About the Data
The Catalog Archive Server (CAS) provides access to the database that contains the object catalogs and related data from the Sloan Digital Sky Survey-III (SDSS-III). It is a companion to the Science Archive Server (SAS), which allows users to download raw (FITS) images and spectra from the survey. The SkyServer provides the Web interface to the CAS database. This page describes the database organization and structure.
Overview of Data Organization
The SDSS Catalog Data Model
The SDSS catalog data is stored in a commercial relational database management system (DBMS) - Microsoft's SQL Server. The data is therefore organized in several 2-dimensional tables. The tables and their relationships to each other are referred to as the schema in database jargon. The Schema link in the menubar above takes you to the Schema page where you can browse the database schema.
Diagrammatic view of the DR15 schema Database schema
There are 3 different types of data in the tables - imaging data is in the photo group of tables, spectroscopic and tiling data is in the spectro tables, and other data such as documentation or other information about the photo and spectro data, i.e. metadata, is in the meta tables. Some tables are also created specifically for speed or convenience, for example the SpecPhotoAll table, which contains a pre-computed JOIN of relevant fields in the PhotoObjAll and SpecObjAll tables.
The important tables are described below, along with the views that are currently defined on each table. A view is a subset of the corresponding table that can be used instead of the table - in other words it is a virtual table. A view is usually faster than using the base table, since it only loads a subset of the objects, but more importantly, the views we have defined on the tables select only the objects that are important for science, and they filter out non-science objects such as sky, QA or defective observations. As such, even though we list the base tables for completeness below, in the vast majority of the cases, you should use the views defined on the tables instead of the tables themselves, e.g. use the PhotoObj and SpecObj views for science instead of the PhotoObjAll and SpecObjAll tables.
Imaging (Photo) Data Tables
The important tables and views are described below. For each table, the views and indices are defined on that table are described in brief. For more information, please see the Table Descriptions help page and the Schema Browser.
By far the largest table in the database, PhotoObjAll contains the 100+ parameters for each imaging (photo) object. For most of these parameters, there are actually 5 rows each, one for each wavelength band. This table includes data on all photo objects, not just science objects, hence the name PhotoObjAll. The view of this table that includes only science objects and excludes sky and other unknown objects is the PhotoObj view. The PhotoObjAll table is there for completeness, but science queries are usually done on the PhotoObj view.
|PhotoFamily||These are in PhotoObj, but neither PhotoPrimary or Photosecondary.||These objects are generated if they are neither primary nor secondary survey objects but a composite object that has been deblended or the part of an object that has been deblended wrongfully (like the spiral arms of a galaxy). These objects are kept to track how the deblender is working. It inherits all members of the PhotoObj class.|
|PhotoObj||All primary and secondary objects in the PhotoObjAll table, which contains all the attributes of each photometric (image) object.||It selects PhotoObj with mode=1 or 2.|
|PhotoPrimary||These objects are the primary survey objects.||Each physical object on the sky has only one primary object associated with it. Upon subsequent observations secondary objects are generated. Since the survey stripes overlap, there will be secondary objects for over 10% of all primary objects, and in the southern stripes there will be a multitude of secondary objects for each primary (i.e. reobservations).|
|PhotoSecondary||Secondary objects are reobservations of the same primary object.|
