BAL and non-BAL quasars: Continuum, emission, and absorption properties establish a common parent sample
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Publication Date
2020-03-01Journal Title
Monthly Notices of the Royal Astronomical Society
ISSN
0035-8711
Publisher
Oxford University Press
Issue
3
Pages
4553-4575
Type
Article
This Version
AM
Metadata
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Rankine, A., Hewett, P., Banerji, M., & Richards, G. (2020). BAL and non-BAL quasars: Continuum, emission, and absorption properties establish a common parent sample. Monthly Notices of the Royal Astronomical Society, (3), 4553-4575. https://doi.org/10.1093/mnras/staa130
Abstract
Using a sample of $\simeq$144,000 quasars from the Sloan Digital Sky Survey data release 14 we investigate the outflow properties, evident both in absorption and emission, of high-ionization Broad Absorption Line (BAL) and non-BAL quasars with redshifts 1.6 $\lesssim z \leq$ 3.5 and luminosities 45.3 $< \log_{10}(L_{bol}) < $ 48.2 erg s$^{-1}$. Key to the investigation is a continuum and emission-line reconstruction scheme, based on mean-field independent component analysis, that allows the kinematic properties of the CIV$\lambda$1550 emission line to be compared directly for both non-BAL and BAL quasars. CIV-emission blueshift and equivalent-width (EW) measurements are thus available for both populations. Comparisons of the emission-line and BAL-trough properties reveal strong systematic correlations between the emission and absorption properties. The dependence of quantitative outflow indicators on physical properties such as quasar luminosity and luminosity relative to Eddington-luminosity are also shown to be essentially identical for the BAL and non-BAL populations. There is an absence of BALs in quasars with the hardest spectral energy distributions (SEDs), revealed by the presence of strong HeII$\lambda$1640 emission, large CIV$\lambda$1550-emission EW and no measurable blueshift. In the remainder of the CIV-emission blueshift versus EW space, BAL and non-BAL quasars are present at all locations; for every BAL-quasar it is possible to identify non-BAL quasars with the same emission-line outflow properties and SED-hardness. The co-location of BAL and non-BAL quasars as a function of emission-line outflow and physical properties is the key result of our investigation, demonstrating that (high-ionization) BALs and non-BALs represent different views of the same underlying quasar population.
Sponsorship
SCIENCE & TECHNOLOGY FACILITIES COUNCIL (ST/N000927/1)
Identifiers
External DOI: https://doi.org/10.1093/mnras/staa130
This record's URL: https://www.repository.cam.ac.uk/handle/1810/300511
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