X-ray selected broad absorption line quasars in SDSS-V: BALs and non-BALs span the same range of X-ray properties

ABSTRACT Broad absorption line (BAL) quasars are often considered X-ray weak relative to their optical/UV luminosity, whether intrinsically (i.e. the coronal emission is fainter) or due to large column densities of absorbing material. The SDSS-V is providing optical spectroscopy for samples of quasar candidates identified by eROSITA as well as Chandra, XMM, or Swift, making the resulting data sets ideal for characterizing the BAL quasar population within an X-ray selected sample. We use the Balnicity Index (BI) to identify the BAL quasars based on absorption of the C iv$\lambda \, 1549$ emission line in the optical spectra, finding 143 BAL quasars in our sample of 2317 X-ray selected quasars within $1.5\le z \le 3.5$. This observed BAL fraction of $\approx$ 6 per cent is comparable to that found in optically selected samples. We also identify absorption systems via the Absorption Index (AI) which includes mini-BALs and NALs, finding 954 quasars with AI $>0$. We consider the C iv emission space (equivalent width versus blueshift) to study the BAL outflows within the context of the radiatively driven accretion disc–wind model. X-ray selection excludes the highest outflow velocities in emission but includes the full range of absorption velocities which we suggest is consistent with the BAL gas being located further from the X-ray corona than the emitting gas. We observe both X-ray weak and X-ray strong BALs (via the optical-to-X-ray spectral slope, $\alpha _\text{ox}$) and detect little evidence for differing column densities between the BAL and non-BAL quasars, suggesting the BALs and non-BALs have the same shielding gas and intrinsic X-ray emission.

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Journal
Monthly Notices of the Royal Astronomical Society
Published
2025-08-15
DOI
https://doi.org/10.1093/mnras/staf1352
Citations
1
Primary Topic
Astrophysical Phenomena and Observations
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article
Field-Weighted Citation Impact
1.15

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article

X-ray selected broad absorption line quasars in SDSS-V: BALs and non-BALs span the same range of X-ray properties

James Aird, Sean Morrison, Donald P. Schneider, W. N. Brandt et al.
1 citations
Monthly Notices of the Royal Astronomical Society
Astrophysical Phenomena and Observations
1.15
article

X-ray selected broad absorption line quasars in SDSS-V: BALs and non-BALs span the same range of X-ray properties

James Aird, Sean Morrison, Donald P. Schneider, W. N. Brandt, Cláudio Ricci, Scott F. Anderson, M. Salvato, Catarina Aydar, Pranoti Hiremath, Zsofi Igo, Amy L. Rankine, Paola Rodríguez Hidalgo, M. Vivek
article en
1 citations

Abstract

ABSTRACT Broad absorption line (BAL) quasars are often considered X-ray weak relative to their optical/UV luminosity, whether intrinsically (i.e. the coronal emission is fainter) or due to large column densities of absorbing material. The SDSS-V is providing optical spectroscopy for samples of quasar candidates identified by eROSITA as well as Chandra, XMM, or Swift, making the resulting data sets ideal for characterizing the BAL quasar population within an X-ray selected sample. We use the Balnicity Index (BI) to identify the BAL quasars based on absorption of the C iv$\lambda \, 1549$ emission line in the optical spectra, finding 143 BAL quasars in our sample of 2317 X-ray selected quasars within $1.5\le z \le 3.5$. This observed BAL fraction of $\approx$ 6 per cent is comparable to that found in optically selected samples. We also identify absorption systems via the Absorption Index (AI) which includes mini-BALs and NALs, finding 954 quasars with AI $>0$. We consider the C iv emission space (equivalent width versus blueshift) to study the BAL outflows within the context of the radiatively driven accretion disc–wind model. X-ray selection excludes the highest outflow velocities in emission but includes the full range of absorption velocities which we suggest is consistent with the BAL gas being located further from the X-ray corona than the emitting gas. We observe both X-ray weak and X-ray strong BALs (via the optical-to-X-ray spectral slope, $\alpha _\text{ox}$) and detect little evidence for differing column densities between the BAL and non-BAL quasars, suggesting the BALs and non-BALs have the same shielding gas and intrinsic X-ray emission.

Monthly Notices of the Royal Astronomical SocietyVol. 542(3)
Pennsylvania State University (US), Indian Institute of Astrophysics (IN), University of Illinois Urbana-Champaign (US), University of Washington (US), Peking University (CN), Heidelberg University (DE), Max Planck Institute for Extraterrestrial Physics (DE), Excellence Cluster Origins (DE), Royal Observatory (GB), Kavli Institute for Theoretical Sciences (CN), University of Washington Bothell (US), Seattle University (US), Universidad Diego Portales (CL), University of Edinburgh (GB)
National Science Foundation, Smithsonian Institution, Alfred P. Sloan Foundation, Yale University, Carnegie Institution of Washington, University of Pennsylvania, Ohio State University, California Institute of Technology, Harvard University, Johns Hopkins University, Pennsylvania State University, New Mexico State University, Space Telescope Science Institute, UK Research and Innovation, Flatiron Health, Leverhulme Trust, Deutsche Forschungsgemeinschaft, École Polytechnique Fédérale de Lausanne, Eberhard Karls Universität Tübingen, University of Toronto, Max-Planck-Gesellschaft, Universität Hamburg, Universidad Nacional Autónoma de México, Yunnan University, Nanjing University, Rheinische Friedrich-Wilhelms-Universität Bonn, China National Textile and Apparel Council, Leibniz-Institut für Astrophysik Potsdam, Agencia Nacional de Investigación y Desarrollo, Max-Planck-Institut für Astronomie, University of Illinois at Urbana-Champaign, University of Colorado Boulder, Smithsonian Astrophysical Observatory, Leibniz-Gemeinschaft, Russian Academy of Sciences, National Astronomical Observatories, Chinese Academy of Sciences
Openalex Percentile: Top 17%
Astrophysical Phenomena and Observations
1.15
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