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Spectra and parameters on the Science Archive Server

Access tools

See the description of DR8 data access for a full listing of the tools available. Users primarily interested in catalog parameters (redshift, metallicity, etc.) should use the CAS. Users who are interested primarily in the spectra themselves are encouraged to use the Science Archive Server.

In a nutshell, Catalog Archive Server (CAS) and CASJobs provide interfaces to a SQL database with all of the SDSS spectroscopic results. The simplest place to start is the spectroscopic query form. A SEGUE SQL cookbook, with some example queries to get you started is here

The SAS has same spectroscopic results available for browsing on the web, through its spectrum search page. This page allows the individual and bulk searches for spectra and retrieval of FITS-format versions of the spectra. It also provides an interactive visual interfacce to the spectra. For users interested in a small number of spectra (hundreds to a few thousand), we recommend that interface. For users interested in all or most of the spectra, we recommend the wget and rsync tools, as described on the Data Access page.

Outline of tables

The major spectroscopic results are contained in a few different files (on SAS) and database tables (in CAS), listed below. In the case of the SAS files, the large FITS files are all line-by-line matched, so that the Nth entry in any file refers to the same object. The "plates" file, listed first below, is especially useful as a full list of the plates released. Note that the links into SAS below bring you into the full directory tree; it is best not to wander there before first understanding the spectroscopy basics and understanding how to use the data model.

SAS locationCAS tableDescription
plates-dr8.fits(2.6 Mb)
(in SPECTRO_REDUX; see datamodel)
plateX List of all DR8 plates
(available as Yanny file too)
specObj-dr8.fits (2.2 Gb)
(in SPECTRO_REDUX;(see datamodel)
(only primaries)
Redshifts and classifications of all SDSS spectra
ssppOut-dr8.fits (1.6 Gb)
(in SSPP_REDUX; see datamodel)
sppParams Stellar parameters from SSPP
ssppOut-dr8.lineindex.fits (2.4 Gb)
(in SSPP_REDUX; see datamodel)
sppLines Stellar line indices from SSPP
photoPlate-dr8.fits (5.5 Gb)
(in SPECTRO_REDUX; see datamodel)
join on photoObj Photometric flux-based matches
photoPosPlate-dr8.fits (5.5 Gb)
(in SPECTRO_REDUX; see datamodel)
join on photoObj Photometric position-based matches
photoMatchPlate-dr8.fits (255 Mb)
(in SPECTRO_REDUX; see datamodel)
details of match results
galSpecInfo-dr8.fits (364 Mb)
(in SPECTRO_REDUX; see datamodel)
galSpecInfo Information for each galaxy processed by Garching group
galSpecIndx-dr8.fits (1.9 Gb)
(in SPECTRO_REDUX; see datamodel)
galSpecIndx Index measurements for each galaxy
galSpecLine-dr8.fits (1.7 Gb)
(in SPECTRO_REDUX; see datamodel)
galSpecLine Line measurements for each galaxy
galSpecExtra-dr8.fits (339 Mb)
(in SPECTRO_REDUX; see datamodel)
galSpecExtra Extra physical parameters for each galaxy
see datamodel)

Individual spectra for each observation of each plate
specObjAll PNG images of each spectrum