Using the Properties of Broad Absorption Line Quasars to Illuminate Quasar Structure
Autor: | A. L. King, Kathleen Labrie, Matthew O'Dowd, Rachel L. Webster, Nicholas F. Bate, Suk Yee Yong |
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Rok vydání: | 2018 |
Předmět: |
Absolute magnitude
Active galactic nucleus Cosmology and Nongalactic Astrophysics (astro-ph.CO) Astrophysics::High Energy Astrophysical Phenomena Population FOS: Physical sciences Astrophysics Astrophysics::Cosmology and Extragalactic Astrophysics 01 natural sciences Spectral line 0103 physical sciences Emission spectrum education 010303 astronomy & astrophysics Astrophysics::Galaxy Astrophysics Physics Spectral index education.field_of_study 010308 nuclear & particles physics Astronomy and Astrophysics Quasar Astrophysics - Astrophysics of Galaxies Redshift 13. Climate action Space and Planetary Science Astrophysics of Galaxies (astro-ph.GA) Astrophysics - Cosmology and Nongalactic Astrophysics |
DOI: | 10.48550/arxiv.1806.07090 |
Popis: | A key to understanding quasar unification paradigms is the emission properties of broad absorption line quasars (BALQs). The fact that only a small fraction of quasar spectra exhibit deep absorption troughs blueward of the broad permitted emission lines provides a crucial clue to the structure of quasar emitting regions. To learn whether it is possible to discriminate between the BALQ and non-BALQ populations given the observed spectral properties of a quasar, we employ two approaches: one based on statistical methods and the other supervised machine learning classification, applied to quasar samples from the Sloan Digital Sky Survey. The features explored include continuum and emission line properties, in particular the absolute magnitude, redshift, spectral index, line width, asymmetry, strength, and relative velocity offsets of high-ionisation CIV $\lambda 1549$ and low-ionisation MgII $\lambda 2798$ lines. We consider a complete population of quasars, and assume that the statistical distributions of properties represent all angles where the quasar is viewed without obscuration. The distributions of the BALQ and non-BALQ sample properties show few significant differences. None of the observed continuum and emission line features are capable of differentiating between the two samples. Most published narrow disk-wind models are inconsistent with these observations, and an alternative disk-wind model is proposed. The key feature of the proposed model is a disk-wind filling a wide opening angle with multiple radial streams of dense clumps. Comment: Accepted for publication in MNRAS. 19 pages, 3 figures, 6 table |
Databáze: | OpenAIRE |
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