|PhotoTag||The most popular columns from PhotoObjAll.||This view contains the most popular columns from the PhotoObjAll table, and is intended to enable faster queries if they only request these columns by making use of the cache. Performance is also enhanced by an index covering the columns in this view in the base table (PhotoObjAll).|
|Index Type||Key or Field List|
|covering index||mode, cy, cx, cz, htmID, type, flags, ra, dec, u, g, r, i, z|
|covering index||htmID, cx, cy, cz, type, mode, flags, ra, dec, u, g, r, i, z|
|covering index||htmID, run, camcol, field, rerun, type, mode, flags, cx, cy, cz, g, r|
|covering index||field, run, rerun, camcol, type, mode, flags, rowc, colc, ra, dec, u, g, r, i, z|
|covering index||fieldID, objID, ra, dec, r, type, flags|
|covering index||SpecObjID, cx, cy, cz, mode, type, flags, ra, dec, u, g, r, i, z|
|covering index||cx, cy, cz, htmID, mode, type, flags, ra, dec, u, g, r, i, z|
|covering index||run, mode, type, flags, u, g, r, i, z, Err_u, Err_g, Err_r, Err_i, Err_z|
|covering index||run, camcol, rerun, type, mode, flags, ra, dec, fieldID, field, u, g, r, i, z|
|covering index||run, camcol, field, mode, parentID, q_r, q_g, u_r, u_g, fiberMag_u, fiberMag_g, fiberMag_r, fiberMag_i, fiberMag_z|
|covering index||run, camcol, type, mode, cx, cy, cz|
|covering index||ra, [dec], type, mode, flags, u, g, r, i, z, psfMag_u, psfMag_g, psfMag_r, psfMag_i, psfMag_z|
|covering index||b, l, type, mode, flags, u, g, r, i, z, psfMag_u, psfMag_g, psfMag_r, psfMag_i, psfMag_z|
|covering index||parentid, mode, type|
This table contains all the measured parameters of each imaging field (offsite), along with relevant summary statistics, and astrometric and photometric information.
|Index Type||Key or Field List|
|covering index||field, camcol, run, rerun|
|covering index||run, camcol, field, rerun|
This table contains the light profiles of SDSS photo objects.
|Index Type||Key or Field List|
|primary key||objID, bin, band|
This table contains the light profiles of SDSS field objects.
|Index Type||Key or Field List|
|primary key||fieldID, bin, band|
SDSS objects within 0.5 arcmins and their match parameters are stored here. Make sure to filter out unwanted PhotoObj, like secondaries.
|Index Type||Key or Field List|
|primary key||objID, NeighborObjID|
First, RC3, Rosat, TwoMASS, TwoMASSXSC and Usno
These tables contain matches between the FIRST, RC3, ROSAT, 2MASS, 2MASSXSC (2MASS Extended Source Catalog) and USNO survey objects respectively and SDSS.
Spectro/Tiling/GalSpec/SPP Data TablesThe important spectro, tiling, galSpec and spp (Stellar Parameter Pipeline) data tables are described here. The tiling table names are prefixed by "sdss" to distinguish them from tiling tables for BOSS (Baryon Oscillation Spectroscopic Survey) data in the future. For more information, please see the Table Descriptions help page and the Schema Browser. PlateX - This table contains data as exported (the X is for exported) from a given plate used for spectroscopic observations. Each plate has 640 observed spectra and hence 640 corresponding entries in SpecObjAll. PlateX Indices: Index Type Key or Field List primary key plateID covering index htmID, ra, dec, cx, cy, cz SpecObjAll - This is a base table containing ALL the spectroscopic information, including a lot of duplicate and bad data. Use the SpecObj view instead (see below), which has the data properly filtered for cleanliness. SpecObjAll Views: View Name Contents Description SpecObj A view of Spectro objects that just has the clean spectra. The view excludes QA and Sky and duplicates. Use this as the main way to access the spectro objects. SpecObjAll Indices: Index Type Key or Field List primary key specObjID foreign key PlateX(plateID) covering index htmID, ra, dec, cx, cy, cz, sciencePrimary covering index BestObjID, sourceType, sciencePrimary, class, htmID, ra, dec, plate, mjd, fiberid, z, zErr covering index class, zWarning, z, sciencePrimary, plateId, bestObjID, targetObjId, htmID, ra, dec covering index targetObjID, sourceType, sciencePrimary, class, htmID, ra, dec covering index ra, [dec], class, plate, tile, z, zErr, sciencePrimary, plateID, bestObjID covering index fluxObjID SpecPhotoAll - The combined spectro and photo parameters of an object in SpecObjAll. This is a precomputed join between the PhotoObjAll and SpecObjAll tables. The photo attributes