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SDSSBALQSO - Sloan Digital Sky Survey Broad Absorption Line Quasars Catalog (3rd Data Release)



The Sloan Digital Sky Survey (SDSS) Broad Absorption Line (BAL) Quasars Catalog (based on the 3rd SDSS Data Release) contains a total of 4784 unique BAL quasars from the SDSS DR3 (CDS Cat. <VII/243>). An automated algorithm was used to match a continuum to each quasar and to identify regions of flux at least 10% below the continuum over a velocity range of at least 1000 km/s in the C IV and Mg II absorption regions. The model continuum was selected as the best-fit match from a set of template quasar spectra binned in luminosity, emission line width, and redshift z, with the power-law spectral index and amount of dust reddening as additional free parameters. The authors characterize their sample through the traditional 'balnicity' index BI and a revised absorption index AI, as well as through parameters such as the width, outflow velocity, fractional depth, and number of troughs. From a sample of 16,883 quasars at 1.7 <= z <= 4.38, they identify 4386 (26.0%) quasars with broad C IV absorption, of which 1756 (10.4%) satisfy traditional selection criteria. From a sample of 34,973 quasars at 0.5 <= z <= 2.15, they identify 457 (1.31%) quasars with broad Mg II absorption, 191 (0.55%) of which satisfy traditional selection criteria. They find that BAL quasars may have broader emission lines on average than other quasars.

Much more information on the SDSS is available at the project's web site at

Catalog Bibcode



A catalog of broad absorption line quasars from the Sloan Digital Sky Survey
third data release.
    Trump J.R., Hall P.B., Reichard T.A., Richards G.T., Schneider D.P.,
    Vanden Berk D.E., Knapp G.R., Anderson S.F., Fan X., Brinkman J.,
    Kleinman S.J., Nitta A.
   <Astrophys. J. Suppl. Ser., 165, 1-18 (2006)>


This table was created by the HEASARC in July 2008 based on CDS catalog J/ApJS/165/1 file table4.dat.


The SDSS DR3 source designation in the standard format, e.g., 'SDSS'.

The Right Ascension of the quasar in the selected equinox. This was given in J2000 decimal degrees to a precision of 0.01 seconds of time (implicitly in the name field) in the original table.

The Declination of the quasar in the selected equinox. This was given in J2000 decimal degrees to a precision of 0.1 arcseconds (implicitly in the name field) in the original table.

The Galactic Longitude of the quasar.

The Galactic Latitude of the quasar.

The SDSS spectroscopic plate number.

The date of the SDSS spectroscopic observation (converted by the HEASARC from Modified Julian Date (MJD) to the actual date).

The SDSS spectroscopic fiber number.

The redshift of the quasar.

The SDSS PSF i magnitude (not corrected for Galactic extinction) of the quasar.

The absolute i magnitude of the quasar.

The BAL subtype of the quasar, as follows:

       n  = relatively narrow trough
      LoF = FeLoBAL with MgII absorption in its SDSS spectra
      HLF = FeLoBAL with CIV absorption in its SDSS spectra
       Lo = LoBAL detected through MgII absorption
       HL = HiBAL in which broad (>=1000km/s) low-ionization absorption is
            also seen
       Hi = HiBAL-only object, in which broad low-ionization absorption is
            not seen even though MgII is within the spectral coverage
        H = HiBAL in which the MgII region is not within the spectral
            coverage or has a very low signal-to-noise ratio and so whether
            or not the object is a LoBAL as well as a HiBAL is unknown
For further details, see Section 5 of the reference paper.

The absorption index AI of the quasar, being the true equivalent width in km/s, measuring all absorption within the limits of every trough, and so that the integration limit extends to 29,000 km/s. For further details, see Section 4.3 of the reference paper.

The error in the absorption index AI, in km/s.

The balnicity index BI of the quasar, BI is a modified equivalent width of the C IV BAL, being the sum of the 'modified equivalent widths' of the portions of all contiguous BAL troughs between 3,000 and 25,000 km/s shortward of 1549 Angstroms. For further details, see Section 4.1 of the reference paper.

The error in the balnicity index BI, in km/s.

The best-fitting template number for the quasar spectrum. Template numbers 0-3 correspond to the less luminous bin and numbers 4-7 to the more luminous bin; line width increases from 0 to 3 and from 4 to 7. For further details, see Section 3 of the reference paper

The spectral index alpha_nu used by the best-fit template.

The reddening E(B-V) used by the best-Fit template.

The reduced Chi2 value of the best fit.

The number of distinct BAL troughs.

The width of the widest BAL trough, in km/s.

The fractional depth of the deepest part of any BAL trough.

The weighted average velocity of the BAL troughs, in km/s.

The maximum velocity of the BAL troughs from the emission line, in km/s.

The SDSS spectrum signal-to-noise ratio (SNR) in the i-band.

Contact Person

Questions regarding the SDSSBALQSO database table can be addressed to the HEASARC User Hotline.

Page Author: Browse Software Development Team
Last Modified: 27-Apr-2009