The Sloan Digital Sky Survey (SDSS) will provide the data to support detailed investigations of the distribution of luminous and non- luminous matter in the Universe: a photometrically and astrometrically calibrated digital imaging survey of pi steradians above about Galactic latitude 30 degrees in five broad optical bands to a depth of g' about 23 magnitudes, and a spectroscopic survey of the approximately one million brightest galaxies and 10^5 brightest quasars found in the photometric object catalog produced by the imaging survey. This paper summarizes the observational parameters and data products of the SDSS, and serves as an introduction to extensive technical on-line documentation.Comment: 9 pages, 7 figures, AAS Latex. To appear in AJ, Sept 200
We use numerical simulations to examine the substructure within galactic and cluster mass halos that form within a hierarchical universe. Clusters are easily reproduced with a steep mass spectrum of thousands of substructure clumps that closely matches the observations. However, the survival of dark matter substructure also occurs on galactic scales, leading to the remarkable result that galaxy halos appear as scaled versions of galaxy clusters. The model predicts that the virialized extent of the Milky Way's halo should contain about 500 satellites with circular velocities larger than the Draco and Ursa Minor systems, i.e., bound masses տ10 8 M , and tidally limited sizes տ1 kpc. The substructure clumps are on orbits that take a large fraction of them through the stellar disk, leading to significant resonant and impulsive heating. Their abundance and singular density profiles have important implications for the existence of old thin disks, cold stellar streams, gravitational lensing, and indirect/ direct detection experiments.
Using a catalog of 147,986 galaxy redshifts and fluxes from the Sloan Digital Sky Survey (SDSS), we measure the galaxy luminosity density at z ¼ 0:1 in five optical bandpasses corresponding to the SDSS bandpasses shifted to match their rest-frame shape at z ¼ 0:1. We denote the bands 0.1 u, 0.1 g, 0.1 r, 0.1 i, 0.1 z with eff ¼ ð3216; 4240; 5595; 6792; 8111 GÞ, respectively. To estimate the luminosity function, we use a maximum likelihood method that allows for a general form for the shape of the luminosity function, fits for simple luminosity and number evolution, incorporates the flux uncertainties, and accounts for the flux limits of the survey. We find luminosity densities at z ¼ 0:1 expressed in absolute AB magnitudes in a Mpc 3 to be (À14:10 AE 0:15, À15:18 AE 0:03, À15:90 AE 0:03, À16:24 AE 0:03, À16:56 AE 0:02) in ( 0.1 u, 0.1 g, 0.1 r, 0.1 i, 0.1 z), respectively, for a cosmological model with 0 ¼ 0:3, à ¼ 0:7, and h ¼ 1 and using SDSS Petrosian magnitudes. Similar results are obtained using Sérsic model magnitudes, suggesting that flux from outside the Petrosian apertures is not a major correction. In the 0.1 r band, the best-fit Schechter function to our results has à ¼ ð1:49 AE 0:04Þ Â 10 À2 h 3 Mpc À3 , M à À 5 log 10 h ¼ À20:44 AE 0:01, and ¼ À1:05 AE 0:01. In solar luminosities, the luminosity density in 0.1 r is ð1:84 AE 0:04Þ Â 10 8 h L 0:1 r; Mpc À3 . Our results in the 0.1 g band are consistent with other estimates of the luminosity density, from the Two-Degree Field Galaxy Redshift Survey and the Millennium Galaxy Catalog. They represent a substantial change ($0.5 mag) from earlier SDSS luminosity density results based on commissioning data, almost entirely because of the inclusion of evolution in the luminosity function model.
The Sloan Digital Sky Survey (SDSS) is an imaging and spectroscopic survey that will eventually cover approximately one-quarter of the celestial sphere and collect spectra of %10 6 galaxies, 100,000 quasars, 30,000 stars, and 30,000 serendipity targets. In 2001 June, the SDSS released to the general astronomical community its early data release, roughly 462 deg 2 of imaging data including almost 14 million detected objects and 54,008 follow-up spectra. The imaging data were collected in drift-scan mode in five bandpasses (u, g, r, i, and z); our 95% completeness limits for stars are 22.0, 22.2, 22.2, 21.3, and 20.5, respectively. The photometric calibration is reproducible to 5%, 3%, 3%, 3%, and 5%, respectively. The spectra are flux-and wavelength-calibrated, with 4096 pixels from 3800 to 9200 Å at R % 1800. We present the means by which these data are distributed to the astronomical community, descriptions of the hardware used to obtain the data, the software used for processing the data, the measured quantities for each observed object, and an overview of the properties of this data set.
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