included cover about the same as in the PhotoTag view. The table also includes certain attributes from the Tile table. SpecPhotoAll Views: View Name Contents Description SpecPhoto A view of joined Spectro and Photo objects that have the clean spectra. The view includes only those pairs where the SpecObj is a sciencePrimary, and the BEST PhotoObj is a PRIMARY (mode=1). SpecPhotoAll Indices: Index Type Key or Field List primary key specObjID foreign key SpecObjAll(specObjID) covering index objID, sciencePrimary, class, z, targetObjid covering index targetObjID, sciencePrimary, class, z, objid sdssTileAll - Contains information about individual tiles (offsite) on the sky. sdssTileAll Views: View Name Contents Description sdssTile A view of sdssTileAll that have untiled=0 The view excludes those sdssTiles that have been untiled. sdssTileAll Indices: Index Type Key or Field List primary key tile foreign key sdssTilingRun(tileRun) covering unique index tileRun, tile covering index htmID, racen, deccen, cx, cy, cz sdssTiledTargetAll - This table stores information that keeps track of why a target (offsite) was assigned to a tile (offsite). sdssTiledTargetAll Views: None found sdssTiledTargetAll Indices: Index Type Key or Field List primary key targetID covering index htmID, ra, dec, cx, cy, cz sdssTilingGeometry - This table contains geometrical information about tiling regions, including tiling boundaries. The TileBoundary view serves up the boundaries. sdssTilingGeometry Views: View Name Contents Description sdssTilingBoundary A view of sdssTilingGeometry objects that have isMask = 0 The view excludes those sdssTilingGeometry objects that have isMask = 1. See also sdssTilingMask. sdssTilingMask A view of sdssTilingGeometry objects that have isMask = 1 The view excludes those sdssTilingGeometry objects that have isMask = 0. See also sdssTilingBoundary. sdssTilingGeometry Indices: Index Type Key or Field List primary key tilingGeometryID foreign key sdssTilingRun(tileRun) sdssTilingRun - Contains basic information about each run of the tiling software. sdssTilingInfo - Contains information on what happened to a Target in a run of tiling software. galSpecExtra, galSpecIndx, galSpecInfo and galSpecLine- These tables contain the estimated physical parameters, the spectral index measurements, general information about the spectroscopic analysis and the emission line measurements from the MPA-JHU spectroscopic catalog. galSpecExtra Indices: Index Type Key or Field List primary key specObjID galSpecIndx Indices: No indices defined on this table galSpecInfo Indices: Index Type Key or Field List primary key specObjID galSpecLine Indices: Index Type Key or Field List primary key specObjID sppLines and sppParams- These tables contain the line and parameter measurements from the Stellar Parameter Pipeline. sppLines Indices: Index Type Key or Field List primary key specObjID sppParams Indices: Index Type Key or Field List primary key specObjID
APOGEE Tables (DR10 and beyond)Back to Top These are the catalog data products for the Apache Point Observatory (APO) Galaxy Evolution Experiment survey.. apogeeDesign - This table contains all the design parameters used in designing plates for APOGEE spectra. apogeeField - This table contains the name, location and number of visits expected for an APOGEE field. apogeeObject - This table contains all the parameters that went into targeting objects for APOGEE spectra. apogeePlate - This table contains the parameters for an APOGEE spectral plate. apogeeStar - This table contains the data in the combined spectrum for an APOGEE star. apogeeVisit - This table corresponds to the data in a single spectrum visit in APOGEE. apogeeStarVisit - This is a linking table that links an APOGEE combined star spectrum with the visits that were used to create the combined spectrum. apogeeStarAllVisit - This is a version of the apogeeStarVisit table that includes all the visits for that star, including good, bad, commissioning, not, etc. aspcapStar - This table contains the data in the ASPCAP (Apogee Stellar Parameter and Chemical Abundances Pipeline) entry for an APOGEE star. aspcapStarCovar - This table contains selected covariance matrix fields for the ASPCAP entry for an APOGEE star.
