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Evidence for higher black hole spin in radio-loud quasars

Schulze, Andreas; Done, Chris; Lu, Youjun; Zhang, Fupeng; Inoue, Yoshiyuki

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Authors

Andreas Schulze

Youjun Lu

Fupeng Zhang

Yoshiyuki Inoue



Abstract

One of the major unsolved questions concerning the understanding of the active galactic nucleus population is the origin of the dichotomy between radio-quiet and radio-loud quasars. The most promising explanation is provided by the spin paradigm, which suggests that radio-loud quasars have a higher black hole spin. However, the measurement of black hole spin remains extremely challenging. We here aim at comparing the mean radiative efficiencies of carefully matched samples of radio-loud and radio-quiet Sloan Digital Sky Survey (SDSS) quasars at $0.3\lt z\lt 0.8$. We use the [O iii] luminosity as an indirect average tracer of the ionizing continuum in the extreme-UV regime where the differences in the spectral energy distribution (SED) due to black hole spin are most pronounced. We find that the radio-loud sample shows an enhancement in [O iii] line strength by a factor of at least 1.5 compared to a radio-quiet sample matched in redshift, black hole mass, and optical continuum luminosity or accretion rate. We argue that this enhancement is caused by differences in the SED, suggesting higher average bolometric luminosities at fixed accretion rate in the radio-loud population. This suggests that the radio-loud quasar population has on average systematically higher radiative efficiencies and therefore higher black hole spin than the radio-quiet population, providing observational support for the black hole spin paradigm.

Citation

Schulze, A., Done, C., Lu, Y., Zhang, F., & Inoue, Y. (2017). Evidence for higher black hole spin in radio-loud quasars. Astrophysical Journal, 849(1), Article 4. https://doi.org/10.3847/1538-4357/aa9181

Journal Article Type Article
Acceptance Date Oct 3, 2017
Online Publication Date Oct 24, 2017
Publication Date Oct 24, 2017
Deposit Date Oct 19, 2017
Publicly Available Date Mar 28, 2024
Journal Astrophysical Journal
Print ISSN 0004-637X
Electronic ISSN 1538-4357
Publisher American Astronomical Society
Peer Reviewed Peer Reviewed
Volume 849
Issue 1
Article Number 4
DOI https://doi.org/10.3847/1538-4357/aa9181

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Copyright Statement
© 2017. The American Astronomical Society. All rights reserved.






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