A new sample of broad-absorption-line quasars exhibiting the ghost of lyman alpha

Abstract

We have searched the broad-absorption-line quasar (BAL QSO) sample presented by Reichard et al. for objects exhibiting the so-called `ghost of Lyman alpha'. This ghost manifests as a hump near -5900kms in the troughs of the broad absorption lines and provides strong evidence for the importance of line-driving in powering the outflows from BAL QSOs. Of the 224 sample BAL QSOs selected from the Sloan Digital Sky Survey (SDSS) Early Data Release (EDR), 198 satisfy our redshift constraints and 58 show clear evidence of multiple-trough (MT) structure in the CIV line. A composite spectrum constructed from this MT sample already shows evidence for a ghost feature. Narrowing our classification scheme further, we define a set of 36 objects that individually show evidence of a ghost feature, and then apply further cuts to arrive at a final `best sample' that contains our seven strongest ghost candidates. A further five objects show evidence for a ghost feature that is almost strong enough to merit inclusion in our best sample. Despite its limited size, our best sample more than doubles the number of known BAL QSOs with clear ghost signatures and should make an excellent basis for detailed follow-up studies.

arXiv comment11 pages, 7 figures, accepted for publication in MNRAS

References in corpus (4)

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• Continuum and Emission-Line Properties of Broad Absorption Line Quasars
• The Sloan Digital Sky Survey Quasar Catalog I. Early Data Release
• A Catalog of Broad Absorption Line Quasars from the Sloan Digital Sky Survey Early Data Release

Cited by in corpus (11)

• The Intrinsic Fraction of Broad Absorption Line Quasars
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• A Simple Disk Wind Model for Broad Absorption Line Quasars
• Classifying Broad Absorption Line Quasars: Metrics, Issues and a New Catalogue Constructed from SDSS DR5
• Photoionization calculations of the radiation force due to spectral lines in AGNs
• The origin of radio emission in broad absorption line quasars: Results from the LOFAR Two-metre Sky Survey
• The Ubiquitous Imprint of Radiative Acceleration in the Mean Absorption Spectrum of Quasar Outflows
• Quasar emission lines as probes of orientation: implications for disc wind geometries and unification
• Narrow Absorption Lines Complex. II. Probing the Line-locking Signatures within the Trough-like Broad Absorption Line
• Searching for the signature of radiative line driving: On the absence of Ly-alpha-N V line-locking features in a large sample of BALQSOs
• Astrophysics in 2006