MaNGA Tables (DR13 and beyond)Selected catalog data products from the Mapping Nearby Galaxies at APO survey are available as of DR13 in the following tables. More data will be available in future releases. There are links to the MaNGA data cubes in the Explore page for MaNGA objects.. mangaDrpAll - Final summary file of the MaNGA Data Reduction Pipeline (DRP). Contains all of the information required to find a given set of spectra for a target. mangaTarget - MaNGA Target Catalog. This table contains the details of the three main MaNGA samples, Primary, Secondary and Color-Enhanced, as well as the ancillary targets.
WISE Tables (DR12 and beyond)SDSS tables associated with the Wide-field Infrared Survey Explorer (WISE) are listed here. WISE_allsky - The WISE catalog. The columns have mostly been copied without modification from the WISE catalog distributed by IRSA, so that documentation (mostly copied here) largely applies. WISE_allsky Indices: Index Type Key or Field List primary key cntr covering index w1mpro covering index w2mpro covering index w3mpro covering index w4mpro covering index n_2mass covering index tmass_key covering index ra, dec covering index glat, glon covering index j_m_2mass covering index h_m_2mass covering index k_m_2mass covering index w1rsemi covering index blend_ext_flags covering index w1cc_map covering index w2cc_map covering index w3cc_map covering index w4cc_map covering index rjce WISE_xmatch - This is a 'join table' which contains 'pointers' to the matched objects in the SDSS and WISE tables. WISE_xmatch Indices: Index Type Key or Field List primary key sdss_objID, wise_cntr covering index wise_cntr wiseForcedTarget - (DR13 and beyond) This table contains WISE forced-photometry of SDSS primary sources. See here for the method. wiseForcedTarget Indices: Index Type Key or Field List primary key objID covering index ra, dec, has_wise_phot, treated_as_pointsource
BOSS Galaxy Product TablesThese are derived data products from the Baryon Oscillation Spectroscopic Survey. They each have a primary key index on specobjid. emissionLinesPort - Emission line kinematics results for BOSS galaxies using GANDALF. stellarMassPassivePort - Estimated stellar masses for BOSS galaxies using photometric method, assuming passive model. stellarMassStarformingPort - Estimated stellar masses for BOSS galaxies using photometric method, assuming a star-forming model. stellarMassPCAWiscBC03 and stellarMassPCAWiscM11 - Estimated stellar masses for BOSS galaxies using PCA technique.
Galaxy Zoo TablesThese are the results of galaxy classification from the Galaxy Zoo site: zooConfidence - Measures of classification confidence from Galaxy Zoo. zooMirrorBias - Results from the bias study using mirrored images from Galaxy Zoo. zooMonochromeBias - Results from the bias study that introduced monochrome images in Galaxy Zoo. zooNoSpec - Morphology classifications of galaxies without spectra from Galaxy Zoo. zooSpec - Morphological classifications of spectroscopic galaxies from Galaxy Zoo. zooVotes - Vote breakdown in Galaxy Zoo results.
Metadata and Other TablesDBObjects - An auto-generated documentation table that contains a description of every object (table, view, function, stored procedure) in the database. DBViewCols - An auto-generated table containing a description of every column in every table in the database. DBColumns - An auto-generated table containing a description of every column in every view in the database.
The Hierarchical Triangular Mesh (HTM)We have built a spatial indexing scheme called the Hierarchical Triangular Mesh (HTM) that spatially decomposes the region of the sky that is covered by the SDSS data and enables much faster spatial searches of the data by coordinate cuts.
Database IndicesIn addition to the HTM, which is an overall indexing scheme for multidimensional spatial data, the DBMS itself has the capability to define indices for fast searches on each table. We have defined indices on all the major tables. An index is a tree representation of a subset of the columns in a table that enables much faster searches of the table (compared to sequential scans of the table data) when constraints involving those columns are included in the query. All tables have an index on their primary key (unique row identifier), but the larger tables have indexes in addition to the primary key index. In all there are 3 kinds of indices: Primary Key Index - index on the unique primary key of a table. Foreign Key Index - index on a foreign key of a table, i.e. a column that is a primary key of another table. Covering Index - an index that covers one or more columns of a table. This is a combined index on those fields, so it speeds up searches if any of those fields are included in the WHERE clause. Click here to view a table of all the current indices defined on the data.