DR7 edition of the SDSS Quasar Catalog

The DR7 quasar catalog is described in Schneider et al. 2010. The catalog contains 105,783 objects from DR7 that have apparent i-band PSF magnitude fainter than 15, absolute i-band magnitudes brighter than -22, contain at least one emission line or are unambiguously broad absorption line quasars, and have highly reliable redshifts. The catalog was created by inspecting all spectra that were either targeted as quasar candidates, or classified as a quasar by the spectroscopic pipelines.

SDSS Quasar Catalog redshifts supersede those in other data products

Because of the re-inspection of the spectra, the DR7 Quasar Catalog provides the most reliable classifications and redshifts of SDSS quasars. The classifications in the catalog supersede those found in other data products accessible from the data access page, as well as from the DR5, DR3, DR1 and EDR quasar catalogs. The improved classifications will be fed back into other data products for future data releases.

The DR7 Quasar Catalog is not a statistical sample

There are two reasons:

1. It includes objects from all categories of target selection in SDSS, not just those selected as quasar candidates.

2. While the catalog contains both the TARGET selection flags used to select spectroscopic targets, and the BEST selection flags obtained by applying the final target selection version (sometimes to better photometric data obtained later during the survey), use of the BEST data produces a different set of quasar candidates than the TARGET version that was used to define spectroscopic plates, even for those parts of the sky that were targeted using the final quasar target selection algorithm described in Richards et al. 2002. If one uses the BEST photometry to define a statistical sample, not only must one drop catalog entries which were not selected by the final version, but one also has to account for missing quasar candidates, i.e., those identified by the final target selection algorithm but without spectroscopic observations. A forthcoming paper will discuss the construction of a statistical quasar sample in detail.

These caveats aside, the selection of UV excess quasars has remained reasonably uniform. These constitute 89% of the color-selected objects, and 63% of the total DR7 Catalog. Changes to the target selection algorithm were primarily aimed at improving the effectiveness of the identification of z> 2.5 quasars.

Download the DR7 Quasar Catalog

The catalog is available in the following formats:

• ASCII table
  • dr7qso.dat (51 MB)
  • dr7qso.dat.gz (gzipped, 13 MB)
• fits binary table
  • dr7qso.fit (56 MB)
  • dr7qso.fit.gz (13 MB)

The catalog files have been generated on March 30, 2010.