Unusual Broad Absorption Line Quasars from the Sloan Digital Sky Survey

By P. Hall, S. Anderson, M. Strauss, D. York, Gordon Richards, Xiaohui Fan, G. Knapp, D. Schneider, D. V. vanden Berk, T. Geballe and 43 more. 2002

303 citations recorded by the source corpus.

The Sloan Digital Sky Survey has confirmed the existence of populations of broad absorption line (BAL) quasars with various unusual properties. We present and discuss 23 such objects and consider the implications of their wide range of properties for models of BAL outflows and quasars in general. We have discovered one BAL quasar with a record number of absorption lines. Two other similarly complex objects with many narrow troughs show broad Mg II absorption extending longward of their systemic host galaxy redshifts. This can be explained as absorption of an extended continuum source by the rotation-dominated base of a disk wind. Five other objects have absorption that removes an unprecedented ∼90% of all flux shortward of Mg II. The absorption in one of them has varied across the ultraviolet with an amplitude and rate of change as great as ever seen. This same object may also show broad Hβ absorption. Numerous reddened BAL quasars have been found, including at least one reddened mini-BAL quasar with very strong Fe II emission. The five reddest objects have continuum reddenings of E(B-V) ≃ 0.5, and in two of them we find strong evidence that the reddening curve is even steeper than that of the SMC. We have found at least one object with absorption from Fe III but not Fe II. This may be due to a high column density of moderately high ionization gas, but the Fe III level populations must also be affected by some sort of resonance. Finally, we have found two luminous, probably reddened high-redshift objects that may be BAL quasars whose troughs partially cover different regions of the continuum source as a function of velocity.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/f545f2b01d246c440a679803374c6563f0019f96

