Getting redshift catalogs and all spectra and corresponding imaging data

Back to Spectra

For your convenience, we publish a variant of the DR4 spectroscopic data set which has all regular survey spectra and corresponding object lists entries and atlas images (i.e., these files do not include spectra from the "extra" plates with repeat observations, nor the spectra from the special plates). It consists of the following set of file for each plate of 640 fibers:

• spDiag-$mjd-$plate.par: the spectro1d summary
• spSpec-$mjd-$plate-$fiber.fit: the catalog of spectral lines per spectrum
• spPlate-$plate-$mjd.fits: the image of reduced spectra (1 spectrum per row)
• plPlugMapM-$plate-$mjd-$mapping.par: the mapping of targets to fibers
• spObj-$plate-$mjd-$rerun.fit: joined tsObj and spDiag and plPlugMap data for all fibers, hdu 1 = best, hdu 2 = target (these are called tsObjFromMap on the DAS download form)
• spAtlas-$plate-$mjd-$fiber.fit: best and target atlas images for all 5 colors for all fibers

The data model for a spObj file is a combination of data taken from the tsObj, spDiag and plPlugMap files. A tsObj file contains all imaging information for all objects (bright and faint) in a particular 0.033 sq. deg. imaging field, while a spObj file contains all imaging information for all fibers on a particular spectroscopic plate, with an area of 7 sq. deg. spanning many imaging fields.

You can access these files, as well as catalogs of just the redshifts, in bulk at the following locations:

The full set of plates

• one subdirectory per plate: http://das.sdss.org/DR4/data/spectro/ss_23
  An example of what is in these directories: plate 0666
• one tar.gz file of ~85MB per plate: http://das.sdss.org/DR4/data/spectro/ss_tar_23
  We recommend to use these. Most easily retrieved using wget or rsync, with the following command:

  rsync -vtrLPR rsync://dr4@rsync.sdss.org/DR4/spectro/ss_tar_23/ ./

  The password is dr4. Also see our rsync help page.

Just the redshifts

There are separate catalogs by spectroscopic classification, the gzipped tarballs are subdivided in to subsets for DR1+DR2 (suffix -DR2.fit.gz) and the incremental sets for DR3 and DR4 (suffix -DRx.fit.gz).

Galaxies

• All objects classified as galaxies: gals-DR2.fit.gz, 524M (DR1+DR2) gals-DR3.fit.gz, +241M (DR3 increment) gals-DR4.fit.gz, +220M (DR4 increment)
• Object from the tiled samples
  • Main galaxy sample: main_gals-DR2.fit.gz 438M, main_gals-DR3.fit.gz +202M (DR3 increment), main_gals-DR4.fit.gz +186M (DR4 increment)
  • Luminous Red Galaxies (LRGs): main_lrgs-DR2.fit.gz 49.3M, main_lrgs-DR3.fit.gz +23.7M, main_lrgs-DR4.fit.gz +24M

Quasars

• All objects classified as quasars: qsos-DR2.fit.gz 73M, qsos-DR3.fit.gz +30M, qsos-DR4.fit.gz +26M
• Only objects from the tiled main-survey quasar sample: main_qsos-DR2.fit.gz 44M, main_qsos-DR3.fit.gz +20M, main_qsos-DR4.fit.gz +18M

Note that there is a vetted DR3 quasar catalog presented by Schneider et al. 2005. The information contained in that catalog supersedes the information contained in all other data sources. We strongly recommend cross-checking the list given here against the Schneider et al. catalog. Future data releases will incorporate the information from the vetted quasar catalogs.

Stars

Objects classified as stars stars-DR2.fit.gz 98M, stars-DR3.fit.gz +46M, stars-DR4.fit.gz +37M

Unknown and sky fibers

Objects whose type could not be identified, and sky fibers used to perform sky subtraction from the spectra: unks-DR2.fit.gz 28M, unks-DR3.fit.gz 13M, unks-DR4.fit.gz 13M,

What about objects not observed due to fiber collisions?

You will want the tiling information.