C  <scp>iv</scp> wind properties of the SDSS-V X-ray selected quasars: strong optical-to-UV emission is key regardless of X-ray strength

ABSTRACT We present an investigation of the rest-frame optical/UV and X-ray properties for a sample of 3027 X-ray selected quasars between $1.5 \le z \le 3.5$ detected in the deepest Spectrum Roentgen Gamma/eROSITA data available and observed by the fifth iteration of the Sloan Digital Sky Survey (SDSS-V). We parametrize the C iv $\lambda 1549$ emission line to infer the strength of accretion disc winds and perform X-ray spectral fitting. The X-ray spectral properties – namely, the 2 keV monochromatic luminosity ($L_{2\, \text{keV}}$) and spectral slope – are not strongly correlated with wind strength. Despite this result, the X-ray selected sample is shifted towards lower C iv blueshifts and higher equivalent widths than the optically selected sample observed in previous SDSS surveys, and matching in optical luminosity, redshift, and Eddington ratio does not reduce these differences. We estimate the far-UV luminosity using the He ii $\lambda 1640$ line luminosity and define the slopes between this and the 2500 Å monochromatic luminosity ($L_{2500}$) and $L_{2\, \text{keV}}$ ($\alpha _\text{ouv}$ and $\alpha _\text{uvx}$, respectively) in a similar manner to the familiar $\alpha _\text{ox}$ parameter, which tracks the spectral slope between $L_{2500}$ and $L_{2\, \text{keV}}$. The quantity $\alpha _\text{ouv}$ is more strongly correlated with wind strength in our sample than $\alpha _\text{ox}$. We show that the correlation between $\alpha _\text{ox}$ and wind strength is driven by the relationship between the optical luminosity and wind strength. Our results are consistent with a radiation line-driven wind, whereby the ionizing far-UV photons must not over-ionize the gas. The hard X-ray photons are few enough in number to have a negligible effect on the ionization state of the material.

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Journal
Monthly Notices of the Royal Astronomical Society
Published
2026-04-17
DOI
https://doi.org/10.1093/mnras/stag734
Primary Topic
Astrophysical Phenomena and Observations
Type
article
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article

C  iv wind properties of the SDSS-V X-ray selected quasars: strong optical-to-UV emission is key regardless of X-ray strength

James Aird, Sean Morrison, Scott F. Anderson, B. Musiimenta et al.
Monthly Notices of the Royal Astronomical Society
Astrophysical Phenomena and Observations
article

C  iv wind properties of the SDSS-V X-ray selected quasars: strong optical-to-UV emission is key regardless of X-ray strength

James Aird, Sean Morrison, Scott F. Anderson, B. Musiimenta, Patrick B. Hall, T Liu, M. Salvato, D. Tubín-Arenas, Anton M. Koekemoer, Qingling Ni, Amy L. Rankine, Dominika Wylezalek, Maria Chira, Paola Rodríguez Hidalgo, Pranavi Hiremath, C A Negrete, Marcella Brusa, Mirko Krumpe Georg Lamer, Roberto J Assef, David Homan, Johannes Buchner, Donald P Schneider, Yue Shen, W N Brandt, Matthew J Temple, Franz E Bauer, Yaherlyn Díaz
article en

Abstract

ABSTRACT We present an investigation of the rest-frame optical/UV and X-ray properties for a sample of 3027 X-ray selected quasars between $1.5 \le z \le 3.5$ detected in the deepest Spectrum Roentgen Gamma/eROSITA data available and observed by the fifth iteration of the Sloan Digital Sky Survey (SDSS-V). We parametrize the C iv $\lambda 1549$ emission line to infer the strength of accretion disc winds and perform X-ray spectral fitting. The X-ray spectral properties – namely, the 2 keV monochromatic luminosity ($L_{2\, \text{keV}}$) and spectral slope – are not strongly correlated with wind strength. Despite this result, the X-ray selected sample is shifted towards lower C iv blueshifts and higher equivalent widths than the optically selected sample observed in previous SDSS surveys, and matching in optical luminosity, redshift, and Eddington ratio does not reduce these differences. We estimate the far-UV luminosity using the He ii $\lambda 1640$ line luminosity and define the slopes between this and the 2500 Å monochromatic luminosity ($L_{2500}$) and $L_{2\, \text{keV}}$ ($\alpha _\text{ouv}$ and $\alpha _\text{uvx}$, respectively) in a similar manner to the familiar $\alpha _\text{ox}$ parameter, which tracks the spectral slope between $L_{2500}$ and $L_{2\, \text{keV}}$. The quantity $\alpha _\text{ouv}$ is more strongly correlated with wind strength in our sample than $\alpha _\text{ox}$. We show that the correlation between $\alpha _\text{ox}$ and wind strength is driven by the relationship between the optical luminosity and wind strength. Our results are consistent with a radiation line-driven wind, whereby the ionizing far-UV photons must not over-ionize the gas. The hard X-ray photons are few enough in number to have a negligible effect on the ionization state of the material.

Monthly Notices of the Royal Astronomical SocietyVol. 548(4)
University of Science and Technology of China (CN), Space Telescope Science Institute (US), Pennsylvania State University (US), University of Illinois Urbana-Champaign (US), University of Tarapacá (CL), Durham University (GB), York University (CA), University of Washington (US), Heidelberg University (DE), University of Cambridge (GB), Leibniz Institute for Astrophysics Potsdam (DE), Astronomical Observatory of Rome (IT), Istituto di Astrofisica Spaziale e Fisica Cosmica di Bologna (IT), Max Planck Institute for Extraterrestrial Physics (DE), Royal Observatory (GB), Université Bourgogne Franche-Comté (FR), National Observatory of Athens (GR), Institute of Astronomy (RU), National Center for Supercomputing Applications (US), University of Washington Bothell (US), Seattle University (US), Heidelberg Institute for Theoretical Studies (DE), Federico Santa María Technical University (CL), National Institute for Astrophysics (IT), Universidad Nacional Autónoma de México (MX), Universidad Diego Portales (CL), University of Bologna (IT), University of Edinburgh (GB)
National Science Foundation, National Aeronautics and Space Administration, Yale University, Ohio State University, University of Utah, Pennsylvania State University, University of Virginia, New Mexico State University, UK Research and Innovation, University of Toronto, Yunnan University, Hellenic Foundation for Research and Innovation, Agencia Nacional de Investigación y Desarrollo, Science and Technology Facilities Council, National Astronomical Observatories, Chinese Academy of Sciences, Fondo Nacional de Desarrollo Científico y Tecnológico
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