SDSS DR13 Optical Spectra Catalog
(Latest revision: 22 July 2017)
The Sloan Digital Sky Survey (SDSS) Data Release 13 (DR13) Optical Spectra Catalog was obtained (in FITS format) from http://www.sdss.org/dr13/data_access/bulk/.
Format: SDSS JHHMMSS.ss+/-DDMMSS.s
Example: SDSS J133840.44+481704.9
1) The fields SPECOBJID, MJD, PLUG_RA, PLUG_DEC, SOURCETYPE, SUBCLASS, Z, and Z_ERR were used for processing.
2) The original catalog did not contain names in the SDSS JHHMMSS.ss+DDMMSS.s format.
The decimal degree coordinates were transformed into sexigesimal (via dd2sex) and
modified to fit the standard format. Names which match SDSS names already in NED
were considered to be matches. Newly created names which were "slight variants"
to SDSS names already in NED were attached as new aliases. Newly created SDSS
names matched with non-SDSS objects had the SDSS name attached as an alias. SDSS
objects without a NED counterpart were added as new objects.
3) Approximately 10% of the original catalog (400,000 sources) consists of entries for
"SKY" observations or for which the fiber was "UNPLUGGED". These were removed
from the input file used for cross-matching with objects in NED.
4) Many redshift uncertainties are quite unrealistic (e.g., uncertainty values >10) in
the original catalog. Redshift uncertainties which are greater than the redshift
itself have been replaced with a blank/null value in NED.
5) Many objects were observed more than once (in particular, the
SDSS-Reverberation Mapping catalog, Shen et al. 2015). All redshifts for a
given object have been retained in NED's detailed data frames.
6) When more than one redshift is provided for the same object, the redshift with the lowest non-zero uncertainty was determined to be the "preferred" value.
7) Of the 4,411,200 records in the original catalog, there are:
- 3,981,490 unique objects
- 429,709 objects have multiple redshifts
- 367,812 were flagged as "SKY" or "UNPLUGGED". They were not promoted as objects.
- 26,370 had unrealistic redshift uncertainties changed to nulls
- 2,622,404 records are classified as Galaxy
- 1,010,968 records are classified as Star
- 777,828 records are classified as QSO
- 1,892,798 names matched objects previously in NED (May 2017)
- 1,362,366 new aliases added to objects previously in NED (May 2017)
- 650,874 new objects added to NED (May 2017)
- 1,524,894 objects previously in NED with redshifts had SDSS DR13 redshifts added (June 2017)
- 1,805,722 objects previously in NED without redshifts had SDSS DR13 redshifts added (June 2017)