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Citations in the corpus

THE ULTRAVIOLET-BRIGHT, SLOWLY DECLINING TRANSIENT PS1-11af AS A PARTIAL TIDAL DISRUPTION EVENT (2013, background): “The typical shapes of the absorption troughs in BALQSOs (e.g., Voit et al. 1993; Hall et al. 2002) are generally quite different from the single broad absorption with a smooth profile for each line in PS111af.”
Candidate Type II Quasars from the Sloan Digital Sky Survey. I. Selection and Optical Properties of a Sample at 0.3 < Z < 0.83 (2003, background): “Dereddening has been discussed as an alternative way to estimate obscuration even for heavily reddened objects (e.g., Hall et al. 2002).”
Red and Reddened Quasars in the Sloan Digital Sky Survey (2003, methodology): “Even more heavily reddened and/or obscured quasars, including broad absorption line quasars (BALQSOs), such as those presented by Hall et al. (2002a), may not always be classified as quasars by the automated SDSS pipelines as a result of their unusual spectra (see x 3.4).”
The Lyα Forest Power Spectrum from the Sloan Digital Sky Survey (2004, background): “All of these differences are easy to understand: First, BALs are known to be strongest in CIV absorption (Hall et al. (2002)), so it is not surprising that we see the effects of BALs primarily in this wavelength region.”
THE SLOAN DIGITAL SKY SURVEY QUASAR CATALOG. V. SEVENTH DATA RELEASE (2010, background): “The spectra in the third category often have low signal-to-noise ratio (S/N) or some glaring instrumentinduced defects, but the set of UNKNOWN objects also include a considerable number of quasars that would have been missed by the other three selection criteria (e.g., extreme BALs; Hall et al. 2002”
Dynamics of Line-driven Disk Winds in Active Galactic Nuclei. II. Effects of Disk Radiation (2000, result): “Our line profiles are consistent with many of the properties of profiles observed in broad absorption line QSOs (e.g., Korista et al. 1993; Hall et al. 2002).”
The HDUV Survey: A Revised Assessment of the Relationship between UV Slope and Dust Attenuation for High-redshift Galaxies (2017, background): “…average have been observed along certain sightlines within the SMC (Gordon et al. 2003), in the Milky Way and some Local Group galaxies (Gordon et al. 2003; Sofia et al. 2005; Gordon et al. 2009; Amanullah et al. 2014), and in quasars (e.g., Hall et al. 2002; Jiang et al. 2013; Zafar et al. 2015).”
The Sloan Digital Sky Survey Quasar Catalog: Sixteenth Data Release (2020, methodology): “The algorithm measured the commonly used “BALnicity index” (BI) proposed by Weymann et al. (1991) and the intrinsic absorption index (AI) proposed by Hall et al. (2002).”
A Catalog of Broad Absorption Line Quasars from the Sloan Digital Sky Survey Early Data Release (2003, background): “The “absorption index” (AI) was first proposed by Hall et al. (2002).”
THE BARYON OSCILLATION SPECTROSCOPIC SURVEY OF SDSS-III (2012, methodology): “BAL quasars are processed for automatic estimates of the balnicity index (BI; Weymann et al. 1991) and absorption index (AI; Hall et al. 2002) of C IV troughs to quantify their strength.”
The Sloan Digital Sky Survey quasar catalog: ninth data release (2012, methodology): “In order to detect BALs and to characterize the strength of the troughs using an objective procedure, we compute the balnicity (BI, Weymann et al. 1991) and the absorption indices (AI, Hall et al. 2002) of the Civ troughs.”
The Third Data Release of the Sloan Digital Sky Survey (2004, background): “Many of these objects are of low signal-to-noise ratio, or are unusual objects of various types, especially unusual quasars (see Hall et al. 2002).”
A CATALOG OF BROAD ABSORPTION LINE QUASARS IN SLOAN DIGITAL SKY SURVEY DATA RELEASE 5 (2008, background): “The depth of absorption at a given outflow velocity is largely determined by the fraction of the UV emission region covered by the BAL outflow (e.g., Arav et al. 1999a, and see also Appendix A of Hall et al. 2002), and is therefore an indicator of the outflow structure.”
THE QUASAR OUTFLOW CONTRIBUTION TO AGN FEEDBACK: VLT MEASUREMENTS OF SDSS J0318-0600 (2009, methodology): “In a survey by Hall et al. (2002), it was classified as an iron lowionization broad absorption line system (FeLoBAL) and listed as an unusual quasar due to the BAL located at ∼27,000 km s−1 and the system of NALs, which appears as a BAL in higher ionization lines such as C iv.”
A strong redshift dependence of the broad absorption line quasar fraction (2010, background): “Modifications to the BI have been proposed, in particular the absorption index (AI; Hall et al. 2002; Trump et al. 2006), designed to include narrower troughs than the BI, and the modified balnicity index BI0 (Gibson et al. 2009, hereafter G09), which extends the integration region to zero velocity.”
The Sloan Digital Sky Survey Quasar Catalog. IV. Fifth Data Release (2007, background): “The SDSS has discovered a wide variety of extreme BAL quasars (see Hall et al. 2002); Figure 1 (bottom right) presents the spectrum of an unusual FeLoBAL quasar with strong Balmer absorption (see Hall 2007 for a discussion of this object).”
Quasar outflows and AGN feedback in the extreme UV: HST/COS observations of HE 0238−1904 (2013, background): “Alternatively, Hall et al. (2002); Dunn et al. (2010a) argue that Ω for both forms of outflows are the same and that the rarity of lower ionization outflows is due to line of sight effects.”
The Sloan Digital Sky Survey Quasar Catalog. II. First Data Release (2003, background): “Finally, the SDSS has also demonstrated that it can identify an appreciable number of ‘‘ extreme BALs ’’; 18 of the 23 unusual BALs presented in Hall et al. (2002a) are in the DR1 catalog.”
The Nuclear Reddening Curve for Active Galactic Nuclei and the Shape of the Infrared to X-Ray Spectral Energy Distribution (2003, background): “Our reddening curve might similarly explain the unusual spectral shapes of some broad absorption line quasars without the need to invoke partial covering (see Hall et al. 2002).”