function of magnitude from the simulations and the J. B. Hyde & M. Bernardi analysis.