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Description
This table contains a catalog of 5035 broad absorption line (BAL) quasars (QSOs) in the Sloan Digital Sky Survey (SDSS) Data Release 5 (DR5) QSO catalog that have absorption troughs covering a continuous velocity range greater than or equal to 2000 km s<sup>-1</sup>. The authors have fitted ultraviolet (UV) continua and line emission in each case, enabling them to report common diagnostics of BAL strengths and velocities in the range from -25,000 to 0 km s<sup>-1</sup> for Si IV 1400 Angstroms, C IV 1549 A, Al III 1857 A, and Mg II 2799 A. The authors calculate these diagnostics using the spectrum listed in the DR5 QSO catalog, and also for spectra from additional SDSS observing epochs when available. They confirm and extend previous findings that BAL QSOs are more strongly reddened in the rest-frame UV than non-BAL QSOs, and that BAL QSOs are relatively X-ray weak compared to non-BAL QSOs. The observed BAL fraction is dependent on the spectral signal-to-noise ratio (S/N); for higher S/N sources, the authors find an observed BAL fraction of about 15%. BAL QSOs show a similar Baldwin effect as for non-BAL QSOs, in that their C IV emission equivalent widths decrease with increasing continuum luminosity. However, BAL QSOs have weaker C IV emission in general than do non-BAL QSOs. Sources with higher UV luminosities are more likely to have higher-velocity outflows, and the BAL outflow velocity and UV absorption strength are correlated with relative X-ray weakness. These results are in qualitative agreement with models that depend on strong X-ray absorption to shield the outflow from overionization and enable radiative acceleration. In a scenario in which BAL trough shapes are primarily determined by outflow geometry, observed differences in Si IV and C IV trough shapes would suggest that some outflows have ion-dependent structure. The authors fit SDSS spectra using the algorithm of Gibson et al. (2008, ApJ, 675, 985), which we summarize here. For QSOs at z >= 1.7, their continuum model is a power law reddened using the Small Magellanic Cloud (SMC) reddening curve of Pei (1992, ApJ, 395, 130). For QSOs at lower redshifts, the authors use a fourth- or sixth-degree polynomial; in their experience this nonphysical model is able to reproduce well the complex continuum at longer wavelengths. They initially fit regions that are generally free from strong absorption or emission features: 1250-1350, 1700-1800, 1950-2200, 2650-2710, 2950-3700, 3950-4050, 4140-4270, 4400-4800, 5100-6400, and > 6900 Angstroms. They then iteratively fit the continuum, ignoring at each step wavelength bins that deviate by more than 3 sigma from the current fit in order to exclude strong absorption and emission features. They fit Voigt profiles to the strongest emission lines expected in the spectrum: Si IV 1400, C IV 1549, Al III 1857, C III 1909, and Mg II 2799. These wavelengths are taken from the SDSS vacuum wavelength list used by the SDSS pipeline to determine emission-line redshifts. Much more information on the SDSS is available at the project's web site at <a href="http://www.sdss.org/">http://www.sdss.org/</a>. This table was created by the HEASARC in April 2009 based on the machine-readable version of Table 1 from the reference paper obtained from the ApJ web site. This is a service provided by NASA HEASARC .
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